1 THIN SPRAY-ON LXNJZR SUPPORT & IMPLEMENTATION IN THE HARDROCK MINLNG INDUSTRY BY SAMANTHA JANE ESPLEY-BOUDREAU Department of Mining Engineering taurentian University Sudbury, Ontario Febniary 1999 A thesis aibmitted to the Faculty of Graduate Studia in partial niifilirnent of the requirements for the degrec of Master of Applied Science Copyright O Sarnantha Juic Espley-Boudreau, 1999
2 National Library Acquisitions and Bibliographie Services Bibliithèque natiorrale du Canada Acquisitions et services bibliographiques 395 Wellington Street 395. me Wdlirigl#i OttsrwaON K1AW ôüawaon K1AW Canada CMade The author has granted a nonexclusive licence allowing the National Library of Canada to reproduce, loan, distrriiute or sell copies of this thesis in microform, paper or electronic formats. The author retains ownership of the copyright in this thesis. Neither the thesis nor substantial extracts fiom it may be printed or otherwise reproduced without the author's permission. L'auteur a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, distriiuer ou vendre des copies de cette thèse sous la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni la thèse ni des extraits substantiels de celie-ci ne doivent être imprimés ou autrement reproduits sans son autorisation.
3 DEDICATION This thesis is dedicated to the specid people in my Me- Fdy, to my parents, Gecxge and Beryi, for guilelessly pmviding those high-standatd benchmarks as life's objebivcs, for tbek unfaitering love and for their Uiiaest in my demic end personai j~ucney~ SaMdly, to my mother- and Father-hlaw, Roger and Solange, for th& never-ediq supply of love d assistance. Thirdly, to my brotha and sister, John and Belinda, for the constant guidance of their "lil* sister" and for paving the way. Fourthly, to my brothas and sistein-law, Pierre, Michel, Tanya and Céline, fbr their interest and encouragement over the years. Fifthly, to my adopted Wly, Uncle Les, Auntie Norrie, M e and Viv, for those many summers of fossil- hunting and geological expeditions, which set my heart in love with minhg and the beauty of the Near-North. Finally, and most importantly, to my own little fàmily; namely, my husband Marc and our four children Amy, Eric, Katnne and Miranda Thanks for being there for me throughout this achievement. encouragement to persevere with ali of life's challenges. Thank you for your love and support, and for the This thesis is also dedicated to my Gran, Alice Scaife, and in special loving rnemocy to my other wonderfùl grandparents: John Sde, Ethel Lawson-Espley and John Espky - if only life wasn't so short and the world so big.
4 The author would like to thank the management opinco Limited, Ontario Division, for the hancial support ad oppoctunity to pursue rock mechania meerch and higher edudon. PÛrticular thanks to the manager of Mines Research, Dr. Greg Baiden, Cor his guidance d support in this thesis. Thanks also to Mike Sylvestre, INCO's Manager of Technid & ûenaal Engineering, for pmviding the irnpenu ht pursuing additionai cducation. Appreciation is extendeci to other INCO managerial persorne1 for theii support of the various underground triais: John Kdly, Joe M g, Jon Giil and Fergus Kerr- Special thanks to INCO engineers, opedonal supdsors, technologists and miners for their input and assistance with research and testing John Galbraith, Robert Barclay, Chris Langill% Robert Tan, Denis Thibodeau, Parn Paradis-Sokoloski, Denis O'Donnell, Dunn Harding, Trevor Courchesne, f i Willan, Mark Ashcroft, Jon Treen, Brian Keen, Mike Leblanc, Wayne Lidkea, Andy Besserer, Mike Mkcioli, Mike VanderIiooft, George Dariii Chudc Berger, Brian Buss, Gilles Quesnel, Glenn Elliott, Tom Flynn, Len Van Eyk Don Gison, Eric Loney, Steve Townend, Leo Vienneau, Gary Smith, G ~ M Eady, Dan Fortin, Bruce Goard, Mike McFarland, Brian Abrahams and Teny VanKempen Appreciation is extended to NO'S Research Miners: René Fournier, Roy Cousins, Nelson Collin, Hugh Beck and Chico Vileneuve. Input fkom other XNCO specialty groups is gratefùlly acknowledged: Rick Riengeutte, Phil Salo, Teny Turmtte, Dave Maskery, Don Stewart and Damian D' Aquiar. Thanks are also given to the Mines Research Simulation Teaxm, for assistance with this thesis: Gaston Berthelot, John Galbraith Rdph Lam& Neil Runciman, Terry Villeneuve and Hulya Julie Yazici. Thanks also to Jason Villeneuve, who aided in compiling the data The author extends extreme gratitude and thanks to Ken Zeitt, a good eend and colleague at INCO, for al1 his hard wo* dedication, and input to the sprayon liner testing program and, without whom, this thesis would not have been possible. The author wishes to express paxticular îhanks to Dr. Peta Kaiser and Dr. McCreaîh of Laurentian University for theu excellent supe~kion, guidance and advice for this thesis document and for their contributions to the thin sprayon liner -ch at INCO.
5 In addition, Dr. James Archibald and Pets Lausch of Queen's Univedy are gratefùlly acknowledged for theu consultations and guidance fegarding thin liner support applications and for their collaborative efforts with technical paper publications. Appreciation is gnrtetiilly acknowledged to the following individuals, for their support and contributions to thin liner re~egtch: Charles Graham of CAMlRO, Dr. Graham Swan, M y Hill, Alex Henderson and Chris Pritchard of Falconbridge Ltd., Mark Diederichs and Dr. Derek Martin of the Geomechanics Research Centre, Ken Sutheriand of Placer-Dome Canada Ltd, Dr- Robert Mercer of ESG Canada and Dwg MoJn'son of Golder Assaciates. Thanks are also given to the many researchers, assistants and coilsultants involved with the N O Reseacch program: Jay Aglawe, Luigi Cotesta, Andy Charsley, Mike Stachmal and Sean Maloney of the Geomechanics Research Centrdiaurentian University, Dr. Don Trotter, Lionel Rudd and Dr. Julian Partyka of Lawentian Universityt Derek Erickson of Agra Earth & Environmentai, Chris Preston of Dyno-Nobel Explosives Inc, and Chris Kelly of ICI-Canada. Additional gratitude is extended to the material suppliers and thin liner application experts, for their valuable input to the research program at INCO, and theia cuntinuing efforts to implement liner support into the mining industry: Thomas Corbett of Engineered Coatings Ltd., Kendall Carey of Carey-Fawcetî Ltd., Man Peach and Clive Manden of Urylon Plastics, Jeff Jarboe of Futura Coatings, Teny Wiseman and Nancy Darling of ICI-Devoe, Mike Rispin, Brad Knight and Brian O'Heam of Master Buiiders, Mark McGoey and Neri Fratin of Alexander-Centre Industries, Marc Lamothe of Stewart Mining Pducts, Mike Mooney and Orin Devries of NORCAT, as well as Patrick Diebel, Ailan Ibbitson and Paul Sulman. Dr. Nick Vagenas oflumat is acknowledged for guidance on process simulation. Findy, the author wishes to aflh particular thanks to a specid colleague, Dr. Dwayne Tannant of the University of Alberta (formally at Laurentian University), for excellent work in laboratory testing and underground trials with spray-on liners. Specific thanks are given for the extensive contributions to thïs thesis: large!-scale pull-tests, adhesion tests, capacity detenninations and support mechanisms. Dr. Tannant's research and report documents provide much of the technical data for this thesis. Additional data interpretaîion for support design with thin liners was provided by Dr. Kaiser, with much appreciation fiom the author.
6 The objective ofthis thesis project is to investigate thin Coafings and sprayon liner pducts for use as ground support in the hardrock mining environment. The initial research work was underaken by the Mining Ihdustry Research -on of Canada (MIROC) in the late 1980's. The MTROC research work was published and released to the indu* sponsors &er each phase of investigation An enormous amount of chernical testing was completed by MIROC to provide the mining indusüy with a prototype sprayon coating, ~ine!guard~. MineguarP is an innovative, polyurethane-based, spray-on rock lining material that is intended primarily for use in underground hard rock mines and for other geotechnicai sites in order to provide rapidly-deployable area support coverage. A series of laboratory and insitu mine assessrnent trials have been undertaken through MIROC and INCO's Mines Research Department to determine support and other phy sical response capabilities of MineguardTM for various mi ning and geotechnical applications. The majonty of the tesearch within this thesis is based on testing with the MineguardTW coating, althougii it is clear that other new products will likely also prove to be viable materials for support of rock Some of these new coatings are the Futura Rockguard polyurethane coating, FOSROC's TekFIex, Master Builder's new polymer cernent blend materiais, and ITW Foarnseal's polyurea material- This thesis presents a review of practical considerations con-ng spray-on liners, as well as the results of several field case histories that illustrate various mining applications of this innovative support technique. This recent research is summarized within the following aspects of thin spray-on coatings: Technid Considemtions: P Materiai Properties P Support MecMsms / Failwe Modes Liner Capacities
7 0 Operationd Considerations: > Economic & Productivity Analysis Health, Safkty & Environmentd Concems Application Procedures & Prosoor,Is 0 Support Considerations: > Appropriate Uses & Practical Guidelines From a technical vicwpoht, the research involved investigation of the material properties and sippon mechanism of thin sprayon liners From thos wok the ideal material pmperties for ground support effiveness have been proposed. A generaiized cornparison of the support mechanisms has ken made for: (a) thin spray-on shotcmte and (c) bolts and saeen Using this infiormation, a lins capacity and a design guideline are proposed. The operational wnsiderations involve issues relating to the productivity and economic &ors as weli as the hdth, safi and environmental conads for underground mining and consideration of the flamm~bility of polyurethane materials. Baseci on the technical issues and operational considerations, the applications and limitations of spray-on Liners have ban tecommended. The implementation rewmrnendations are practical solutions relaîive to the mrrent rnining processes at INCO, with a vision of niture applications to improve ail aspects of hardrock mining. In particular, the use of sprayon liners for immediate support, with Iow materials handling, offi considerable merit for such applications as short-tm ground support to spd up a conventional development ~ ~OC~SS~ In addition, other practicd construction applications have been highlighted, for improvements to the mining operations in surface plants and within the underground environment Overali, the underlying finding within this research work is the in& understanding of how spray-on castings can be used to improve the mining environment and mining pmasses.
8 The motive for the mearch is the rtrong conviction that sprayon liners have the potadol to rmlutionize the minhg industry. This can k realind by: inmeashg the support cyde efficiency, increasing developm mes and pdudivity, cornpressing mining tirnes to hease revenue generatioc improvhg safety wùh reduœd support installation injuries, improving mining, müling, mlting and renning operations with a range of applications, such as ventilation barricades, conveyor bek maintenance, rainisebore hole ad borehole support, and as a consmiciion materiai for painting and coating steel and wood structures. Spray-on support also allows for the realization of automation visions for hardrock Mning whereby a liner is used as sole support in Fdst-development headings-
9 TABLE OF CONTENTS 1 INTRODUCTION 13 MIROCRc3curcti-PHASE Part 1: Flammability Tcstuig : U-Tiials Trial #1- Fatconbridge's Kidd Creek Mine T i MlRûCTnal#1 Rcsults TM#2-iNCOCoggerCIiffNorthhdkSudkny MIROC Trial #2 Resulis MIROC Trial #3 Results SirmrriaryofUndefgmdTiials SumniaryofMIROC Phase 2Testing 1.1 MIROC --PHASE 4: LS Part 1: Laboratoiy Pull-T&g Mis of Humidity Testing oa Conaete Shbs ResuitsofHuniidityTestingwithRodcSubstraia Sumniary of Laborato~ Pull-T&g Parr 2: H~midity Mitipihg Techniques Surbœ Heatiag Experimeniaticm Chemid Variation Experimaiiaiion Preliminary Red& ofhumidity Mitigathg Testing Overall Pull-TestUigResults: Sumniary of MIROC Phase 4 Testing: MIROCRcrulich-PHASE* Undergroimd Trial at INCO's Capper Cliff North Mine: MIROC P k 3 Results
10 2 PRODUCTNY & ECONOMIC ASPECTS LI htended Appliatiocu alsprry-ao Support 2.2 Ecobomic & Pdudhity Rnb'oarle for Utking r Spray+m Support Syrtcm Groimd Supn Costs & Installation Rates 2.22 ProduciMtyEstiaiatesAssociatedwithGmimdS~ DevelopmentRmss RodudiaaRocess Cut-and-FLU Mining Applications 2.3 Ecoaomic & Productmty Improvements for Ritun Automaîed Mina Graund Support Systems in Automateci Mine Envirorimaris 3 UNDERGROUND TRIALS 3.2 Noimda hc, Bousquet Mint Triai 3.3 Faiwnbn'dge Ub, Kidd Cm& Minc 3.8 INCO Ijmitai - Mine Triais Trial #l: Lmer Cdem Mine, 20-Slot, Top Si Trial m- Lowef Caleman Mine, l!mlot, Top Siil
11 3.8.3 TrialrY3: Lrrwer~Miae,#19~BoaMnSdl TrialW4- ~~Miae,3150RampInterseccian Trial#S: Lmwer~~3370~21&22T0pSills Trial #6: UÇCiwdy East Mie Main Ramp Triala CreanHillMiac,3800LevelGaragc Trial db: Cogpa ClinSouth Mine, 2520 VRM Tap Sill Triai= CoQQaClinNorthMiat, 1 070W Trial#lO:McCreedyEastMioe,153OreBody Field Trial #1- Cut ü FieldTrid#2-CU# ~ ~ û i t B o d y ûther INCO Ap9üdons for conannio Cdusioas of tbt Underggd Triais 4 HEALTH, SAFETY & ENVlRONMENTAL ISSUES 4.2 fieaith, Safii & Envimamentai IsJua 43 Control of Airborne Contamioaats Undergrornrd Tes&ing of Airborne ïkoqmaîes hcyamk Monitoring at Kidd C& Mine, T i Ontario Air Quality Testing at -ClinNorth Mine, July IsDcyanate Monitaring at Copper Cliff Noch Mine, Apil Air Quality Monitoring at tbe Sudbury NeutMo Observatory. Janar~ Air Qriality MonaOring at INCO's Laver Coleman Mine, Air Quality Monitoring at INCO's Lower ~okmm bfk 19SloS Aïr Qiiality Monitoring at INCO's Lwer Colerrrui Mine, 3150 Ra* Air Wty Monitoring at bwer Coleman Mine 3370 kd, Ibfardi 19% Air Qrrality Monitoring, McCneedy East Mine. Hiurlagc Ramp, Jw 19% Air Quality Monitoring at Crean HiIl Mine Decemkr SudbrPy Neuuino Observaiory Wall Sealui& Much Air- Monitoring at INCO's CogPerc~~ Muie, AirQualityUonitoringatMcCreedyEastMine,1~ Air Quality Monitoruig at Jundioa Mine, Australia LabTestingoftheWaterantairs1995
12 6 SUPPORT TESTING FOR MATE= PROPERTIES ai LaqEscdeRiU-TestResuIts Scrieen Pull-Test Pull-TestW t s Shotaete RiIl-Tests Everbond Pull-Tests Rodrguard RiIl-Tests 6.4 Conclusions on the Matcrial T h g
13 7 SUPPORT CONSIDERATIONS 7.6 Empiriczl Design Sup~ofi Design Qiaris for Estiaiating the No Support Limit SupgortPresureEstiniates 7.8 Design Guideünes 7.8. I Lunitatiolls Wedge-ConmUed Faure - Nowable Spans Sms ontrolied Faïiurc - Allowable Spans
14 9 REFERENCES
15 TABLE OF FIGURES;. i F 1. Can~gurcrdgurcrdm ofpru rat rpprrdirr [Arrciiibaid rlrlrl Fi' 2. &fidp&& urddùüian andprlkbqg amjgurdrgurdran [Arahib& 19u...rL Figwe 3. Pe-dpfaîe id- dpru"ng amt&mû*on [Aricliibolrl ' i F 4. Miiing namm vein Tm* lp97j., Fi- 5. Mnmg 153 OR, dops with &d b d Pm. 1997J Fi- 6. Mining M e fw namnv win Figrve 7. lh&.îïvitybwrdr fwncolimiled(&a'dat. 19P8] Egwe 8. Remo~eco~f of equipner~m an mdetgmwd stdaam Figrtrie 9. RemoleemûaI of u m h g m a d e q u i ~ ~ cmîmf mm.-....,., Figure IO. pxes t i using ~ waonwntid nrining m e M. 70 Figure 1 1. ihelopment qck. pxesr tirne4 mimg lek-rernok mhïng merhods Figwe IL Lac Mineral al's Bousqwt # I Mn e. MrregirardrrYc liner faïum by nppn g Egum 13. Map of the Sucibwy Bann wiih îhe location ofinc0 's Onm-O Division mi= Figure 14. Lower Cù&man Mme, p h WCO. Lower Colemun Mne Fipm I5. Te methdologv/rlow dim Figure 16 Plan of 2&%t with dre fixation ofthe Mnegtrarâ- liner 84 Figure 17. Sec!icnon of 20-dot top silk &matic of &sûhg arrangement Figure 18 ResuIts of iest # 1-1CfmeguardCM liner without rockbdk Figwe 19. Res11Itrofiest#2-Minegu47d'iwlinerwithout~1~ Figure 20. Top sifl sup~edmineguurd- and bolfi - be fw the p-e<lr &lad Egrve 21. Mineguardrru and bol& - a* the pjhear bht with liitle cdditianplfailure F i, 22 M o n of ùrsawnentatian in 20 s/d fiel plan) Figure 23. Esasive slabbing and spaiiing in the lower w& with no support Fipm 24. Damuged utailr wirh boll and m en suppr; figure 25. Plan of hwer Coleman Mine. blasthole top sills; 19 dot and 20 dot:... % Figure 26 Lucntion of ùisarunentahahan in 19 sfot test 9îe -plon sxtion Figure sloltopsill~~p~edin~baakandwalkwi~M~1egu~Pndbdri~ Figure 28 Inlact &il1 hole collmd tbugh MneguartF fine r. Lower Colenian Mine Figure 29. Plan of Luwer Coleman Mine. 19 slol boitom si14 /don of Mn9pirfl Fi, Appli~tion ofminegrad- in the lower waff of a siif kacang 104 F i, 31. MinegtcardiM applied ~ rïuwer l Coleman Mine.... IQ8 Figure 32 I&n&$~an~on of W&g Mes h g h îhe Mneguard'" liner Figure 33. EaaIy Iüswnitnitb& nxhmis joiintrng with Mirquani- coanirg Fi' 34. RippedWmegucmi- on Ihe wafl of the 22 masrd Fi- 35. Slnoding ofth amting II2 Fi- 36 Foaming of lso-~~*ah ma&nr al 1W
16 figrue 37. Ap~~cutîan o f M ï w overbdtsandscmen,..., Figrure 38 NCO 's ~ pa&iaziicm equipnenr.., o....,. ~.,.,.,. 114 Fgum 39. Appricatr'wr ofm-#wn a. buck&fiann..an FSgrve 4Q Rail -km ofmuicguadry mat& to dk..., Figutv41. MneguLgdCbl~KdovwbokPnd~arashdcnc&rr-.,.., , 117 fi-42 mmwiîhamiaxaîing Fgwv 43. MÙtenenaf Amcai-ng and qpücdion 00Jllpa*i9a31: shdorlc vs Mi Fi- 44. Caa companoan of shdawk wrsus Mihepmi fw W~l~lop sill su* Fi' 45. MinepanP appli~d2~œt (r0 CC hîh Min e W. Wtop siu dbd& in the k L 7306stope, pe.pe Fîsrup 41. Sublewf mw minulg at Copper G?irNi Mine: Figure 48 Pfm ofm&ei& Etau Mi ne. 153 OrW hl: F~grve 49. Speee-bfack can/gurengurenon (a&r Touianî. 1998) Fi~grve 50. Minegrrad- applied to ihe fvst the test mm& ofaiaial # 1...~...~~~~~..~~~~~~ Figure 51. Plcm aid sedrdrons ofhard # I stop Figure 52 Sbychvai mqvpùig aial # I Figure 53. Comrgenœ &wûracaf. bmk (dsplcl~emenr) meanuiements Figure 54. PuII-hî dds, Egwe 55. Ownx~l*ng~r&re Fi- 56 Ided d3k fi Pulleddsk Figure 58 An emmtple O fjwot adhesian wiîh the Minegirad- fine r.., Figue 59. 3m.s slobbing in the back and walls of rire namnv vein stopes; 153 OB Figwe 60. Two test m d s in cut #3. &iai # Figure 61. Failofgnotmd in md#2. ûw #2: Figure 62 Rockguard maticoqnng on a dwefopment ch-fffaae: Figure 63. Remoteconbol appdicahcahan ofmmgrrard" at the 175 OB Figiue 64. Wgun rno~hdon the a m figure 65. Am mdgun remde cvnbiols Figure 66. Consrruciion of a barnamcade UMg Fabrend and welde&wire d: Figure 67. App fiuztion of plyuma mu&rial in the t a h a! INCO 's CIizr&ffe MI[ FTgive 68. Application eqdpnent& p w a materiak...~~...~~~~.~..~~~...~.~~~.~~~ 144 figure 69. NonedIuIbr vem f~iedpm"~~mte/pdyic~a cwtings Figure 70. Dnrm laberc; as supplied un& WHWSpi&fines Figure 71. MÇ4 lype mash, wiîh pan pan^^ mi faed f i the &IS Figive 72 SC&4: ser/kontaurtd brraphing qpmûm Epte 73. MDllesbngdururg 19sloîM~ardClWopPicntian
17 ' i Egwe 74. MDI~riesullrdwp1~~rÊstrmcrs~aMnegv~~msile fi- 75.-plai 153 badge namp...* Rigurre 76 -plor of Orar Hfl MW higrrrppc#umdi m~~l~&wng Fi- 77. OwrJproy cduurg Mnegvadni qpir'.i=dion wn uuaz poar Wbili&.-.ry Figure 78. Water puy nanile (or acomrr#) on the puy haat figure 79. S&herrmbcofhekstaanrl, withl~~b~aasof~ill~~l~~torsdwriruavlrrins Figurre 8îl View bkhg ksi& Phc qmy auuwfwkqmae &torvlg Figure 81. Air;f]ow wfm-ty m~urement~ bem td.on in îk îunml.., Fi- 82. Aoe&km d an g-/raw oqt...oqt.oqt... Fi- 83. ( Z r )...-- r)r) Figrcrie 84. Acetyhe &LW& on s&?p stod Figure 85.,Feld ngirishedlirp (inrtsir)...r) Figure 86 Torrir on ore & M irregire F 87. &I/krhng~ishedfim(indan!) Figure 88. Pnnmyfindrdraris of mppporl system ~C0eat.h & Kinkr Figure 89. I&nb~catian of riock satrclurre Figure 90. WeUed rpak siufke Figvre 91. Large-scafe ksî equipment~ematïc [Tarut ant Puîîem of cruiaiete b l d wdfw îhe testpaneis [Tannant ~i- 93. ~eclcmgtr~p~ QWICX~~ b l h... 2m figve 94. ffiztnganai anrmere bf&... 2Od Figure 95. LoaddispI~~ciements for wrious xmen typr /Tannan& Fi' %. ~ ~ a u? m ecu~esj6r n f #6gaugie caaeen an mdan8r(i ar bkxk Fi- 97. LooddiJp/~aement avyes* #6guuge men on h q m l bf& Figure 98. Large-de -hg Figure 99. Un&rsi& of testpanef # Fi Talpedsucf- ofle heragonaf -te bi&: Figure 101. Lnaddisplement resufts Jiu A4ineguîm-P over h ~onai bfocks Figure 102 Load-displement eumsjôr liner inif Iing wih rectangrr for b focks Fgure 103. ioddisplacement d t s fwminegrc(pdch and screen Fi LoadilisplllcemntcwwsforMineguCpdTM(2nvn/ Figure 1 OS- arcles fw rhrck rylp Iicatim of Mneguardrrw Fgure 106. nuakmmqpmpiiner Fgure 107. ïhin Mine- liner Figw-e 108 Thsile mpîwe of rire liner Figure 109. Joint infiiaahaahon of tk lkr figure II îi MinegumP and saeen testing: men wire snupp d
18 figure 111. T'-ngjhme adaovrrote base ~~ed~pdl-~csn~ng OfblockpneIs Figrcne 1 IL Slhdaicte spaying onlo kstpaief* Clrgc-ml& pru figure 113. Vtcynrsw m~dd&mfe p i 199v figum 114. Puü~ofmtshd~te ,...,, Figure 115. BackoflllGJjiJ.lidarr~tpmei F i w 116 Eiwiy lardtrisrmy~sliolcrretepairels~~ 1991].., Figure PtrU~anjbrreshalcffLe Figicne 118. Ckkedjîbm A& pd F m 119.-mw M i and- ~011101& 1997J Figure 120. Lolexponel fw &&hg.-...ar. 225 Flgruie 121. fœkd blwkr Figure 122 ~ t t x n e J w l d k r ~ & Ewrboui4. (Tpltlyllf , Figure 123. cunes fw th& MnegrrmF and Idex Figrcne 124- cmes for R ~prrneis 1#5 to # 10) f T ' 1998] Figure 125. Acmesion M n, anangement [T Figure f 26, Unai& ted arnngenienl fz Crcaesm lestr fstherkm Figure 121, &helllpblllpbc of a *el &IUy uspd to lest admion [Zhthwhd 19iW] on Fligure 128. Adksk siriengh disfi lalex mqteriai /ïii. 199u Figure 129. F~gure 130. Sqpd of a wî&e wwiiii... CLVH~S fw Rockgvd~o~ lests (Tanntmf bok Figure 131. silpporr of a we&e wiîh a sprqydn liner Figure 132 Polentïd fàiitm mds of* menrbrme su- navurtl Fi Liner ocihesiim copocrcopocrty: to supptt a weli&flned we&e damg 247 apcm~fined we&e Fiigure 134. Lufer membra~e qnxïiy: to sup+ Figure 135. Liml e~uilib- cmcbysisj6r thin liners d/kx ùi-) [Tomcrrir. 199i7, Figure 136 Wedgie 250 F~gure 137. Dimensions of &bon&d Iiner and 2.51 Figure 138- &h&d liner wiîh weee &&drdron (izctian) fi' 139. Locoa'~lt~ofmedranetm*mand~~/nive~rireprll~~(~~~mf 1998] ,. 254 F i, 140. Locab'on ofnrcy-w liner nipïms fo~p~l4 [T'ad. 199g Fgum 141. Loaddisip(axment curie for paitel 4 flood hp & 256 Figwe 142 Auidiing-bld shtr test [ArdribuZ4 1992J Fgum 143. Sbiess4iwn fdng Jystem figrue 144 Mémbrsre and kani mabêisfw czsess-ng Iimr S Y O f m~ d... dgrorad 264 Figure 145. Cimula wmw padkl-dl mpport Figrve 146. F m &qgmmma Ubuled l d m a able figure 147. Mcapaiity ad su/ilporicrble ofbkd nidb fw rdijaibured I d
19 Figure 148. Point-iOOdJbnr ( d m Fiw 149. cadswppartabde volume ofd* apornt-iwd Figiure 1 SQ Poiht-Cocrd&dtfburcd ~ p C d c. r..., Figue 1 SI. Beam ordniembttvu W Egure 152 Load esiundione Woiu beam tlikbwsws, Figure 153. Nh~~lppi lîmit* rvprvpcdnco tdmss dtianr ,., fi tfm dcsign kxh+zs#u thin lutors Fgwv 155. Ra& bmt hk in hi- mmrning dlwonmbnt figue 156-3mss-co- in an unsuppîed ore pas at NCO fi Po~t-p~llPi.otlNCO'sA&Cke~&E4aMuie,Main~ -. UUUUU- 290 akmicrds= Fi' 1581 ~ofpdyuiroa Figiue 159. Sp'cry grar 295 F i p 160. RemoteemthIIed dmtmte appiicaîïan epipment
20 TABLE OF TABLES: Tpble 1. AclI-kst msui;rse#m amhgmmd rrzolsat~c0 IIm~ted~~r Table 2 Aihsim and end vqyuig iiunu&.-.,..ay.ay Tabk 3. S v m r m q y o f ~ ~ d ~ e ~ ~ - n g / n u n i ~ e s t m d ~ ~ - & Tabk 4. Maienaiena/ values* vqying humr'cr!y lewls md subshmk mderiols riolsriolsriols Table 5. Ac#&w sïnwgtk wiih M i? vaiapi~fi humùb'îy lark Table 6 Mclterialpropeinines~ - M W-M- HH453 mm2au /Mèmr, Table 7. Pull-fat dlsm MIROC Ph- 3: NCO Tria&6eriser Table & Fn'cîionfktw (Y) re~llils& rïvway Tobie 9. Materiai agingaidahemicalipssrcpiae chrde&zcsofv ~abk la of.ppwr m-cierclaol~s f~dbdder d.. ~992~. 49 Table 11. 5kmnmy of su* cmsi&r~a-~l~~ aîiivc0 Limmrted (1998 dam)...,., Table IL hbdk pnedirctim inlemrpîïons and asmciated axî impocrs Table 13. Srnulaiion shrdy tu mm- &If-dm sup* ws her suppwr: Table 14. CompcpzFoYl of cœtwntimd and telemmole tkwlopnent~ Table 15. beîwen ~b~ wmus tefeminiing &elopment: Table 16 Clvrenî &Nelopnentprxlesr wmus re&gn /%fafoney & Kaiser. 1997J Table 17. Summny of testr-ng in 20 slol. hwer Coleman Mine meye Table 18 Air quafiiy mollfollftwrwrng at CC N d Mine fleurwwd Table 19. Air quali& monitorurg &&.y Nkutrïno Obsm atory [BMZ /993] Table 20. MDI monitononng McOiee&EaaMne. hhge rmp mengevlte Table 21. MD1 manifononng tv-sul'fir Giem fil1 Mine (Riengeutt e Table 22 PartrartrcuIaîe duld samphg ut CC South Mine U Table23. Airqualiîylestre~uftsatJ~dr~anMine WA.[FinneL d Table 24. &mminy of ventilatïon~ow condtions [Arcfribdd andltnisch Table 25. T& gasesfim poljweihane mdpeyww>d /Mwdve Table 26. Nonuzllular Mineguard'nc combut~bn mlts [ORTECH Table 27. Gdluhr f0(111149mnegircrrdrrr cwnbusttiildrm riesuf~s [ORïECfl 1997'... 1% Table 28 hpimm &ber fin combwtr-an tvsulf~[orïech; Table 29. hpertrrtres of amcm& blocks ued fw test pmek /Tannm& Table30. Sicmm~qyof'll~on blockswith #dgaugesareen[tannant ~~~.~~.~~~~~~~ 207 Table 31. Pirll-test re~ul~sfi #6gairge =en Table 32 Pirll-testresul~s~ MnegvardCM appfied e n ped foad capaaïïes flo~cmt Q8. fïànnant 199fl 210 Table 33. Pull-~led riesiriisjsr MineguanV on blackr /ïànnant Table 34. Resulisfw puli4ed.r an Minegue in/illhg~is [Tmmt Table 35. Lc;rad-ciEsploc;emenb fw vtmclll~ rhrcknesaes ofmineguardlm [Tmuumi, Table 36 hxddspkemnb fwmirregu# [Tiwmant. 1997"
21 Table 37. ~ j Z 5 r. i W œui- radpcaek~imnan~ 1997J Table 3 B. PJI-&s! re~lllks* -te praek f l ' 199fI.,.,...., Table 39. Puif-&s!msukr~R~a b&d panmatg I998J... J Table 4Q Thsile lestr an 19B], Table 41. Smmmy of MuwgvprdcaI a& W....r Table 42 AMan test -la*- floluplt; J9BJ Tdle 43. Caparty edmdefipetak lard ut panel Table 44 Ccrpacity knad &vps in panel Table 45. Btimaied loadqxx5tie.s based an &vgdepulf-îeia dara Table 46 Muieguordrrv hdemy&g cqpmcqpmfy... bwd an the he& pull-&sî &a Table 47. MirwguanP capacqpicrty baaed an MIROC solidplare puü-mts Table 48. A&&ve s&engîh ojmimegrranp wiîh mck subsîmk [Arahrbaîd Table 49. Gtpaciîy pmdai. tests Toble 50. Minepar fl rdiear ~aengh esîimated by puidring ksts. 261 Table 51. Siunmmy of Minepurd Wgn dues Table52 Nosupporlümiil~ponr(inm) fwarrmge ofqandeszvdues Table 53. &pporîpewms (in Wu)* rvprrvprazi NCO riwkmcrirs condtim Table 54. BeneJts of a Uirn mpplckaelling sg~y-on liner Table 55. &t-up times corrielded to tna&rid quolig Table 56 hperhés of Minegucud-: cwnpmnts and cved coaîïng [ilman, 024WJ Table 57. I&d q w m liner pp rtirties md chanxseridtics
22 INTRODUCTION Spray-on liners were initiaiiy invdgaîed for use with the mining indusûy thmugh a cooperative riésearch organization called Industry Research OrganiEation of Canada). This agency was compmcd of memh fiom in-, acacknih and govemment. MIROC began materials research for the rnining industry in the late 1980's as an addendum research group to the otha sista otpnidons: HDRK (Harm which was f b on equipment development) and MRD (Mining -ch Dbctom&, which was focused on rock mechanics and rnicroseismic research). Wiihin MIROC, the process of installing ground support to provide stability and de access to workers was recognïd as being extrernely labour intensive and time consuming The typical support system used at the tirne of initial research was similar to current practices of rock bolts and screen. The advent of shotcreie technology was also emerging in the late 19803, and =OC also recognized the shotcraing process as king resounv intensive, for transport of materials to underground headings and for application. As an alternative to bolting md screening and to shotaeâing, MIROC began to investigate the possibility of using a rapid-setting çpray-on liner, with very thin applications, to provide ground support. Sevd types of coating materials were investigated through MIROC and Queen's University Mining Engineering Department in Kingston, Ontario [khibald, however the most promising produd was a polyurethane material, called ~ineguard~. The original MineguardN material is manufàctured by a Canadian company called Urylon Plastics Inc., which is located in Guelph, Ontario. Following rigorous research and chernical alterations, the final hdineguardtm product (known as MIROC MïneguafdTM) was created and has been available for industry use since More receritly, altemative rnanufacturers and sprayon products have emaged into the market place for consideration by the d g operators. These alternative products offer an array of support mechanisms and functionality, analogous to the wide seledon of rock bolts available to the mining industry, for a range of support applications.
23 The MineguanP development has undergone five distinct phases of -ch assesrnent within MIROC. As each phase pmgmsed, new and signifiant bene& wae demonstrated for rnining applications, other than for support. which may provide substmtkd cost savings and fitvourabie operaiional implications to mine operaton. The initial MIROC work ha0 beai since supplemented with teshg by INCO's MUKs Research Depariment in Copper Clif& Ontario. SpeciGcally, INCO's fe~eacch pup ha9 conducted underground trials and laboratory testing of spray-on liner products since The INCO research has been conducteci in consuhation with Queen's UNversity, CAMIRO, and with sprayon liner manufachirers and application experts- Actual contracts and COordiied pmjects were also set UP by INCO with the Geomechanics Resean:h Centre Iocated at Lawentian University in Sudbury, Ontario. The 8-year research phase at INCO has ailrninated with this thesis, whîch presents a review of practical considerations conceniing MineguarP use. As well, the results of laboratory testhg and seved field case histories are summarizeâ, to illustrate various mini ng applications of this innovative support technique. The underlying objective of the research on spray-on liners was to introduœ an innovative and effdve ground support produa for the purpose of revolutionizing the mining industry support methodology. This is achievable by effedively (a) reducing the time necessary for minimizing the rock pre-conditioning requirements, (c) decreasing the material handling and labour requirements, while (d) promoting a high degree of autornated handling capability. Overall, the thin liner products are intended to compete with existing support systems, f?om thin shotaete liners to botts and screening. Eariier research work conducted by Birch  and Mercer [lm investigated the h4ineguardtm material to conceptualize, develop, test and refine the produd into a means to dely and effectively supporting a roclcmass.
24 The r~search work by Maca [lm] d e d the total load-canying apacity of the Liner in response to deformation, to gain a better understandimg of the support mechanisms. His work also considered underground test mlts to the effdveness and p ddity of ushg MjneguardTM as a support produa Fdy, the reseamh compareci shotuek, msh and ~ineguard~ within four gfound support d o s. The earfest support mechanism theory was a p m differential supposition, calleci the Caisson Effi &ch was a<amined by Gyenge and Coates and lpter by Archibald and Baker . Thk theory hypothesised that an air-impermeable üna, sprayed ont0 the rockmass dace, could create s pressure imbalance as the rock mass degradeci and deflected into the excavation openkg- Very thin impermeable liners could therefore be seen as support products for a range of rock mass conditions, by utilizing thk Caisson E ffi The original formulation of ~ine~uardn was a result of the initial research and the pressure differential hypothesis, The initial laboraîory tests on bfineguardtm were completed by Birch and a dinement of the MjneguardTM formulation came about as a result of a second series of laboratory tests [Mer-]. The strength characteristics of two standard support systems, shotuete versus bolts and meen, were compand with M.ineguardm's capabilitia. The work by Merca 11992) suggests that NlineguardTM's support capacity is more than bolts and screen and less than shotcrete, 10.2 cm (4 inches) in thickness- The foilowing descriptions have been taken f?om Mercer , Birch [MU], Archibaid Cl99 11, and Archibald and Baker . A literature search was conducteci to identifi. possible materials that would provide an air-impermeable coating for rock, to mate the Caisson Effect for support. Three potential materials were sourced: 1. A two-part (min and dyst) sprayon polyurethane material 2. A solid thermoplastic powder which is applied using a flame-spraying methodology 3. A paint material, applied in a sptay-on fàshion
25 Witfi the base aitecion that the produt must be suitable for und- use, the three materials were Mer fe~earched to determine theu appbcabiiity for the minïng indusby. A set of ten criteria, as liste4 were ectahlished to rate each produd: 1. High m ile strength and elastic properties 2. Capable of formïng a oontinuous laya 3. Capable of adhering to dry, d ii, wet andor porous airfaces 4. Able to cure rapidly, even within variable humidity and temperature environments 5. Must utiiize readily available technology for application, with minimal need for traininghse 6. Cannot -te adverse pnicessing or metallurgical effects 7. Must be fireretardant 8. Must provide minimal worker exposure to chernical hazards beforddurins/after application 9. Must provide cos& benefits for competitiveness with current support systems 10. Must utilne versatile equipment for application over a range of excavation geometries. The candidate products were subjected to a series of four tests, to rate their applicability and practicality for use in the mining industry. The tests are sumrnarized as foliows: Each materiai was applied to rock sufice outcrops at the Queen's University Explosives Test Site, in Kingston, Ontario. Materiai spray properties were detennined and application evaluations were conducted. Adhesive strength tdng (ASTM D , 1983d) on suhces of rock specimens: granodiorite, granite and limestone. Application testing for cost estimates and application rates, based on apptied thicknesses and area average. Health, safety and environmental dety concem evaluations, based on transportation, application, and finai liner properties.
26 12.1 Summary of MIROC Pbue 1 Testing In cornparison with paint products and flame-spread materials, the Phase 1 testing concluded that the polyurethuie pmducî was supaior in physical tests, cos&, ad application rates The polyurethane membrane (UryIon ) was appüed using cornmanil prrrauurd rprayers that combined quai fluid volumes of the min and d yst chernicals. When mixed at the spray gun nonle, rapid chernical d o n polyurethane wating is created ocarrs ad, within seconds, a ta&-fiee, soüd When additional application testing was conducted on near horizontal and vertical rock fàces, the polyurethane material was observed to cure within seconds of application, with minimol mnoe or bleeding fiom the rock surfhs and with minimal overspray or rebound loss. In some cases, the polyurethane coating was applied to wet rock surfaces whereupon the ha exhibited a bubbly and foarny appearancce- This phenomenon is known to occur when the catalyzing agent cornes into contact with water, rwlting in the formation of &n dioxide gas bubbles which, in tum, become entrained in the liner. Further field trials were conducted to assess layer adhesion durability as well as mistance to seismic shock In these trials, the polyurethane wating was applied to near vertical rock fàces whereupon the membrane was then subjected to the effects of detonating one cartridge of commercial explosive at a depth approximately 0.5 m below the outmp su~aces and 0.5 m inside the membrane boundary. No separation of the polyurethane membrane was observed to take place from the rock dace, indicating that substantial adhesion bonding capability was maintaineci. Based on initial tests, the polywethane matenal: (a) demonstrateci ease of handiing, (b) was able to be applied in a thick, uniform coating at high application rates, (c) showed excellent gap coverage capabüities (up to 0.5 cm widths), (ci) evidenced sufficient elongation eapacity to deform readily under tension (between 545% strain without fàilure) and (e) generated the highest adhesion pull resistance capacity of al1 the materials tested.
27 However, the testing highlighted two areas of wncem: 1) the health, safi and environmentai hazard and 2) the technid aspect of mataial pfopeny Mon. Specifidly, the polywthane pcodua ansisu of an isocyanate as the atalyrt wïthin the -part system; this requires investigation for handling and application As weu, investigation to de<emiine the risks assocjafed with flammability of the polyurethant membrane is warranteci. From a material property concem, the pdyurnhsne pdua indiated a dramatic los in dhesion when applied to a darnp wfke This characteristic, whüe insiflcant for rnost applications in the manufàchiring indusiry, is a serious problem for the king industry whereby the underground environment is mostly aiways humid and wet. Despite these two signifiant drawbacks of using this polyurethane material in the underground environment, conceming the health & saféty and adhesion, a recommendation to proceed to a second phase of testing was made by Queen's University and accepted by MIROC. The MIROC second tesiing phase involved tùrther testing of the polywethane material (Urylon S), designated MineguarP, as follows: Part 1: flammability testing, to evaluate material flammability and the fire hazard potential of the polyurethane produa and variations thereof Part 2: underground trials of the -part polyurethane coating, with and without a pneumatically applied top-coating of vermiculite dust 13.1 Part 1: Fhnmability Testing It was recognized that standard polyurethane foams and solids will bum in the presence of open flame and will continue to do so upon removal of the flame source. Initial product redesign thexefore incorporateci the inclusion of fire retardant chernicals to provide flammability mistance.
28 Three Minegu.ardTM produd systems were tested for flammabidity within this phase of the MIROC research testing: 1. Mineguard??: the original formulation of ~ineguard~ as developed hm Phase 1, with the addition ofa fixe tetardhg chernical, Antiiblazem80 Fiame-Retardant. 2. Minemiardm3: the ~ineguard- fomulation plus a top coating of a pneumatidy applied aushed vermialite material. The vermiculite d n g is applied while the original polyurethane d g is curing ce- within 5 to 30 seconds). 3. MinWardm4: the h4ineguard'im3 system, plus an additional second arrfsce coating of a water-based dispersion of vermicuiite. This secondary coating cwld be sprayed over the original ~ineguard~ layer at any time, even after curing The emulsion d g intended as an additional fire retardant to be used where required. was The new, flame retardant version of the polyurethane materiai was designateci MineguardTMFR When sprayed ont0 cernent board or rock dabs and placed in con- with open flame at temperatures above 480 C, this maîerial will physically decompose but not burn. When removed fiom contact with a flarne source, burning is not sustained. The second variant form, MineguarP3 (or MineguardrnrFR+V) which has the vermiculite topcoating, was developed and found to be capable of resisting decomposition and buniing, even upon exposure to extreme open flame source temperatwes as high as 820 C. The level of flame resistance required for the underground environment is worth M e r investigation. The flammability testing of the Liners (Archibald, 199 1) involved subjection of the cud poiyurethane materiais to three test methodologies: 1. Smali-sale flame testing 2. Flame spread testing 3. Dynarnic t h d effects
29 Each test sœnario and the comsponding oonclusions are summarized hereunder The standard procedure developed by Undawritds Labodes of Canada (CANWLC- S102-M88) was olightly died in order that polyurrthanc muaial siamples (15 an x 15 cm) were subjected to three d'ierent heat sources: Radiant air heat gun (260 C) Bwisen gas bumer (480 C) Propane gas bumer (780 C). A standard distance of 5 cm, between the sample and heat source, was used and a total heatimg duration of 2 minutes was used per test. The samples were prepared with direct bonding to a backing materiai of either cement board or rock Some unbonded samples were also tested. During heat exposure, the time to perforation, the diameter of perforation and charred zones, and the flammability potenga1 of the material once the heat source was rernoved, were recorded for each specimen sample. Results of the flarne tests indicated that al1 sarnples subjected to low ternperatwe radiant air heat experienced only surfàce discoloration Under higher heat -sure, al1 bonded samples showed nonambustibility whereby the flame would extinguish once the heaî source was removed. The bonded samples also dernonstrateci substantial resistance to heaî induced degradation, as detennined fiom the time to penetration rates and the diameter of the charred zones. In cornparison, the unbonded flame-mistant mples that were exposed to higha temperatures (480 C to 780 C) also demoristnued no ability to sustain flame once the heat source was removed. Only the non firaresistant samples, unbonded (MïneguardTYl) sustained material buniing even &er the flame source was removed.
30 These tests followed the standard pdures developed by the Undecwriter's Laboratory of Canada (Le. CANNU=-S102-M88) for Surfàce Buming Charactcristic Guidelines of Building Materials Md Assemblies. This test rdects similar recornmendations that have ban developed for modincaîion of the ASTM ES4 Test Method- This test, dso known as the tunnel test, provida a flame sprd classification (FSC) ratuig for building mataiils Samples were mounteû on the roof of a tunnel chamber snd a flame source was uitroduced fkom one end of the chamber, under a constant air velocity of 1.2 mkc. A time period of 10 minutes was allowed to elapse prior to adyzing the flame spread on the samples. A flame spread chart is used to compare the results for various rnaterials, whereby the base case for red oak samples (6 mm in thickness) has a FSC of 100 and gypsum board has a FSC of 15. For cornparison, government legislation requires a FSC limit of 150 for materials used in residential construction and a FSC limit of 75 for building materials used in hospitals or other public institutions having timited egress. The four ~ineguard~ variations were tested giving FSC values that ranged fkom 220 (for MineguarP 1) to 43(for MineguarP3). The MineguarP2 (without vermiculite) exhibited FSC values as low as 4 1, with an average value of The two systerns of flame retardant MineguarP, i.e. with and without the venniculite topcoaîing, demonstrate signifiant flame resistance potential. 3. Dynamic Irn~act Tests: The polyurethane rnaterials were subjected to high temperature explosive shock waves within the Queen's University Explosive Test Site Facility. The test set up involved wrapping sheets of each individual test specimen within a 1.0 m3 airtight steel chamber, in which an explosive material was suspended and detonated.
31 For each polyurethane variation, three different explosive charges were utilized: 1. Magn~sooo(lsog) 2. Detasheet(75g) 3. Sulphide dust (150 g). None of the polywethane matends experienced damage or alteration fiom the tests. Foilowing each detonation, an analysis of the aehausted gases h m the blasting chamber indicated only the presence of decomposeci explosive gas products. Analysis of the flamrnability testing scenarios allowed for the conclusion that the three pdyurethane variations of Mineguardcw: 2, 3 and 4 effectively reduced the fire hazard associateci with using polyurethane materials underground. The recomrnendaîions fiom Mercer  were to utilize the MineguarP3 variation (using the Antibld80 fire retardant and a top coating of vermiculite dust). Further practicality issues and analysis of tire testing suggests that the MineguarP2 product is prefmed for undergruund use at INCO Lirnited. The work by Mercer LI9921 examine. the productivity potentia! and economic benefit of using the MineguarP pmdud to replace bolts and screen for ground support. However, the economics and productivity results were based on a single pass system In actual underground use, the -pas productivity as well as labour and materials. system is costly, in ternis of Additional work was çompleted by Queen's University (not published within the MXROC reports) indicating that the MineguarP3 variation has one significant drawback The problem is with the vermiculite layer when there is intense fire acting on the MineguarP. In this case, the vermiculite becornes very hot and actually acts as a cinder blanket, to prolong the fire. As such, the recomrnendation within INCO was to elirninate the venniculite dust layer and use the flameretatdant version, i-e, MineguarP2.
32 Due c achaustive queries on the flarnmaôility issue of polywehne membrenes, INCO a h undstook additionai testing to i d e and off-gases produced durhg vain of the polyurethane membrane to a flame source. Three underground testhg prognms were wnducted in 1991, as summarkd by Maca (1992). The first trial was Md at Fakonbndge's KIDD Creek Mine in T i Ontario, and the second two trials at INCO's Copper Cliff North Mine in Sudbury, Ontario. A number of expaimental aiteria were examined for each underground trial, as summarized: 1. Determine the application rate, the applied thickness, and the geriefal cost of the applied coating. 2. Evaluate the application of spray-on coatings in the underground environment 3. Conduct the air quaüty testing, to evaluate health and safkty concems for spraying polyurethanes in the mnfined underground headings, 4. Evaluate the ability of the eoating to infiltrate joints and fissures in the rock mass, and the ability to span gaps dong the rock mass sufice. 5. Evaluate the long-terni behaviour of the coating. 6. Evaluate the performance of the coating near the fâce of a development heading. 7. Evaluate the stmgth of the coating to estimate a support potential. Wiih respect to the health and dety a>ncans. air concentdon mmments of unreacted MD1 and reacted polymaized isocrsu\ates were made by the Ontario Mïnistry of Labour (Health & Safety Support Services Branch) during the trials. The measurrments were made directly at the spray sources and at various locations do- h m spraying using chemical impingement monitors and liquid chromatograp hic anal ysis of the reagemt solutions. Under the ment Canadian regulations for MDI, the tirne-weighted average occupational -sure concentration for MD1 may not exceed pprn (5 ppb) for an Qght hour &y and 40 hour work week The short-tenn exposure iiiit mot ex& 0.02 ppm (20 ppb).
33 Trial #1- Falconbridge'r Kidd Cnck Mior, I"immias As described by Archiiald and Merœr , the trial at Kidd C d Mine in Thmhs, Ontario was undertaken in The test site is descn'bed as an underground air- receiver chamber at the 2800 Levef (853 m). The dimensions of the excavation are 48.8 m by 7.9 m with a 3.0 m height. During the initia1 development of the chamber, bolts and screen were used as support. For the application, the screen was systematicaliy m ved while the back and waus were sprayed with ~ineguard'im2 with a thickness of 2.5 mm. For complete sealing of the chambr, the concrete k r was sprayed with the polyurethane. Due to the nature of the excavation, the venniculite was deemed unnecessary. For the triai, the site was ventilated a. a rate of 300 m3/min, with a resultant airtlow velocity of0.20 mls. The presence of dilatai m e s in the rockrnass permitteci testing of the gap infillhg capability of ~ineguard? In some areas, the gaps were too large for the initial coathg to seal the rockmass thus a second coating was required. In order to enhance the gapping ability of ~ineguard~, the material was sprayed with a srnall volume of water added to the mixture MIROC Trial #1 Rcsults The Kidd Creek Mine underground trial results, relative to the previously listed set of goals, are summarized as follows: 0 Application Rate = 1.23 to 1-63 m2/rnin Coating Thickness = 1.66 to 2.87 mm Application Cost = $18 to $3 1 /m2(s CAN 1992) Overspray CC 1% of the total weight sprayed Air Spray Site: MDI, TWAE < 4 ppb; TEA and polyisocyanaîes = negligible Trial #2 & #% INCO Copper Qiff North Mie, Sudbu y BegiMing in Febnary 1991, two underground trials were held at INCO's Copper CLiff North Mine, located in Copper CS6 Ontdo [Mmcer,
34 Relative to the test objectives previously denned in Triai #L, the second and third underground trials were primarily undertaken to address the round-by-round performance of Mineguardm in addition to the long-term behaviour of the liner. Specificaüy, the goals of the triais are outlined as foliows: 1. Confm air quali ty resul ts of Trial # Determine the adhesive strength of the coating. 3. Evaluate the application pnmss of M.ineguardfY3 with a vermiculite coating. 4. Evaluate the achievernent of consistent, thin lining applications. 5. Detennine the blast survivability of the liner. For the adhesive strength determination, a pull-testing experiment was &vised by Queen's University Mining Engineering Department wercer, The equipment for puil-testing the Liner was designed to masure the load resistance generated by the thin polyurethane Iining in response to king pulled away from the substrate surface [Archibald, The apparatus consists of a pulling yoke attacheci to a hydraulic ram, aii suspended with a tripod. A puil- plate, adhered to the substrate surface, is pulled upward using a hydraulic pump. W e measuring the pressure of resistance, the yield distance of the Liner is also rneasured- The pull- testing apparatus is shown in the following Figure 1. / Pull Yoke n Concrete Slab ' Pu11 Plate Mineguaed Lining Figure 1. Configuration of pull test apparatus [Archibaid,
35 Two types of pull-plates were used at the underground trials at INCO: solid plates and perforateci plates (Le. solid plates that were drilled full of holes, to dow material infiltration). In addition, two sizes of plates were fabricated for the pull tests: 125 mm diameter and 254 mm diameter. The plates were 0.3 mm in thickness. Two pull-testing procedures were used, for each type of pull-plate, respectively- Solid Pull-Plate Test Procedure: A thin layer of grease was used to coat the underside of the solid piate in order to prevent the polyurehane liquid h m seeping under the edges of the plate. In this way, the pull-testing pmcess allowed for the measurement of the tensile strength of the material. Once greased, the solid plate was placed directiy on the substrate surface and sprayed over with the MineguardTM formulation. The Liner was permitted to cure for 4û-hours at which point the pull yoke was attached to the pull-plate and the materid was slowiy jacked hm the substnte surface. The hydraulic pressure and deformation readings were recorded throughout the pull-testing process until the liner failed. Deformation readings were obtained with a hand-held scale. The configuration of the testing for solid plates is shown in the following Figw 2. Applied Pulling Force.t Bol t \ / Pull Plate \ Concrete Slab Mine& plate and pulling yoke assembly ) Figure 2. Solid plate installation and puhg configuration [Archibald, \ Liner (berween pull 14
36 Perforated Pull-Plate Test Procedure: The substrate surface was sprayed with a thin coating of MineguardTM. The perforated plate was then immediately placed ont0 the liner surface, and pressed into the Liquid M.heguardTM material. In fact, the plate was pushed into the Iiquid, causing some of the liquid to become extruded through the plate perforations. Once in place, the perforated plate and surrounding rock surfaçe was coated with MineguardTM again. The liner was permitted to cure for 48-hours at which time the pull yoke was attached to the pull-plate. The pull-plate was slowly jacked away from the substrate surface using the pull-test apparatus. The hydraulic pressure and deformation readings were recorded throughout the pull-testing process until the liner failed. Deformation readings were obtained witb a hand-held scale. The configuration of the test set-up for the perforated pull-plates is shown in the following Figure 3. Applied Pulling Force Bol t / Pull Plate \ Concrete Slab \\ Mineguard Liner (between pull plate & pulling yoke, and pull plaie & concrete slab ) Figure 3. Perforated plate installation and pulling configuration [Archibald, During plate pull tests, both pulling force and ram displacements perpendicular to each slab surface were continuousl y measured until membrane failure was observed. Resistance to plate deformation was demonstrateci by a combination of layer adhesion to the slab surfaçe and by shear and/or tensile resistance to plate displacement through the layer itself.
37 In al1 pull tests, an initial high level of raistance was mobilized due to the adhesion bond created by Minegu- layers between the pull plate and slab daces. Typically, maximum pull resistanœ due to adhesion was realized following plate defonnations of 1-0 cm or les. At plate deformations greater than this, loss of the adhesion bond was noted to result either by Glure of the slab surfâce material (still adhering to the Mineguard'W layers) or by debonding of the MUiegumP FR layer h m the slab dace- Following adhesion bond failure, continuous pull rsistance was generated by the strength of the material existing about the perimaer of each pull plate, through which the plates were pulled. Plate deformation fier adhesion bond failure was accompanied by considerable stretching and elongation of the perimeter MineguarP materiai, at displacements up to 7.0 cm. At displacements pater than this, partial or complete shear failure through layer coatings at the plate perimeter boundary was obsmed. The first underground test site at N O is located at the 260 Level (793 m) in the 2105 crosscut. The development heading's dimensions are 4.3 m by 4.3 rn The excavation is sprayed with ~ineguard~ on the walls and back for a distance of 7.9 rn dong the heading and the fàce is sprayed as well. Prior to the Mineguarfl application, the excavation is supported with mechanicaily anchored rockbolts and screen. The screen is systematically ait down as the application of~ineguard~ takes place. The second underground test site at INCO is located at the 2600 Level(793 m) in the 2280 crosscut. Again, the test site dimensions are typical of a development round: 4.8 m (15.7 fi) in width by 4.0 m (13 A) in height. Minegu# is applied to the rock dace for a distance of 6 m (20 fi) fiom the &ce. The back and walls are coated, as well as the face itself. As with the previous trial, the excavation is initially supported with 1.5 m (5 fi) danical anchored bolts with screen. The scceen is completely removed fiom the back and walls before applying the liner. As weil, the excavation sudice is cleaned using high-pressure air jud prior to the bfineguard'im application.
38 MIROC TM #2 muab The test results, corrdnting to the List of objectives, are swnmarized as follows: Air Quaiity, Concentrations: MD1 = 2 ppb at the ke; MD1 = ncgligiile do-wind the face; TEA & polyisocyanates = negligible at di sarnpling sites nom Ventilation Rate = c h (241 m3/min) Partiailate Concentrations = 10.3 mg/m3 at the face; 5.4 at 15 m downwind- Large amounts of overspray at the îàce are likely due to the close proximity of the ventilation discharge location to the spray nozzle; the overspray constitutes the partiailates that werc measwed at the aial site. Application Rate = 1.47 m2/min Coating Thickness = 1.58 mm Application Coa = 17.50!Vm2 (S CAN 1992) Joint Mttration = Good; Joint Spacing < 5 mm Support Capabilities: evaluated using pull-tests (solid & pdorated pull-plates): 2. PuII-Test, Peak Load = 2.75 kn (for a 125 mm diameter solid plate and 1.8 mm thick klineguardm) Suspension Capacity = Peak Load / Plate Diameter, pet mm of liner thickness = 7.05 Wm for 1.8 mm thickness = 3.92 Wdmrn
39 3. Pd-Test, Peak Load = kn (for a 254 mm diameter solid plate & 5.0 mm thick ~ineguard~) Suspension Capdy = Peak Load / Plate Diamder, per mm of Luia thickness = 2.59 Wdmm 4. PuU-Test, Peak Load = kn (for 3-26 mm thickness and 254 mm diameter perforaied pill-plate, whm plate area = m2 ) Adhesive Strength = Peak Load / Plate Area = 0.4M MPa (adhesive strength is irrespective of liner thickness) Blast Durability: the ~ineguard~ liner was extensively damaged by tly-rock during development round blasting- The poor liner pedomce was suspected to be caused by improper mwng of the two Liquid components, as a result of the high ventilation rate during application MlROC Trial #3 Results The test results for the second trial at NO'S Coppet Cliff North Mine, relative to the ove& objectives, are summarized as follows: Air Quality, Concentrations: MD1 = 66 ppb at the tace; MD1 = down-wind fiom the face; TEA & polyisocyanates 4 negligible at al1 sampling sites Ventilation Rate = dm (24 1 m3/min) Particulate Concentrations = 12.7 mg/m3 at the face; c10.0 mg/m3 at 15 m downwind. Large amounts of overspray at the fàce were attrïbuted to low ventilation rates. Application Rate = 1.77 m2/min Coating Thickness = 1-69 mm
40 Application Cost = S/rn2(s CAN 1992) Support Capabilities: evaiuated using pull-tests (solid & pafocated pull-plates): 1. PuII-Test, Peak Load = 6.45 kn (fôr a 254 mm diameter solid plate and 3.8 mm thick ~ineguard~~) Suspension Capacity = Peak Losd / Plate Diameter, per mm of liner thickwss = 8.08 Wm fbr 3-8 mm thïckness = 2.13 Wdmm 2. Pull-Test, Peak Load = 3.48 kn (for 125 mm diameter perforated pull-plate) Adhesive Strength = Peak had 1 Plate Ara = 0285 MPa 3. Pull-Test, Peak Load = kn (for 254 mm diameter perforateci pull-plate) Adhesive Strength = Peak Load 1 Plate Area = MPa Blast Durability: the ~ ineguard~ liner was extensively damaged by fly-rock during development round blasting. The poor iiner performance was suspected to be caused by inferior strength characteristics (due to miniature bubbles in the Liner) and irnproper mixing of the two liquid components. Liner Application: rnixing problems were encountered with the application whereby some of the resin product did not read with the isocyanate liquid. As well miniature bubbles formed in the liner. These bubbles are believed to be caused 6om the reaction of water with the isocyanate liquid. Specifically, the mixing of water (which could be present directly on the rock sufice or which could exist in the air with high humidity levels) and isocyanate liquid forms C a gas. The Ca gas fom the small bubbles in the rapid-curing liner. These bubbles cause the liner to loose some stifoiess and strength and it is possible for a human to physically rip the liner tiom the rock wall.
41 132.3 Summa y of Underground Triais The defined test objectives wac met during the three underground trials, as part of MiRûC's Phase 2 Study. The main find'igs are sumrnarized as follows: 1. A thin application is achieved with a fhst application nite (averagïng 1.6 m2/&). 2. The cost of the application is 18 ym2, on average (S CAN 1992). The rnajority of the cost is attxibuted to the expense ofthe mateaiai (80%). 3. Pull-testing, using solid and perforaid plates, was conducted at the two INCO triais with a sumrnary of the results in the following Table 1 : Table 1. Pull-test results f?om underground trials at INCO Limited wercer, ADHESIVE Peak Loads Displacement Plate Size Thickness Adhesive Sttength STRENGTH 0 (mm) (0 Y -1 (mm) W a ) (defined as: peak load / plate ara) SUSPENSION Peak Lods Displacement Plate Size Thickness Suspension Capacity STRENGTH OCN) (mm) (0 Y (mm) Widmm) (defined as: peak load / plate diameter) 4. The application equipment is appropriate for underground use; however, a more robust system is advisable for long-tm use.
42 Environmental testing in the worimom found that there are airborne toxicants when ~ineguard~ is applied: MD1 and particulates. The impinga method of testing for MD1 is recommended while the Autostep Jtaining mdhod was found to be inaccurate. The material long-term behaviour was not evaluated. Dilated aictureq up to 5 mm in span, muid be filled with Mineguardrar. Use of vermiculite, as a topadng, assisteci in gapping spans greater than 5 mm. The ~ineguard~ pedom poaty in development headings dumg round-by-round blast hg. ûther related findings were also determined over the course ofthe underground trials: 1. The isocyanate component of ~ ineguard~ is highly reactive with water. Even srnall amounts of water cause the isocyanate to react, forming COz gas and creating a foarny srnichire to the IMineguardTM Liner rather than a noncellular structure. The reactivity of the isocyanates with water is a conceni for underground applications where the rock SUlfàce is generally damp and the air humidity is usuaily very high. Further investigation into chernical additives has been recommended, to reduce the isocyanate reactivity with water. Urylon Chernicals initiated research of the chernicai formulation, under Phase 4 of the MIROC Program, to investigate a means to rnitigate the effects of watedhumidity in the application environment. 2. The material adhesive strength of the liner was questioned, when used with various substrates. Phase 4 of the MIROC Program was intmded to also investigate the material strengths when applied to various rock types and within various humid environrnents. As such, laboratory pull-testing was instigated to provide additional information to these questions.
43 In summary, one signifiant process detriment was observecl. during early site trials: when spraying under conditions of high relative humidity, estimated to be at or pater than 70%, Mineguardnr layer bubbling was noted. Theclusion of gas, in the form of carbon dioxide created when MD1 reacts with moisture in mine air, was observeci to produce a porous MinegpanP coating. Such porous coatings were judged to adiibit more plastic behaviour, lower density character and degraded strength capab ilities t han origindly desired, thereby dccreasing potential adhesion bonding capacity between the coating and rock surfaces. With an understanding of the liner shortcornings, a propsal fiom Queen's University was accepted by MIROC for iùrther evaluation of the MineguarP liner's strength properties within a range of environrnents. As such, the Phase 3 Underground Testing was postponed until the Phase 4 testing had been completed. The fourth phase of testing was conducted in 1991 and The work çonsisted of laboratoiy pull-tests of the hvo-part polyurethane coating, h4ineguardtmtm The tesîing, as fùnded through MIROC, was conducted at Queen's University Mining Engineering Department to fùrther evaluate the material adhesive and material strengths. This work was undenaken by R Mercer wercer, pnor to proceeding with the MIROC Phase 3, which involved additional underground trials. The problem of the reaction of MineguanP with high humidity, as experienced during the underground field trials, was addressecl through a controlled laboratory investigation. A series of concrete, granite, limestone and sandstone slabs were coated with Mineguarm at thicknesses approximating 1.5 to 2.0 mm, while varying the relative humidity conditions during cure.
44 ûvdl, the Phase 4 work is ccimpnsed of two testing programs: Part 1: laboratory pli-tests to define the adhesion quality within high humidity environments Part 2: additional laboratory pii-tests to me<hods of reducing the effects of humidity Part 1: Laboratocy PuLTcsting The pull-tests were required to address the following concerm with Mineguardm: 1. What is the efféct ofhigh levels of hurnidity on the material strength parameters? 2. What is the effect of rock type (substrate material) on the adhesion of the liner? 3. If necessary, what chernical alterations can be made to the ~ ineguard~~ matenal in order to allow for applications within elevated hurnidity levels? The pull-testing experiments were designecl to quant* the effect of water on the liner's material properties. Primarily, the entraprnent ofcarbondioxide bubbles within the Liner (due to the chemical reaction of isocyanaîe with water) is felt to duce the adhesive bond strength between the liner and the rock su-. As well, the bubbles are thought to reduce the overall strength and toughness of the Iiner. The Phase 4 pull-tests were conducted in conjunction with U~ylon Plastics Inc-, in Guelph, Ontario, in November 1991 and Febnrary The pull-test apparatus, itself, was designed by Queen's University Mining Engineering Department. Refm to the previous section, i.e. Phase 2 Tests,for a complete description of the apparatus and pull-test produre. Instead of using inhomogwous rock surfàces as the testing substrate, a more unifom concrete substrate was used. The rationale for using ancrete is that the effect of humidity on the adhesive strength could be more acarrately defined if the substrate is as unirom and consistent as possible.
45 Al1 test slabs wexe sprayed within a controlled environment, in a spray booth, with va15ous relative humidity (RH) bels, primarily ranghg hm 35% to 98%. The spray booth environmental conditions were rneasured ushg a hand-held Vaisala Humicap Humidity Meter caiibrated to an acairacy off 1.0 OC and f 1.U?? RH The temperature of the potyurethane cornponents, A-Side and B-Sidc, were monitored during application to ensure the apptied product was the same for d specimen tests. The pull-plates used in aîi laboratory testing were 254 mm in diameter, with five paforated plaies and five solid plates used in each test at a specified % RR All plates were putled within a two to four hour time period irnmediateiy after spraying, to ensure a consistent cure time had elapsed for al1 tests. Five humidity levels were used to conduct the pull-testing. As well, for each humidity level, material strength tests were conducted by Urylon Plastics using ASTM standards. Su samples were retained for each humidity test to rneasure tensile strength, stiftiiess (Young's Modulus), and percent elongaiion Using the pull-test results, accurding to Merca , the adhesive strength can be determineci by dividing the peak loading force by the area of failure beneath the pdorated plates. Mercer justifies this caladation by stating "the peak loading force always ocarrred just pnor to adhesion fàilure beneath the pull plate and the contribution of the lining material around the perimeter was at the time comparatively srnaii." This statement is not compktely correct. Thae is adhesive force at work beneath the plate; however, there are forces also at work beyond the plate periphery. The area over which the loading forces are adng is greater than the plate am As weli, there is a tensile cornponent at woriq at the edge of the plate. Mercer assumes this to be an adhesive sbength parameter only. A tme adhesion test would require that the iiner beneath the plate be the only region king pulled. This c<xild have been achieved by cutting through the lier at the plate's edge, and then pefioming the pull-test [Sutherland, This new adhesion strength test pdure has been designed and used by Dr.Dwayne Tannant of the Geomechanics Research Centre at Laurentian University.
46 Mercer  also states haî the lids shear strength is calculated by dividing the peak loading force by the product of île solid plate perheter and the thickness of the liner. The test procedure is a mesrsure of the liner's tensile strength, as opposed to a shear strengih cornponent. As identifieci by Mercer , there were sorne problems with the pull-testing: The puii-test apparatus only has 5 cm of travel; therefore, in some cases the MineguardTM liner did not Mf at the fill extension ofthe puüing-yoke. Some tests showed the liner to tear, but only parti*ally, at the full 5 cm extension. In these cases, the liner thickness was measured at various points along the perimeter and then averaged. Due to uneven thicknesses of iiner, the pulling-yoke would bend and cause uneven aistriiution of forces on the pull-plate and substrate. This would provide concentration points of force and could have causeci prernature nipture. At high humidity levels, not only does the adhesive strength vary, but the strength of the material itself would also become affected. Identification of the source of lower material property strengths would become difficult to isolate because of this double-reaction Results of Eumidity Tcsting on Concrete Slabs As expected, peak loads decrcase as the humidity levels increase. There is a marked decrease in adhesive strength for MineguardTM that is sprayed a! relative humidity levels above 66%. Matenal strength (tensile sttength), determined using the solid pull-plate technique, shows a uniform decrease in strength as humidity levels increase.
47 Labonitoiy puil-test rcniltr dect the observations and values m d during underground trials. The test sites at INCO were obviously vecy humid thus causing the low peak load readings during pull-tcsting. Mercer's plotted results are summarizcd in the following Table 2. Table 2. Adhesion and material strengîh testing: variations with humidity IeveIs, taken nom Mercer ADHESION TESTS: Humidity Level (%) Adhesive Strength ' (hilpa) Note: perforateci pd-plate resuhs ' adhesive strength = peak load / plate area MATERIAL TESTS: Humidity Level (%) Tensile Note: solid pull-plate results tensile strength = peak load / plate perimeter 1 plate diameter = 254 mm 2 plate diameter = 254 mm
48 Additional test results wercer, and [Urylon, are sumrnarizeû as foliows: Testing completed by Urylon Plasrics for the tensile strength, Young's Modulus and the percent dongation indicate that only the tensile strength is dependent on the hurnidity of the spraying conditions. At humidity levels above Wh, aii sarnples exhibit a foam-like structure due to the entmpment of tiny bubbles in the liner (fiom the development of Ca gas, cteated nom the chernical reaction of water and isocyanate). The deterioration of material strength with an increase in the humidity level is believed to be due to the presence of the tiny bubbles in the liner Results of Humidity Testing with Rock Substrates At the completion of the humidity testing with concrete blocks, a second set of humidity testing was conducted wercer, 19921, as descrii hereunder. The second phase of tests was designeci to evaluate the influence of the substrate materid and humidity on the Liner's adhesive stnngth. Mineguardm was applied to various rock specimens of the foflowing types: granite, sandstone and limestone, 4th a range of humidity levels: 66, 78 and 90 % RH The results of the substrate testing are summarited as follows: The adhesive strength is dependent on the substrate material, refer to Table 3. The highest strength values are obtained with the granite specimens folfowed by the sandstone and then the limestone rocks. The sandstone results closely match the results tiom the phase one, using concrete dabs.
49 Tabfe 3. Summary of adhesive strength values for varying humidity levels and substrate materials, as denved fiom Mercer  Rock Type Granite 1 Hwnidity Level (?A RH) 1 Aâhesive Stmgth (MPa) Sandstone Lirnestone At vexy high humidity levels, the porws substrates (ümestone and sandstone) exhibit a higher adhesive strength than the fine-grained rock (granite). The granite, unlike limestone and sandstone, is unable to absorb the freestanding moisture to auow an excellent bond to fom between the rock and the ~ineguard~ liner. In some tests, the puil-test results in a thin layer of rock being pulled off the rock slab, rather than the liner king pulled cleanly fiom the rock su*. This implies thaî the Nlineguardlh' to rock adhesion strength is higher than the tensile strength of the rock specimen itself This cdd be a conceni for weak, fiable rockmasses, where the rock fails in tension (behind the MineguarcP liner). The material strength dues for wying humidity levels and different rock types have been obtained. The results indicate that there is a uniform decrease in strength as the humidity level increases, Table 4.
50 Table 4. Uaten*a! strength values for varying humidity levels and substrate matmais (taken fkom Mercer, [1992l) Humidity Level(% RH) Mataial Strength I I Summary of Labontory Pull-Testing The adhesive strength and materiai properties of the Mineguardriw liner are adverseiy affected by: 1) high humidity levels and 2) varying substrate matenals. Some consideration is required for the use of MineguarP on very weak and/or fnable rock types. Furthennom, the affect of high humidity is a serious problem that wanants Mer investigation on mitigating mechanisms for elevated humidity levels. This new research was undertaken by MIROC under Phase 4 of the testing program [Mercer, P?rt 2: Humidity Miîigating Techniques Following the results of poor a i o n of the liner to rock surfàce, under elevaîed humidity levels, an additional area of d was undertaken through MIROC. This part of Phase 4 is aimed at investigating rne<hods of mitigating the effi of elevated humidity levels on the Mineguararicc liner.
51 1. PrPheat the subsbate surfirce to irnpmve liner to subsfrate adhesion by: a) reducing the Surface moisture content dot b) reâucing the set time of the liner, in an attempt to prevent chemical reactions h ocauring between water and isocyanaîe liquids. 2. Utilize chemical additives for the MineguarP formulation, to prevent the chemical reacîion of water with isocyanate Iiquid Surface Hcating Experimentation For this testing program, 254-mm diameter perfiorated pull-plates were used to obtain the adhesive strength parameters Conctete slabs were used as the substrate for application of MineguarcP. The testing procedure involved the pre-heating of each concrete dab for a period of 1 minute immediately pnor to spraying. The temperature of the substrate is measured using a Cole- Parmer Mode1 L infjared &e heat sensor with an accuracy of t 1 OC. As well, the rnoisture content on the concrete is rnes~sured (just prior to the MineguarP application) using a Delmhorst Moistwe Tester. The rnoisture readings are in gauge percentage, for a comparative anal ysis on1 y Chernical Variation Experimentation Urylon Plastics developed two patentid humidity-resistant variants to the original MineguarP formulation, and narned these versions as Formula 104 and MineguarP HH453, Laborato'y pull-tests were perfomaed on each liner formulation, using the perforated plates, 254 mm in diameter, for a range of hurnidity levels. As well, pull-testing was performed using the MineguarP HH453 variation with the substrate heating procedure.
52 Cornplete and dded rcsuits are tabulateci by Memer [19923, with a sumrnary provided hereunder: Adhesive sbength is somewhat improved when th substnite is pre-heated, particularly at humidity levels above 66% RH Resuhs of the testing are tabulated in Table 5, as deriveci fiom Merçer Table 5. Adhesive stragths with Mineguarfl variants for varying humidity levels Chernical Variant Humidity Level (Y0RH) Adhesive Strength ' (MPa) Original MineguarP + Heat MineguardTM HH453 + Heat Adhesion results for Formula 104 are inferior to those obtained with the original MineguardTM formulation.
53 a nie Mineguard"' HH453 variation provides the kst pafomuure for adhesion, as wmpared to the ai*ginai fanuation, and the original formulation with a heated &strate. Material properties have been determined for each chernical variant, for a range of humidity levels. For cornparison, the Mineguardrrr formula gendly exhi'bited lower strengths than the -453 version, as follows, Table 6. Table 6. Material properties for Mineguarariic versus MineguarP HH453 variant: omrgcd for RH betwea 3û% to 95% [Mercer, Tende Elongation (Yo) Young's Moduius (MPa) In most cases, with low humidity, the substrate Failed before the liner to rock adhesion was exceeded. In tàct, a thin layer of rock would be pulled f?om the concrete slab at the moment of fàilure. O Al1 liner variants exhi'bit a terisile, brittle fàilure at the pull-plate edge, with low relative humidity ranges. At higher humidity levels, the limer failure is a tearing mode, with considerable "balloonin~ of the üner at the pull-plate edge. This would indicate that the liner becornes more elastic when applied in highly humid environments. Compared to the original Mineguarariu formulation, the MinegurdTM HH453 exhibiteci a reduced elongation capability. Typical results of the adhesion pull-tests, versus those obtained for the original MineguarP FR materiai, indicated that no detrimental adhesion bond strength effects were reaiized for the Hfi453 material at any relative humidity condition up to and including 98% relative humid ity.
54 At al1 humidity levels, the HH453 formulation exhibited equal or better adhesion response than did the original Mineguard'W FR matmal. Overail, the Mineguardrw HH453 tormula!ion was deemed the superior variant for mitigating the effects of hurnidii. The resistance to elevated hurnidity levels was achieved at the expense of lower elongation capabilitics. Urylon Plastics altered the formulation again, and produceci two alternative humidity resistant products: MineguarP FE549 (for inaessed eiongation) and Mineguarariw Hi3456 (for decreased elongation). The results are summarized hereunder: The new variants provide i n d elongaîion, as compared to the original formulation, however the material stïfbess is reduced. Adhesive strengths, for a range of humidity levels, are similar between ail variants. The two new variants, HH454 and HH456, have lower tende strengths than the HH453 version. As a result of ail testing the MineguarcP Hi3453 version is the recornrnended variant for use, to aliow for rnitigation against humidi effects. As compared with the original formulation, this version represents a liner with high tensile strength, high Young's rnodulus (stifhess) with ody a dightly reduced elongation capability. Further analysis, exarnining the dect of humidity and surfàce moisture on adhesive strength, was undertaken in This work indicates that su& moisture is a greater detrhent to adhesive strength, as compared to hurnidity aione. It is determineci that the relative humidity itself is only a problem for the MineguarP application in that the humidity causes the formation of moisture on the rock surfàce. In addition, adhesion loss may be a problem in low hurnidity environrnents where the rock surfiice is wet due to washing down the suriàce for geology.
55 The approach of heating the substrate provides increased adhesive strengths with the pd testing- The original hypothesis fbr heaîïng was îo hcrease the set* time, to duce tirne for chemical d o n s betwecn airborne water and isocyanates. However, substrate heating is believed to provide a reduction in sudkc moi- (to enhance aâhesive strength) rather than lowering the set-up tirne for the liner. 1. Elevated levels of hurnidi and surf& moisnire on the substrate surface will decrease the adhesive mmgth of the ~uieguard~ ha. 2. Substrate strength and surface conditions (such as dut, dii roughness, porosity, wetness, etc.) will Séct the adhesive strength of the lmineguardtm liner. 3. MineguarcP HH453 variant is superior for use in elevated humidity environments Summary of MIROC Phrw 4 Testins The results fiom Phase 4 of MIROC pull-testing identified the MineguardTM HH453 formulation as king a superior podud for use underground, as compared to the original MineguarP. The new chemical formulation allows appropriate strengths to be generated when used in humid environments. In fâcf chemical modification was shown to overcorne performance problems associated with exposure to high levels of relative humidity, which are known to exist in underground environments. In dl subsequent applications, the formulation known as HH453 was adopted and Iicensed for use unda the product name Mineguard'w. Installation and cost information obtained during this MlROC -ch phase was also used to provide a cornparison of operating factors for the thme principal area suppon techniques currently in use or proposed for use by underground mine opecators. Such infiormation is listed in the next section of this thesis, mnceming produdvity and economic analyses. A recommendation to proceed to Phase 3, with the second set of underground trials, was made at the conclusion ofphase 4.
56 in April 1992, the N hepmp HH453 üna was appüed to an underground excavation at INCO's Copper ClinNorth MUr The details of the investigation were written by Mener  and are ~ummamrd herainder- The objectives of the underground aial am as follows: 1. Evaluate the appiication of the Mineguard" HH453 product in the underground environment, 2. Evaluate the cost of the application, and make a cost cornparison between the original MineguarcV formulation versus the new HH453 version, 3. Evaluate the in situ performance of the HH453 liner in the underground environment. 4. Test the air quality during the underground application of MineguarP HH453, and provide a cornparison with the earlier MIROC test results. 5. Evafuate the blast survivability of the HH453 formulation liner Undergruund T M at INCO's Copper CW'f North Mine: The MineguardriH HH453 produa was sprayed at the INCO Copper Ciiff North Mine at the 2600 Level, in the 2240 crosscut. The heading was typical of a standard development heading at NO, 4th approximate dimensions: 4.3-m in width and in height. The heading was developed 24.2 m in l ena with standard INCO support of 1.5-m rockbolts and screen. The bolts were installed on a l.gm square pattem. Only the last 12.7 m (back and walls) of the heading was coated with MineguarcP HH453. Prior to the liner application, the meen was removed f?om the A s and back and the excavation surface was thomughly washed down. 36 hours elapsed 60m the completion of washing until the application took place. A ventilation fan was installed approximaîely 18-m fiorn the hce, supplying air into the heading at a rate of 1 13 m3/min (4000 cûn). This fan aided in drying the rock surface.
57 M3ROC Phase 3 Resulb The test results for the MIROC Phase 3 underground trial at INCO's Copper C m North Mine, relative to the ovd objectives, are swnmarized as fotlows: Air Quality, Concentrations: MD1 = 32 ppb at the fke; MD1 = negligible down-wind fiom the face; TEA & pdyisoqanates = negiigiile at al sampling sites- Due to the low readings obtained during this td,it was recommended by Merca [lm] that the n d for Scott Airpacks for the application personnel be re-evaiuaîed with a suggestion of ushg charcoal filters in place of posïîive-pressure air fesd It is Uus wthor's opinion that the results fiom one trial would not warrant the elimination of the positive-pressure facemasks, although an altemative air-fecd system should be researched, to reduœ nodeman fatigue. VentiIation Rate = Crin (1 13 rn3/mh) Particulate Concentrations = 5.25 mg/m3 at the fàce Application Rate = 0.9 m2/rnin (slow rate due to down-times with the xissor-lifl truck) Application Cost = $/m2 (S CAN 1992) Adhesive Strength: in cornparison with earlier MIROC testing and laboratory resdts, the underground pull-test mlts were the lowest (ranging between 0.4 to 0.78 MPa). iaboratory Testing: test sheecs were sprayed at the underground site and sent to Urylon Plastics for tende sbength tests, percent elongation measurements and determination of the Young's Moduli. The riesults were al1 lower than the values measured previously in the laboratory application.tes&s.
58 - Support Capabilitia: evaiuated using puil-tests with paforaied pull-plates, with a plate diameter of 254 mm Rcailts are tibilstrd in the fouowing Table 7 [Mm, Table 7. Pull-test results fiom MIROC Phase 3: undagniund triil at INCO Lhited, Copper CliffNorth Mine [MM, NA JWA N/A N/A N/A N/A JWA Relative Humidity: the hurnidity was recordecl at the test site, with an average value of SC?? for the duration of the application. Humidity levels increased approximately IV!& during washing of the heading. The hurnidity slowly rrtumed to background Ievels afier several hours had elapsed since washing. The earlier MIROC trials experienced much higher humidity Ievels, hence of MineguarP HH453 was not adequately tested for such elevated humidity levels. Temperature Readings: the excavation rock &ce varied fiom 1 1 OC to 14OC. regardleos of surface moisture conditions. The rock suriace was essentially equivalent to the arnbient air temperature.
59 Blast Durability: the Mrneguardm üm was damaged by fly-rock during developrnent round blasting. The damage was les than that arperience during the Phase 2 MIROC Underground Trial. Ovecal, the liner wss noted as "not able to completely resist impact associateci with a scandard dcvclopment blast in close proximity." Liner Application: due to the height of the headii a scissor-lift truck was used to apply the MineguanP HH453 to the back of the excavation. From the sumrnary of the trial, it was indicated that the application of the liner was hindered by the requirement of using the scissor-tift ûuck nie mtes h m the trial also indicated probiems with the nozzieman's supplieci air, with an insufficient tirne period of 20 to 30 minutes per canister for the Scott Airpack system. Furthermore, the weight of the air packs caused fatigue to the application personnel. In addition to the MIROC gnnind support research of the MineguarP product, some additional research and testing was conducted in conjunction with Queen's University. The primary interest in MineguarbY was for area support of rock; however, the MIROC testing identified other possible benefits to the mining industry. Specifically, these sojoums were directed at po tential uses and applications for thin pof yurethane coatings. The summaries of the additional research are providecl hereunder, as taken from a technical publication [Archibald et. al., Rock Deformation Indikath Tesîing The capability of MineguardTM coaîings to provide visual indication of rock deformation was examined. In these trials, brittle coatings, such as enamel paints, were applied ont0 MineguarP membranes following t heir installation ont0 rock surfaces. Li rnited field trials of this deformation sensing technique wae attempted at the Bousquet #1 Mine in the Province of Quebec. Mons of MineguarP-coated drift walls and backs were enamel sprayed and obsewd over a three-month trial intend.
60 No indications of gnnind movemen& evidenced by mating fiacturing, were noticed, however. The sites of covaagt were subsequently fwnd to be locaîeâ within a zone oaupied by the mine shrft pillar, and therdiore not uifluericed by high stress change nor active rock deformation For this mason, nunimal coating reaction to rock deformation was created and succesdùl completion of in-situ trials was problernatic Radon Gas Buricr Tating An additional study was conductecl to evaluate other non-support-based benefits that could resdt fkom use of MùieguanP materials in underground mines. One principal benefit examined was the potential blocking capabilities of MineguarP for contaminant gases [Archibald & Desouzo, 1993; Archibald, and of Rockguard [Archibald, A contaminant gas of concm in mining is radon, which occurs naturally in both uranium and non-uranium mines. Radon is capable of diffising through porous rock into mine openings and generating worker exposure at levels above regulated occupational limits (Le. should appropriate ventilation controls not exist). Traditional area support media, such as concrete or shotcrete, offer minimal resistance to difisive movement of radon into mine workings. Such materials are du, unable to penetrate and seal fractures when applied to rock surfaces. Pol yurethane coatings, alternatel y, have dernonstnited the abil ity to penetrate rock fractures significantly, when sprayed in liquid foxm, and to seal fractures when cured. Radon gas permeabiiity trials were canduaed using MineguarP and Rockguard polyurethane liners. From this wodq a proportionality parameter (R) was calculated and used to detennine the potential radon blocking capacity of the liners in the form: Bad upon laboratory measurements, typical polyurethane layer thicknesses of 1.0 mm were demonstrated to be capable of blocking difisive flows of radon by approximately 99.85%.
61 A separate program of laboratoty research was initiated to assess fiction fiictor (K) parameters associateci with Mineguaranccoated airway passages. The principal benefit under investigation was the poteiitiai ventilation flow resistance reduction [Archibald & DeSouta, and [Archibald, 1993aJ- Estimaîed fiction fhctor parametas, developed h m ainway analogue measurements and listed in Table 8, indicated that considerable potential exists for fiction factor reduction within mine airways that may be subject to MineguarP installation. Table 8. Friction fàctor (K) results for coated plywood airway The fmai phase of additional testing of MineguardTM was conducted to evaiuate material resistance to long-term environmental degradation due to exposure to chernicals, severe temperature variation and the like. MineguardTM was subjeded to artificial aging and exposure to strong acid and base solutions to determine chernical resistance properties of this material. Acid immersion tests for artificially-aged materials indicated that MineguarP would suffer tensile strength loss (25%), increase in tensile elongation capacity by 25.35% and some small masure of weight gain. No si gni ficant différences in physical behaviwr change were dernonstrated between ten and fifkeen-year aged samples. Gendly, similar physical behaviour change was also noted to ocau when MineguatdTM materials were immerd Ui alkaline solutioa Typical test results are listed in the data of Table 9.
62 Table 9. Materiai aging and chernical resistance characteristics of MineguarP Shore 90A 80A Hatdaess Assessrnent of the potential use of MineguardTW as a Surface tailings cover agent and an Acid Mine Drainage (AMD) mitigator was also undertaken based on laboratory investigation and industry surveys [Archibald & Lausch, The principal objectives of the review were to detemine whether industry use of this dry cover technique would be acceptable and whecha positive physical attributes existe- for promting MineguarV as an efféctive AMD bhcr. The installation cost for MineguardN was estimateci to be approximately $165,000 (S CAN 19%) per hedare of tailings covered, including al1 labour, raw materials and new spray equipment purchase costs. In order to operate effectively in harsh Canadian climatic conditions, AMD banier materials must resist significant temperature extremes, mtably mld weather effects, without physical degradation Accordingly, MineguanP materials were subjected to tensile arength and elongation capacity testing under both ambient and extreme low temperature (40 C) conditions. No significant detrimental alteration of MineguardN physical charaderistics was observeci.
63 Additional tests were utilid to assess Minegud'9 oxygen gas transmissivity Md water vapour transmission rate chuidaiaics. Where barrias can be shown capable of dcting oxygen and moishûe flow into and through Mnarlïzed tailha dcted AMD g d n ocairs. For 1.0-mm thick Min- Iayers, the oxygen gas transmission (OGT) and 3 2 water vapour tmnsmissivity 0 rates wae mmed as 29.0 cm Im î24hrs and 0.05 dm2/24-hrg respectively. A hydraulic oadudivity parameter was derived for this matmal, with a value appforrimating 5.80 x 1 0 mis. ~ ~ Overall, Mine# wu shown to exhibit vay fivourable physid chataaeristics for use as an AMD dry cover barriq though at a cos& which cumntly exkts in the Md-tdiigh range of available mitigation technologies. From the research finded by MIROC, there are iùrther areas for reseafch, which have been identifid by the author of thk thesis. Whilst swie of these areas of tiaha rrse~rch have been diswsed pratiousiy, r complete summiq is provided haauda. niese items have k n generally graiped into three broad --ries of te~eatch, beiig (1) technical considerations, (2) operational considerations, and (3) pactical use considerations: 0 Technid Considcrations: Strength parameters need to be dearly dehed with specific testhg procedures. For instance, solid plate pull-tests mwre the force applied normal to the iiner acrôice rather than the material strength or shear strength of the membrane. Dehitive terminology and testing procedures need to be estabfished and comrnunicated to the industry. The methodology for tejting and defining &ive strength shaild be reviewd Additionai adhesive strength tcaing is fequired, ushg a sdid mefhodolow, to mnfum the rdts for aivimnmenial aspects and for wiais substrates-
64 P Pull-testing of wak substrates indiates that the rodc itself füls at low loadhg rates. ~sisacoacanwhen~isundrrthc~aippat~mui~ssof very weak rock conditionr (i-c. with high-gnde d v e guidelines in wak rock OOnditjolls n+d to k defined. dphides). Application P Problems with inherent liner strength and the liner to rock -ive strength, when spraying MheguuP in M d conditions, has raid a wncsn when spplying the liner to wet rock surfkes. P Kgh partidate readinm obtained during applications of MureguarP underground, were indicated by MIROC as king causeci by 1) high vdation mes in trial #1 at INCO, and 2) low ventilation rates in triol #2 at INCO. This contradiction requires fùrther investigation and definition. P Costing analysis by Mafer  for the wious underground trials indicate a range of costs fiom $31.07 to S17.50 per square medre (S CAN 1992). niese costs were obtained fkom indu* meys and are cunently out-dated- More detailed cosring is justified, with an undersbnding of the implementation of spray-on systems into the development pcoce~s, whereby an estimated spray time is indicated, including al1 potential stoppages and the requirement for additional supplies. P Productivity incmses, and alternative processes for support application, d to k exploreci nnthcr. In CO- 4th this analysis, additiod coshg and ecomrnic justification nads to be completed using currrnt mat data and tirne study information. P The requirement (or not) of a vertniadite coatlng needs verifkation Based on the findings, the produdivity and emnomics need to be identifid appropriately for the IFoUnd support system-
65 P Issues regarding the problems of (1) wata in the isocyanatc drums with potential plugging of the mde, and (2) a maximum 2û-minute dom time untii the gun and equipment need to be ckiuied with solvents, need to be addrrssed. The i s o b betweeri produaion are4s requires that the apiprnent be able to have longer than 20- minute stoppage allow~nas. P Transportation and storage issues, br the polyurethane Liquids to remain at a temperaave above 65 OF, need to be investi- fe~uired for Appropriate recommendations are storage, handlig and application of polyurethanes and solvents, and for the appropriate disposal of materials, solvents and empty drums. Health, safi and environmental coricenis need to be addrrssed, with the recommended pratocols for use of pdyurerhanes in confined u n d m environments. Flammability and off-gas testing needs to be furhr arplored, to clearly identm the risk (or not) of fim with the polyurethane liners. * Dissimilar test dts for Young's modulus, tende strerigth and percent elongation were obtained by MIROC' when the liner was tested in the lab and underground. There is a suggestion that the variation in values depends m the location of the application. However, it is also possible thai the quality control of the chernical formulation is suspect. This has not been fodly considered by MIROC in any of the testing programs, aithough there are comments made by Menrr  that lad one to believe that quality was becoming an issue. M m mes: (1) the spray equipment may require "stabiiüation" to obtain consistent LUia qualities and (2) "the factors contmiiing the performance of the pduct meguatm are d l not completely understood". Oved, the quality control aspect is an Unportant consideration for utüizing sprayon liners as engind support mediums. Spdc testing procedures and defineci limitations need to k cleariy defined
66 FuCsde implemmtahq with a system fm transportin8 the poduds to the underground Mi has nat been resolved. This includes a design of reusable containers (wihut the need for nitrogen blankets) and testing protacols to ensure now expird chcrnicals. Design of equipment for reanote-contrd or autord applications neds researching. The firture use of the application of MineguarP within teleminhg operations requires some uphnt research and design. Practicol Use Considerrîhns: Using the technical daîa, guidelines for appropriate use of the product for given applications need to bc detined- Alternative material reseafch should be an on-going process, with an aim to dect various candidate produds for a variety of u n d m and surîàce uses. For instance, a slow-setting and inexpensive latex materiai would be a prime candidaîe for replacing the scteen element of boits-and-screen support systems. The latex material may be a cdic&te for supporting the walls of blastholes and botehales, and pertiaps for largediameter raisebore holes, to vent sloughing and subsequent blockage of production holes and deterioration of ventilation raises.
67 PRODUCI'XVY & ECONOMIC ASPECIS The incentive to pusue spray-on lina mearch for gmund support is cledy roated in emnomics. Specioally, rpnyon support ailows fm the eiimnition ofconv«ttional support meuiods, which are both tim-g and labour intensive. The new mppoct priocess using sprayon liners, in tum, allows praduaivity to inaarc dnmrtically and, hence, fw realization of ecommic gains. The hunediaie upfkonî am-c bene6t of qiacing boit-end-scfetn support with spray-on linersmaynot beeady mqpkd bymineopntmduetothesubqt.ntli materhi costof the ha products themselves. Yeâ, once the produamty aspects are nilly considaed, the obvious down-stream economic benefits are undoubted and difficult to overlook Speafically, the rate of application Md setup times for polyurrihne Liners offm a means ofachieving fost development and reduced labwr asts iissociated with support installation. Furthemore, the number of accidents associated with screen installation at the fke would be eliminated and the need for rehabilitation may be substantially reduced with the use of liner products. In fa4 the mining inhisay an attribute the largest percentage of underground accidents to the handling and instaliation of mine screen [Summary Report, ONRSq It is also mmmonly acknowiedged that d active mining headiigs expience fiy-rock darnage to the previous round, in tems of ripping screen and loosaiing of mechanial-anchoreci bdts. As well, over time the screen support generally degrades due to corrosion and damage by heavy equipment. These ktm knd themsedves to seeking altemative products for screen, as a minimum, and ideally, for the entire Mt-and-screen system. Despite the inherent ecommic gains, it is also clear thaî the implementation of Jprryon support systems within the industry is taking an inordinate amount oftime to achieve. There are a number of reasons for the implementation delay, three of which are postulateci hereunder:
68 Firstly, co~nuniation of the psaial soiutions invdving spray- support has mt Eikea place. Much of the ltgwork and opntional hurdles have ban rchieved only through much effort and dedication of sorne major industry companes and rrsarch organido~. The original concept has neva ka, implemented into a vrakiiig system fa the existing mines. Fuhmme, once mcqpid, the rtusl impiemcnution rrquircs ample tune 0-e. in the order of y-). Saondly, a change in work pdces is mmully ~ccompanied by much resirit9nr h m the wrkers- niis is gaierally wnsidered to be a hum- trait that bas been, traditionally, difficuh to overcomeme Experience has shown the dvantage ofinvolvhg the workers in re-aligning a system and in implementing change. Ovaall, this mauu that all levels of an organuation must be acceptùig of the new technology. Thirdly, the vision of the use of the products must be an paxt of the rnining industry's research focus. Fa iiistwce. spray-on support is an option for rnining companies dedicated to automation research Thediore, since the automation equipment and processes are nat yet an integai paxt of the mining operations, there is a delay in the implementation of the spray-on liners. What must be rernembered during research and development is the final implemented systern In this case, a working system of automated equipment and pmceses, utilizing the spray-on liners for support of the excavations, allows the down-stream econornic benefits to becorne very promising, In fkt, the success of automation hinges quite cleady on the ability to use a qui& and easy means of aipporting the rodg withat personnel intervention. It is believed that the sprayon systems play a vital role in this type of rnining operation. Spray-on liners are intended to wok in conjundion with or to replace eaha shotaae or the saeen component of bolt-and-screen support systems in a variety of support roks. There are also situations and ground conditions thaî would warrant the full replacement of bolts and-screen with a spray-on liner.
69 The rapid-deployable liners offa considcnbk baknt fm mining or excavgting Opaatiom due to the rapid rates of application, ease of uuullaîion and ability to achieve gr- W? aire within seconds iffa application onto rock di. FurthenmKe, these liners allow for the achievement of rapid rates of drift advance and a high degree of automation than MineguarP support is similu in cos& to bolt-and-smm support meâhods, cheaper to install than reinforcd shotaere support and cm be applied et Wgnifidy higher rates than either altemate technique. In addition, the spny-on liner system offas low mwriai handling requirements and remarkable productivïty enhamement ptdal. Undergrwnd mine trials indicate that Mineguard"( exhibits significant potential for use as a short-term, stand-alone support technique (Le. to replace the need for mckbolts/rebar bolts). The spray-on liners dso demonstrate the capabidity to: (1) increase productivity in high speed driffing operations (where bolts-and-screen cannot be placed immediaîely aaer deve10pmcnt)~ (2) replace screen in standard bolt-and-saeen operaiions and (3) posentialiy mitigaîe excavation domage rcsulting fiom dynamic rock Mure abwt mine openings acted upon by high stress. Cwently7 the underground mining indusüy uses labour-intensive processes for supporthg the excavations. The most widely used support pocess is the installation of bolts and screen to the back and walls of exc8vations wing either hand-held drills, such as jackleg and stoper drills, or MacLean bohers, or other such equiprnent. The aurent bolt-and-screen support process is also time-intensive, resulting in a lengthy support cycle tirne. The econornic advantages of spray-on Iiners have been postulated, hm the cumulative effects of mining cost teduaion, throughput îhe deaerse, a d quility improwment nie ecommic and produdvity gains 8ssociated with spray-on liners are examimi in the next two dons.
70 The research work by MIROC includcd a brief aconmiic justification of using thin liners fm ground support. The installation and cost i nfion was assembled during the third stage of the MIROC test program, to provide a cornparison of operating ktm for three principal area support techniques: 1) bolting-and-saaening 2) two shotcrete variations (with and without steel-fibre ) - 3) MineguardrY These three support techniques werc &sen as the methods prunarily in use (and proposed for fllture use) by underground mine operators. A summary of the installation costs and other related infiormaiion, based upon a Canada-wide mullng industry survey, is lisced in Table 10. Table 10. Summq of support considerations [Archibald et. al., COQ ($ CAN '92) 1 s/m2 1 $ S23.W ' Rate of Application Labour %Rebmd Rock VisMity SetTùne 2.8 persom Dry: W& Poor D~Y s 2.8 persoris Dry: Wct: h r Day s Envitonmental Befm Use During Use ' - based on limited data
71 The data h m Table 10 has been fiuther r&ned using INCO costing information and time studies for bolting and sc~aning and for MimgwmP and shotaete liner applications (set Table 11)- The INCO cats fbr deveiopment ue hi*ra on an ara of covicrpge u wcll as for a linear fbotage of advance, for cornparison of the support opiions. It is asumed that the costing refers to a devebprnemt heading with support beig installeci in the back and upper walls (to within 1.5 m of the floor or base of mil (BûR)). It must also be mted that the costing data is dependart on a number of other fjbdors such as: equipment used, shift schedules, paformances of cmaq dn'ft mwd Iengtb maintenance, number of adive headings, trarnming distances, set-up and teardown requirements etc. For simplification and direct cornparison betw;een different types of support, it is assumed thaî the bolting-and-screening is achieveû using a scissor-lift truck with hand-heid stoperdjack-leg drills. The MineguardN application is achieved using a hand-operated spray-gun and the industrial pumping/mùting equipment while the shotcrete is alsa applied manually with dry-rnix rnachiiery (both liners assume stand-atone support, i.e, no bolts). Labour and equipment maintenance costs are included in the cost per metre of advance. Al1 other input information, such as the loadiig and mucking quipment, is kept constant as well as the tramming distances, incentives, performance ratings, and shift schedules. The development heading is assumed to be a standard sized opening (4.9 m by 4.9 m.) with 3.7m drillecl rounds achieving 3 m advance breakage. Using this input data, the summarized costs are listed in the following Table 11. NOTE: The data in Table 11 does include costs associated with some intangible items, such as: (1) shafk downtime for matmal transportation, (2) accidents associated with support installation, (3) accidents associated with inad- support capacities, (4) potential rehabilitation costs due to poor support perfomÿuice/life, (5) production loses due to poor support performance, and (6) schaduling delays associateci with possible addii environmental constraims during liner applications (is. headings isolated due to i v e s with MineguarbTM spraying or due to excessive dust generated with dry-mix shotaete).
72 Table 11. Summary of support considcratiom at INCO Limited (1998 data) MattnalCosts Ymofadvancc $2'71.16 $ (S CAN, 1998) um2 531.n sm.84 Rate of &/min O. 138 O, 124 Application $ The cost of ground support insullation is gnrtly influed by the equipment with which the support is installeci or applied, as weli as the experience of the crews. In fkct, if a remota controiled application is used in place of the manuaily-operated equipment, the rate of application Uicreases s~b~ally. For instance, the fernote application of steel-fibre reinforcd (wet) shotaete at INCO's Stobie Mine is achieved at a rate of m'/min, Assuming a shotaete linet thickness of Sem, the rate of application d l be equivalent to m'/min. [Graœ, pers. commua, This application fate has been achieved at Stobie M. foliowing several years of trouble-shooting of the mix-blend and with the opemîors' experïence. New automatic spray sysiems indiate potential of 0.2 m'/min for shotcrete [Runciman, pers. commun, 1999J. In a sirnilar fàshion, remotmmntroued equipment for MineguararrC offers produdvity improvements. An application was tested at NO'S Research Muie in April 1998 and the rate (ahhough for a limiteci spray duraiion and area) was slightly in& remoteix,ntroued application rate fbr as compared to the manuai procedure. It is belid that the cen be fiuther aihanced with operator- farniliarity with the contn,ls and with wmpletely automateci equipment in the hue.
73 The pcochlctivity achievcmcnts asmciated with various rnining methods (Ia alone gound support systexns) have long bœn a debate in die minhg uidustryuidustry Of course, this is fiirtha cornplicated with the naed fw profitability - as opposad to direct produaivity. In a mining operati~~itise~~e~tordi*vequaütyprodu~rthathpij~aproduaimitsee Thac is a distinction betwœn ore and wastc and, obviously, this translates urto pro6tability or mt. To ensure a viable future, udegmd mines mus& "tmploy the eumomies of high quality production, not the -mies of Iaqpscale pnibction" ~ O S& S Morrison, This whole proddvity debate is not easily resolved, due to the comptity of the mining operations. Invariably, pmdudvity and econornics are linked band-ikhand, which are a d i muitant of ail the activities of an entire mine. Unfiortunately, mining is a dynamic system that changes fiom moment to moment, hencc an WdctStanding of the produdivity and economics at one point Ui the will mt necessanly rdect the o d situation for the life of an operaîion. Furthenm,re, the wst-structure itself is not straightf- with costs distributed across oblique activities. The wsts becorne even more cornplex when considering the other operating plants, such as the mills, srnehem and refinaies, within a large COIPOC8fion. For aiment emnornic evaiuations, a holistic apprd cen be takm to understand the benefits of rnining methods, ore grade rccovaies, technologies, etc. venzie & Doggett, A range of cash flow and discounted cash flow aiteria can be utilized to assess a mining operaîion on a before-tax or total economic potential. Probabilistic risk analysis can also be perforrned, to gain an understanding of the probability of the downside risk and the upside potential. This type of holistic economic analysis requires a clear delineation of a mine p b complete 4th estimates of (1) capital expenditures, (2) operathg cost estimates, (3) ore reserve estunations, (4) proqiction rates and schsdules, (5) net ore valtdom, and (6) estimates of fùture market values of the metals. Ahhough there are software progmns to perform the economic evaluations, the entire mine design process is manual and tirneintensive- Simplistic evaluations are a misnomer. The econornic evaluation of minerai deposits is an area of- whacby design options and duations need to be generated quickly and easily, using process emulatocs inttgrated with cconomic software and decisionmaking logic.
74 On a dla-de, thc pmdudvity a d d c s rcrocltsd with various gand suppcnt systems seern to be a more appniachrble subject to ddress. Howtvcl, it must k ncqnkd that a round-by-round dysis of a grourd support type wiil not incorporste any of the intangible items that dd coats to the Onginal poasspoass In partiailu, the support fiilurcs, the rehabiiitation cow the injuries during support insiailotion, and the cfféct of pm support performance on the produaion ratc, are incidents that are diftiaih to quantiq in tams of predictions and in terms of msts. In a cumparîson between and-^ systans versus a pdyurethpne IinersuppatS a qualitative approach of the ''probable" inaeesed ri& ofproduaivity kreases and associated costs has been estimated in the fouowing Tablell Table 12. Probable production interruptions and associated cost impact: support with bolting-and-dg vasus MineguarbY liner. Spray+n Thin Membrane 1) Greater probability of support darnage a. the fita of an active development heading, thedore: Increased small-scale rehabilitaîion wsts and need to -que =me bohs 2) Greater support tirne, thedore: Increased labour cost due to slower development rates 3) Greater probability of physid harm and installation accidents, therefore: haeased w.c.b.' fecs 4) Mote support components and equipment items required with proces, thdore; Increased costs assochted with delays for missing parts(etc. 5) Greater susceptiiility to corrosion, therefore: ùkxeased rehabilitaîion axts or need for secondary support with shotcrete 1) Greater probab'iity of support Mure (as a stand-done support product), thdore: B Inctegsed large-scale rehabilitation costs or inaeased need for a tw+pass =JPpo't wtem 2) Less ~gged equipment, thdore: > IncrePsed equip. niainterrance costs and mobilizatioddemobilizatiin tirne 3) Greater probability of material spoilage (quality contrd issue) therefore: B Increased waste &+or handling req.'s 4) Greater requimncnt for deaddry rock surface ditions, therefort: Incmscdcostforsurfàœpreparaton, and inaeased time for tirying- 5) Greater auqtibility to production flyrock damage, therefore: B h r e a d rehabilitation costs in bulk production environments
75 Standard spreadsheet calculatiolls do not d y allow fbr au of the mining ''rate and nsk factors" to be taken uito amsideratioii within an acanamic bnakdown- I3mcucr, new computer-based simulation toolq such as Auto- and Wmiess~Y, akw fbr this type of productivity analysis. Tbe diffèrent developrnenî 7 can be acauptely simulated in terrns of time, while the life-cycle of a drift, a stope, an ore body, a mine, or an entire mining Division can be analyzed with alternative development and production processes. The drift developmmt process is outiined as fouows, using aimnt pnaices: Ground support is mdly accomplished with hand-held equipment (stopers and jackleg drills), or with large machines, such as a MacLean Bolter. Current support ciesigns at INCO cal1 for mechanical or groutad bohs to be installeci through wdded-wirc saeg with typically 8 bolts instalied per 1.5 m x 3.5 m (5 A x Il fi) scrceri. A staggaad, diamond pattern is used for bolting: 1.3 m x 0.8 m (4 fi x 2.5 ft). The support is installed in every new round, to within 3 fi. of the fkce (or less). The wall support is generally also installed in the new round, dthough there are cases where the lower wall support is iagged behind the advancing fke. This exception is appropriate fôr saféty and produaivity reasons odyy Tk walls of the headuig are supporteci to within 1.5 m (5 ft) of the floor ter ail development hcadings, uniws ground codions dictaîe othenivise. A compkte guidehe fbr suppat instaiiation has been gerierated for INCO [Gnnuid Support Guidelines, INCO Ontario Division, 1991.
76 The INCO support guidcline is applicable to ail mines wrwr thc Ontario Division Changes hm the guidelint are Mequent since a complete Enginaaed Design misc be wmpleâed by the head-fiame Ground Coiibd En- Dependhg on the support - and rppovsd by the mine-site management- of a pprtiailu herding, the spray-on pdyurethane liners have the opportunity to fùkil r nimba ofroies within the developmenî pooess: 3. - as a screen replacement, wtiereby bok are installed immediately atter the limer has been applied- The installation rates associated with dif îî support des, and with different support systems, have been determuid 6iom viuious time-sbdies within INCO and 6wn contractor rateschedules. The ovd productivity of the development pnocess is then assesd, as a component within the entire muung opaation - the preferred support opion will yield the achievement of the highest profits to an operation Indicators of hi* profit options rnay be refleded in values obtained for, (1) the developrnent rate ( m e oufpcas), (2) fiice m o n, (3) eguipment utilization, (4) aew utilization, and (5) time aliocations (waiting the, process time, and minalife). AU indicatm must be dyzed together, to gain the neteffi of the pmasp option. Ahhough, the o d muielife is an indicrtor of timing for revenue gerieration - this usually has the highest impact on the economic rate of rem of an operation. Rudimentary simulation studies at INCO's Mines Research Department have demonstraîed the dramaîic effect of ushg spray-on liner support versus conventional boltingsnd-~cfeening bley & Yazici, These studies indiute that d e r wceu, to the m mne is achieved when using Liners for support, as cornparad to use of scfeenjilg-and-bolting systerns. In fact, the entire life of a mine (or minhg of a stope, or Mt, or ore zone, etc.) is comprcssed, allowing for higher net retirms to the mining corporation-
77 The ground support priobctivity dysis has ban achieved with a simulation software package called AutoModnr. SpeQficaüy, the poductrvrty.. gains associaied with different support systems are mmmrkd in Table 13. This chta watt takai h m mining simulations of NO'S 175 Orebody (the Reseuch Mine), 16th extradon of the South Pod ore =ne. The rnining was simulatai using a sblevtl retrest mining method, with m bacic6ll. A top-down mining quence was used, with stopes set at 30 m in height and 46 m on strike. A set of six ri% pillars, 12 m on strike length, were used for support aaoss the zone. Four rnining horizons were used, for a total of 19 stopes and 1-5 million tonnes of coppcr/nickel ore. For the given mine design, the two simulations were nm using NO'S DP Modei, (using the AutoMe software code), to compare conventional development using boit-and-screen support versus a liner support system The simulations used tk fouowing support crew and equipment: (1) one operator and a MecLean Bolter fbr the bolting-and-screenllig operation, and (2) one operator with a MEYCO Spraymobile for the MincguardN liner support system application. The devetopment process tirnes for the two support systems are: (1) 11.7 hours of actual f- the for the conventional bohs-and-screen scenario and (2) 8.1 hours of actual face tirne for the Min- support mdhod. When delays (due to personnel transpdon to and h m the work site, waiting the for parts etc.) are included in the cycle, two cornplde devclopment rounds are completed in 7 shifts (or 56 hou=) for blting and screening support. Using the sarne conventional methods of process wntroi, the Mineguardric support allows two rounds to be completed in 5 shiffs (or 40 hours). nierefore, the MkgumP enables the development to be compleâed in a shortcf tinie-fiame, and fbr the produaion to aiso bc COIK:W in compessed the, as compareci to the bolting and saeening support system.
78 For the mining of the South Pod ore zcme, the dimatai irnpovemenb in the development and proqaion times am Ui Table 13 (Le. fk the two SirnuiPtion studies of MineguardN versus boltd-screen support systems). Table 13. Simulation study to compare bolt-and-scteen support vs. liner support: conventional mining techniques for INCO's 175 OB WC0 Sim Team, Start of Development Boband-Scmeo Day#O MincsurdF"' Day # O ~iprwement 0% ' End of Development Day ft 895 Day # % S tart of Produdion Day # 209 Day# W End of Produdion Day # 1132 Day # % 1 Total ProductionTime Dayo Days 1 9.4% 1 For the simulation study, the rnining is completcd with an apptoximate 3-month advantage, when using a spray-on liner fbr support in development and in production access headings. The 3-month time translates into econornic benefits in the fom of dued overhead and direct-rnining costs, as weü as fàster generation of revenues with inmas& throughput of ore to the dl, smelter ad refineries. Som of the dired-mining and opaating cost items that would be afeécted by 8 shorta rnindife incide the ventilation and pumping systems, as weü as the labour and maintenance raquiremerits.
79 Production Procm For most rodeqpmâ producpion pmceswq a sjxaya lina has a Li& use. In parthilu at INCO Ltd., where the mjority of the u&rpund ore is removed with bulk-mining techniques, the spray-on suppofi wdd only be applicable to the support in the access headings and not for support within the stopes. In contrasf ait-and-fil1 Mning operations would require vast use of a spray-on Liner, for support of the access headigs and the stopes. The liner would be of particuiar use, as well, for codhment support of pst ad rib piflars. Xn the buk-stop accesa, wmmonly darad to as dl headim the dcwlopmcnt proccss is applicable. In most cases, sprayon Liners would be used to suppoct the access headigs, only for the duration of the stoping process. Mer mucking, the stope is gendy filled and abandoneci. In most cases, siil hdings are used for the mining of only two stopes - the one above and the one below the siil. Once these siopes are attraded, therc is no fùrther need to gain access into the sill, In cornparison with capital development head'mgs, the production access headings mate a different complication for sprayon support, i.e. refîerring to the capacity requirements of the liner. Most dl headings a INCO are within sulphide ore rock types, with the added influence of mining-induced stresses. In some cases, the stresses are inaeesed around the rnining silis, which would resuk in stress-inâuced slabbiig in the bock d waüs of the siil drifts. Conversely, the stresses rnay bacorne reduced (Wle), resultllig in the relaxhg and los of clamping around the sül hadig, which caild lead to the poid fôr fills of gramd with wedges or previously stress-hctud rock
80 In the case of mining the upper ud lowa stopes with a central siil horizon (i-t. uœng the si11 asatapsill~rthtlowastape,drsabottmsillfiktheuppastope~tht~inthe sill hdig will usuaily expaiaice a transition: hm the initiai fx-field conditiorrs, to high- stress, followed by t d relaxath at the ad of the midring cycle- The insiallad support rxnast have the capcity to support the rock throogbut the complete stress change. Some mines employ modifiedstrand cable bhs, in ddition to the stmdrrd support of rebar bolts-and- screen,tocopewith~changeschanges In the case of eïther high or low-stms Condjfions, the rde of standdone liner support would be iimited, ifnodstent, in siil headings- The lorduig arrangement in the sills would most likely require her-and-boltuig support - this may be nquid during the driving of the access heading, or at the very least, with the bohs installed just prior to stop blasting There are likely very few instances whae the stand-alone liner support wodd provide odequate protection and support of the sills throughout the entire mining phase. The spray-on ha provides support apacity thnnigh a tenacious dhcsion to the roclc and a very high tende s~rength to resist block movernents on the exawation surf%ce. Comparaîively, shot~dt (as a ddie support) provides some fiexural strength to resist bending- The rock loads are transmitted onto the shotaae üner, which acts in compression to resist the loading- Unlike the thin spray-on hers, the shotacie üner forms compression arch to support the back and 4 s ofthe excavation. Typically at INCO, seconalyy shotcrete support is used in the siil headings. This has a fold purpose: (1) for support of the Ming, as the dning-induced stresses pas h m hi& stress to relaxed, a d (2) fbr pmtcction of the bdt-ud-saaai aippolt during the VRM b l ~. It is comrnon to requirc substantid rehabilitation of a non-shotaeted VRM top siil du~g the production-blasting phase- The shotcreâe, though costiy, viwy eliminates the need to recondition the sill during produdion With widespread use of shotcrete at M O, many underground workers have b m e afnidomed to the pristine conditions of the shotueted sills. Th- is a question whaha this hi* ievel of support is now excessive.
81 Cut-and-Fill nliaing Applirltioar There are two cut-and-fil1 opatbns at INCO's ûntmb Division MUies: (1) pst pülar and (2) narrow vein, with a discussion of cach rnethod ud the rppücability of ushg spray-on liners for support in these produaioir saripnos. POSTPIZLQR CUT-&EïLLmG: Large-de pst-flar cut-ud-fill rnining is d y pdxmed at ont of INC07s OntMo Division mines, in the McCfsady Easî Main Zone. This mining rneuiod uses 9.2 m wide slots with a unique scaggasd pattern of6 m square poz~t piks [Espky et. al., I99q- The produdion cycle for the mechanized ad-an6611 mining method is veq similar to standard drifting, however the cfrilling l d i and aipporting activitia require two setyps with the wide (9.2 m to 9.8 m) slotsots OCherwise, the process fokws the same steps as the drift development process: cidi, I d & blast, muck and support A thin sprayon her could be used in the support adivity7 to replace the nead for scrccn, and to mentially allow for the expansion of the bolting pattem. Since there are few wedges within the partiailar ore zone at McCreedy East Mine, the sprayon liner support mua be designeci for two main loading conditions: (1) the high-stress conditions (Le. with stress slabbing) at the abutments and in the crown pillar, and (2) regional tende stresses in the stop back Wth bolhg and the sprayan liner7 the productivity in the mine may be eqded or improved, as compared to the surent bit-and-screen systm The application would require remote- controiled equipment. The 8conomic benefit of using the sprayon liner, therefore, would be the cost reduaion of bolting requirements Md the pot& production rate increase. A simulation study of the cut-ad-fil1 o pdon was complcted for the nww [Cohl, 1991, and the sprayen liner has shown an incrta~e in the pradudivity, as compared to bolts-end-screen- Another substantial bene& of ushg spt%y-on liners in the cut-and-fil1 environment is with the support ofthe post pillars. A continuous membrane ptovides pillar confinement and interlock
82 Specificaiiy, the support aprqty is dcansd equivaiait for thc two scmarios based on mnfi.nement: (1) the ber will waü dildon rnd will redw bss of capacity, while (2) the boit-and-sctan upport d l dbw the pillm to slowly siab and spru tlus reducing the &edive support ua to the cac of the pülar. This stsianent is ûue fpr cyluda piliars (square piilars & mt provide load-camyhg apocity ai thc canas). For the McCrsedy East Main Zone, the dded ae tccovery by reducing the post-piilar âiiensions to 4.8 rn by 4.8 m, fiom the onginai design of 6.0 m by 6.0 m, is quivalent to 3 to 6%. For a high-grade deposit, this equates to millions of dollars in added revienue. NARRO W ~ ~ G : The produdion-cycle for narrow nin cut-d-fil1 mining is more labour-intensive than standard development muùng and the largescale cut-and-till mining techniques (refer to Figure 4), with two mucking seps in the cycle: (1) drill, (2) load a d blast, (3) muck and condition the pile, (4) bolt and screen, and (5) final mu& Due to the MHOW nature ofore stringers, the siopes arc also very mow to mine dilution These narrow stopes quire specialid equipment, with low and narrow profiles. There has been no scissor-lia ûuck available for this environment; thus, the badc support is installed manuaily using had-kld drills. Afta drillhg ad blasting, a portion of the muck is lefi in the stope, as a conditionrd floor, in ads that the aippat crew an nsch the back with drills to instaii the boh-and-saeeri support. Once the back is supported, the remaining ore in the heading is removed. Foliowing thiq the wall bits and services are installe4 and then the cyde is repeated.
83 Figure 4. Mining cycle for narmw vein stopes [ Treen, The double-mucking pmcdure in Figure 4 U rsqumd for support installation This dded step causes an inxsse in cycle-tirne and a wnes~onding deaase in produdivity for the mw-vein stopesopes To the rnining cyd+ worth exploring is the elirninntion of the re-mu& ppccdun by rcduchg the dope hnght 0.e. instali support frnn the floor, raîher than h m the condionai muck pile), Figure 5. I - Drill I Figure 5. Mining cyde, 153 OB, stopes with reduced back heights [Treen,
84 The adaptation of the 2.3 m s!otopc haght mining-cycle with use of Mineguard" in place of bolts-and-screen is representcd in Filpue 6. The aippori poition of the cycle is achieved with a stand-dont Mintguardrrr application, which follows the rock prepdon procws of washing the rock surface. Figure 6. Mining cycle for narrow vein stopes, using MineguarV and reduced back heights [Trem, Intuitively, the rate of minhg can k inat.scd by using low back heights (2.1 m to 2.4 m) and an alternative support to bdtaand-screen, sudi as the StMdalw Mineguarfl liner suppt. The actd productivity gains requin fiinha dysiq to aisurr the stop geometry d use of MineguardTM will provide a produdivity increase and reduced cos& A preliminary adysis ofthc cut-and-fil1 mining mehd was cornplaed for the 153 Orebody, using the mine simulation tool, AutoMn The data of the pduaivity gainsclosses essociated with altaing the stoping cycle and gecmeüies indicated a slightiy longer mine-life with the smaller ait heighy evcn with dw use ofrapid setting spray-on liners. The simulation analysis indicated that the higher ait-heights, even with a more amplicated production cycle, yielded the preferred rnining option, hm an &aiomic and pductivity point-of-vew.
85 The vision of current research at INCO Limiteci is to develop new techniques to meet strategic objectives, one of which is to increase the productivity in the mines by at least 20% through the introduction of reliable equipment automation, For this to becorne reaiity, the production and development cycles have been scmtinized to find ways to cornpress the tirne to complete each tsisk andor to diow for new processes that result in impmved productivity. Historically, only technologicai impmvernents (either by changed mining method-s or through rnechanization) have led to ~ i ~ c a productivity n t improvements in the mining industry, Figure 7 Baiden, Ontario Division - Mining ProductMty I Figure 7. Productivity trends for NCO 1998) Since the rnid-1980*s, there have been quality improvements in the mining process dong with some general improvements to the equipment, However, these changes have made srnail impacts on the bottom iine in productivity and costs. As such, mining costs continue to mount, especiaily for exploitation of deep ore zones, while metai prices slide. This has led lnco Ltd. into fuii-scale research of auto- mining systems - ted tefemining. This advance takes the remote-control proçess, Figure 8, hm the underground headings, to a control room on surface, Figure 9,
86 Figure 8. Remotetontrol of equipment from an underground station Figure 9. Remote-control of underground equipment h m surface control rwm Currentiy, with unease in the global economic market and the mining industry in general. there is full justification to pursue techno10gicai advancements since these "have a very important impact on the ability of miniag companies to produce at cornpetitive prices".
87 Furthermore, mining h dynunic and "technical ad production innovations wiu drive the ecommic survivai of the over the iipd two deadcs woss & Manison, One spdic tednologial advancc king ammineû at MC0 ir telefernote mining Telemïning, itself, is defincd as the long chtancc ranote control of mining equipment, using operations software, control mom concepts, tdecornmunications system and the mining machinery that can intaact with the temotely-locstsd operritor (see above Figure 9). The bottom-line gain 6om telemihg is the d for fewer ernployes to conduct the sarne amount of work Paiden, There is an o v d belief that reducing personnel 4 t h the mïnïng organization witi jeopardize the economic Mth of various communities across Carda, with fewer individuais directly empioyed with any given mining company. This beliec however, is a fàlse impression Stuclies have Udicated that pductivity improvements may result in the downsizuig of companies, but the overail uncmployment rate itself is dm reduced. Thiq at first glance, appears to k a connadiction However, the need for higher levels of automation and promidivity improvement has ld to the d o n of rnany more high-tech companies anci job opporûinïties [Globe & Mil, Nov In faq to remah globally successfiil, the Canadian mining indusûy must strive to achieve productivity improvements and should investigate ways to optimize the mining processes with a reduced wodcfiorce. Historically, the metal rnining indusüy is cyclical in nature, with &MOUS up and downtrends in metal prices. However, another trend thaî is les obvious is the constant drop in meta1 values, since the turn ofthe century -de & Dogge#, Even though the world's reserves of rninerals are king reduced through exploitation, the costs for mining and processing these metals has also been steadily decreasing - primarily due to technological advances. Furthermore, the rnining inmistry "hs cxpanded globiilly as various couniries have modified theu policy on natural ~~SOUTCC devtlopment and foreign ownership" Nos & Morrison, As such, new large mineral discoveries in previously-considered hostile environments or impractical locations have played a part in reducing the price of metals around the world,
88 Over the last decade, the mining industry has scai a dramatic drop in the pria of nickel and copper while the Mning costs in NO& Ma are rishg or wihut nnv sigdhnt advances in technolagy). With the aimnt udeqpd mining methods, there is an obvious point in the when mûs will a c d t~venues. To ovacrwne this evenatality, teleremte minuig offers a rmam to hprovt gcnaatc tevenues, and shorten mine lives. These benefits are achieved by improving: (1) pmdudvity7 (2) aew anci equipment ritilimtion, (3) the work environment, (4) the quality of work and (5) the cycle tirnes, [Baiden, There is another ben& fm teiemining, der than ensuring the sbort-term sustemme of the rnining operations Telemining ensures the long-tenn Survivability of a corporation and a mining cornmunity. in fàct, traditional methods of mining guarante that low-grade deposits near surfkce ate unecornimical due to the cost for rnining However, ifcosts can be reduced, these improbable rnineralized resetves become viable ore zones. It is clear that ".., the introduction of modem computer-bssed mining machinery.. offixs techniques to provide significant changes in the produdivity ud COS ofthe production of ore. Indeed, they offer the abil* to change the vay nature of what ore The ôackbone of the automation effort is the communication systern In addition, the other necessary technologies and process capabilities of telemining are: (1) navigation and positionhg (2) pnicess control, (3) delineation, (4) development, (5) production, (6) materials handling, and (7) enghedng & planning. The down-stream ore processing (milling, smelting and refig) mus& be scomined too, in an effort to eutomate and conîml those systems. From a ground suppon aspect, the development of excavations using automation techniques d l have distinct admntages, corn& to airrent rneâhods. The drifts will be devetoped with greater accuracy* in ternis of beiig on-line, on-grade and on-size, relative to the design. It is also azpected that the &&y will impnwe, with properly designed and developed headings, with less over-break and damage to the tammdiig rockmass. in fkt, it is more than likely that less support wiii be requinxi for the -ity of the excavations since the level of rockmass damage will be reduced around the excavation periphery with beüer blast control-
89 The productivity for teltaevelopmmt has the poteabl to be two to three times lasier thsn aurrnt rates, due to P longer worlmg time per shift and continwus operations thmughoiit each workday paiden, The rcbul utilizaîion of mscbllray and active headhgs will be in& with the patenbl fw 1WA pilductivity improvemenf~ thrwgh the usc of (1) muitiple machines and one opmitor, and (2) having rccess to multiple adive kadhgsûvdl the developmcnt ofthe hadiigs d l k more coordinated anci synckonized. The key to fistex development rites hingcs, as weu, on the type of support haî is used. New spray-on liners offa the paa*pr to dnmitially impve tht cyck tirne by behg rap* deployable products. Each 3.6 m round of advance will quire kss than 15 minutes for the application and setvp tirne of a pdyudme liner, using eaher manuaily operateci or automated spray equipment. In mmparison, ôoltless shotaete quires approximatdy the same spray tirne as polyurethane üna (Le. applying shotaete with new remoteumtmlled or autornated machinexy) but shot~fde Rquirrs typidy 8 hairs of set-up time, a more, More re-entxy is safie for workers. Of course, this becornes a ma* point Ui an automated Nne, where there am no personnel which caild be arposed to young shotcrde strengths. In faa a heading could be re-entered shortly afk the shotcrete application since the liner will supply a certain level of support for the utormted machinay. Only the effi of blasting on the integrity of early-strength shotcrete liners may require mher research The remote-controlled nature of tdemining offas distinct advantages associated with no personnel undergnwind. For instance, the need foe clearing the hesdings of personnel and for posting guards 6.e. before Md &a blasting) is no longer an issue. This allows for tele- controiled blasting to take place at any the during the shir Furthamore, the sufice control room dows for longer productive hours to be d e d ach shi& since there is no requirement for workers to travel to the underground work sites. The need for advancing semces is another activity thatt b6ts hm tdemining (Le. 60 m of able etc. requires about 5.5 hours to be installed conventionally, whik this tasic can be cornplad off-line in telernining). As well, the ventilstion requirernents at the fh do nat nrd to be as süingent for manless mines. This aüows vent tubiig to be inst.ned mon efiïciently. For instance, a long length of drift couid have the senices installeci in-tandem with drillhg at the h.
90 A summary of the advantages of tckmining for devebpment is indicated in the fobwing Table 14. r Table 14. Cornparison of conventiod and teleremote development proçess AW=t Coavmtionrl Tdcriemote SM Heurs 5hrs/shiff 7.5 hrs / shift AdvanœServias 5.5 hrs off-iine activity 1 Blastuig Times 1 e v a ~ 4 b 1 Any tirne There is another bfit to tdemining concenllng the timing for initiation of new mining aaivities during a shift. C d y with conventional mining, a miner or a aew wili not begui a new subprcess or adivity unless there is sufficient tirne remaining in the shift. This rneans that there is much lost time at the end of shifts, which d d be in the order of 1 to 2 holus for each miner or aew. The touowing Table 15 dehes the amount of tirne thai is generally requited befbre a miner (a uew) will begin a new activity. The timing requirements can be compared for conventional va-sus telemining situations. Table 15. Cornparison between wnventional versus telemining development: tirne requirements for starting a new mining activity [Espley & Yazici, I 1 - Drilling 1.O hr 5 min m g 2.0 hrs 5 min Mucking 1.0 hr 5 min For a h d i sized 4.8 m by 4.8 m, the total the to develop a 3.6 rn advance round, using conventional rnining methods, is eslunateci at 11.7 hours, with the the distribution (Figure 10).
91 4ucking. Support = 3.8 hn. 1.8 hrs. vice = 0.8 '3 hm. Drill = 0.67 ha. Figure 10. Development cycle, process thes, using conventional mining methods For the same size heading, the total time to develop a round using tele-remote mining methods is estimated at 8.0 hours. It is assumed that a spray-on ber, such as Mineguardm is used for support. The the-distribution is show in Figure 1 1, with a 30% improvement in cycle-the, as compareci to conventional methods. - -Cr. Suppor: = 15 hrs. F. '-Face Prep- = O hrs. Figure 1 1. Development cycle, process times, using tele-remote mining methods
92 One of the important ad- with Utomrtiai is the lrdr of pasorne1 in the headiings. This has not yet been accomplished on a widc-sale in any intemationai minhg company. To date, that have oniy bem d l tcas ofitoompion (within designated areas or with a mail sample of stopes, fm ktance).cirw, the indurtry. 'Fhaâae, a major challenge is to operate an entire mine with "undagnwd mobik whines [operasing] h m adkas, with the pot& to ducc signxantiy the n d for hmvn involvement in undagraud operations." [vagenas d al., 1997J. Once the technology has evotved to a point w)iae machines can easily be COnboUed fiom a afk control mm, the design CnteTi8 fw tht mine wiil change dramatically. For instance, the automated mine, without undergnwnd personnel, "wiu change the needs for ventilation, heaîing or amhg of air, ground support and infiastnidure'' Pagenas et. al., SpeciGdy, the s h of opcnings can hm srnaller, since these is m need to dow addiional tunnel width as a safity clearance between on-foot workers and machinery. Furthermore, the design of devcioprnent hadi will be geared to the local ground conditions, rather than imposing a cotlserv8tive blanket support policy. Indeed, the gniund support may be dcsigned with a fbtor of dety close to one, whereby a failwe in the roclonass would notjer,pardii the safèty of rny underground waker. Wth automated and manless mining, for the fkst tirne, it is now possible to design the support system with a higher h l of risk than waild normdy be accepte& Historically, the support systems and standard procedures have been developed for the worst-case situation and for manned headings. More over, this consernitive support design is then applied to dl mining areas, regardles of rockmas conditions, stress levelq use of the exc8vatio~ anticipated roc)rmass changes due to mining, etc. Furthemore, additional support is generally calleci for during the development of tunnels at depth or in seismicaily-active areas. A more redistic approach to support design waild be one based on the structural aspects of the rockmass versus the stress attributes. This would allow for the uphnt support of most headings to be accomplished quiddy, with only a need to pted against struciurplly-controlled fàilwes.
93 As the mining is king priepareci to commence, the close-proximity headings (Le. within 30 rn of a stop boundary) can be fuaher enhmced with additionai support, to guard against the rnining-induced stress changes and potential saess-related ground failures. This rationale ensures "a more concertai effort [is]... made, to incoprate support considerations into the initial mine design, to mininiize adverse effects." woney & Kaiser, 1997 Recent research into INCO's current support guidelines has been completed by the Geomechanics Research Centre (GRC) at Laurentian University. The study indicates that there is considerable economic benefit in rationalizing support installation, in order CO increase the rate of advance for development woney & Kaiser, 1997$ Specifically, developrnent advance rates could be improved as much as 3W0, compared to current development rates, if the finai, long-term support is rescheduled as an off-line task. In this case, the ground support is installed at a later date, while another activity is underway at the face - this allows two activities to be completed in the same the-fi-ame. Altematively, the long-tem support installation coutd be delayed, to ailow for support of a longer drift length (ive. afier two or more rounds have alseady been advanced and supported with adequate spmy-on "protection"). Table 16 indicates a =design of the development proces, to ailow 30% faster advance rates. Table 16. Current developrnent process versus re-design [Maioney & Kaiser, Shift#: 1 Current INCOSystem: 1 Re-Designeci Pc<)ress: 1
94 The GRC shdy nned th the short- support requirements fa most devebpment headings in the Sudbury-basin mines range hm: (1) no support, to (2) the complete system of shotaele liningr with syritenirtic boiting- Furthermore, an advancing drift head'mg often needs only -ma1 iupport untii the tume1 is ïmp.ctcd by minirig.ctivity. The grand suppoa is initiilly only rcquid to povide ptoteaion fiom MIS or bose. Other n ndi by Maioney a d Kaiser [lm indicaîe that there is much ment in designhg more appropriate support syri.ms for the dewelopment headings, Mead of using one consenrative design The neeû fbr engineered support designs is esgeciatly important, suice the support camponait ofdrifüng rrp~dp 35 to 45% ofthe cycietime. Reducing this tirne component wouid be the most e8;cctive means of inacpsing the o v d advance rates of drifting. To d eve this goal, supporting aunds in a just-htime iàshion allows for one means of ùicreasing the initiai advance rate. An additionai me- of rate increase includes utilization of rapidly-deployable support liners. W& this sgmd objective in min4 sevd underground trials have beai initiated at INCO Ltd and other rnining compnia ova the last decade, to test the effdveness of polyurethane liner support systems. Mng the trials at INCO Lunited, the occupationd health and safi issues have km examined dong with flunmability of polyurethane Liners and the dennition of thin-membrane support rnechanism, load capacity a d pfactical applications. These items are discussed in the foliowing chapters.
95 Since the d y 1990's, field application trials using polyurdwe pund support produas have ben conduded at various mine sites in Cana& the following sites: Barrick Gold's Hok-McDermatt Mine in Kirldmd Lake, Ontario Noranda's Bousquet #1 Minc in Malartic, Quebec Falconbndge's Kidd Cr& Mine in Timmins, Oatprio The applications have taken place at Sudbury Neutrino Observatory at INCO's Creighton Mine in Sudbury, Ontario, Homestake Mining Company's Eskay Creek Mine in northern B.C., Westmin Resource's Myra FaHs Mine on Vancouver Island, B.C., Cogema Canada's CluELake Mine in Saskatchewan, and INCO Ltd.'s Ontario Division Mines in the Sudbucy District: Lower Coleman, McCreedy East, Crean Hill, Copper Cliff South, Copper Cliff North and Stobie Mine, and the 175 OB Research Test Site. Intemationally, polyurethane grwnd support has hem used at Western Mining's Jundion Mine in Kalgooriie, Western Austmlia This application was for the purposes of a test, with cornparisons between Mine- and a latex spray-on candidate, Everbon6M- The test took place in 1997, with third-party testing and analysis of the data [Finn et. al., A brief summary of application experiences at the Canadian mines is provideci in the following sections. As described by Archibald et al- [199q, MineguardTM was sprayed almg a 100 metre length of main drift at the Holt-McDennott Mine for the purpose of evaluating rates of installation and potential benefits to be achieved by airflow fiction reduction. Full coverage of both sidewalls and ba& was achieved in approximately five hours using a manual spray application
96 Ventilation dysis dong this limited of Coptbd drift did mt, however, yield indication of significant fiction loss impmvement The la& of fndional resisionce improvement wu judgcâ to mult âorn too Limiteci a length of mateci drift upon which to make precise pressure-bss mammnents- The fbllowing summary is hm Archibald et. al More tangible evidence of the long-term suppxt crprbiiities of Mineguard~ was dexnonstrated fiom spray trials at the Bousquet #1 Mine in Northn Quekc. A train Mage drift was supporteci with the Mineguardrw liner, in addiion to previously installed split set bolts, with occasional installations of stcapping on the walls. The ground conditions are considered to be sheared in nature, with many sub-vertical joints with vay close spacing (< 1 cm). The polyurethane liner was able to infiltrate exposai joints and cracks in the rocbnass to form a continuous membrane coverage. Ail existing idbtmcûm (pipes and water lines) were sprayed around without any dismption to the application nor with any noticeable ovaspray accumulation on the floor of the excavation, Visibility enhancement due to the highly reflective nature of the coating agent was immediately apparent. Years afta the Iiner installation, m recunditioning has been required although grand decenoration due to stress change was mt arpeaed in this region of the mine. Only one area of the drift experienced liner adhesion problems as a result of an influx of ground waters in this arq the liner peeled hm the bacjc, in o dned region only. Mer sites within the mine wae known to be subjeded to severe convergence effects due to high naturally-ocauring and mine-induced stresses. At one such site, where neither rockboit nor saeen support was provided, a 2 mm Minepardm surface layer dernonstrateci its unique capability to support graduaily converging, badly failed loose rock which ezùsted within the drift bock A mass of hiled rock, comprising fragments averaging lû-cm in length and ocaipying a volume approximatuig 0.5 m3, displaced downward 0.5 m h m the baclc This broken rock was support by the defonned MineguarP layer.
97 At other sites within the Bousquet #1 Mine, shear deformations of MineguaniTM coated cirift waiis were observed At these sites, coating layers did not resvict viewing of sheared rock surfxes and were observed to remain intact, thereby offering continuous support resistance throughout the process of shear deformation over distances up to 2.5 to 3.0 cm. Sunilar behaviour would not be anticipated for shotcrete or bolt-and-screen applications. One area of the mine was coated with 2 mm of Mineguardm, in an area of excessive deformation of thicker-slabs of rock as compared to the sheared zones. This area experienced some failure of the Liner, with npping of the coating. lkely due to the extensive de formation. The rock to Liner interface indicated excellent adhesion, Figure 12. Figure 12. Lac Minerai's Bousquet #1 Mine. MineguardTM Liner failure by ripping. photo Courtesy of A. Ibbitson]
98 Of partidar intaest wrr the application of poiyurrthuw in the und- air-teceiver chamber on 2800 Level(853 m dcph). The excavation hd dimensions: 48.8 m length, 7.9 m width,and3.0mhcigbt. ïh*ritewa~usedtoasseastheappücstionpocessontherock substrate and to determine der aprstioirpi issues aidi as (1) appücation rate, (2) thidrness of the d g,(3) amaunt of ovcrspray, (4) air quility maisurrments. The cippliation dso provided an to daamirr the infüling capaôilities of poiyurethane oostings with a jointed rocbnass. Results of the triai are summarind in Scction l.3.2.l. 1 ofthis thesis rrpat MineguarG has been applied in approximately 8 1ayers (each being 1-mm thidoiesi) ont0 the rock surîàce of the Sudbury Namino Oboervstory. This site, which is a vay large cavern excavation in rock, has been developed fkom the 6800 Level (2072-m depth) at INCO's Crrighton Mine. The MineguardTM is only being used as a radon barrier, for the entrapment of neutrinos within the central cyünda. The test work at Queen's MIROC) has indicated the &edjveness of the pdyurethane copting as a radon Mer [Archibald, Radon barris testing is d i d nirtha in Seciion of this report. 3.5 Horn- Mining Company, Esky Cmk Mime The foliowing infiormation is oautesy of T. Corbeü of Engineered Coatings Inc. [pemnal commun, In Octoba 1996, the main rarnp at the Eskay Creek Mine was spcayed with MineguanP, over an atca of 186 m2. The ha was sprayed 2-mm in thickness Ui a 3-hour time-me. As weü, a lugc re-mclck wash bay was sprayed with MineguarP, with 186 m2 coverage in 4 hours. The appücator reached the back fiom 4 t h a scoop bicket
99 A fnu otha.ras of the mine wae sjnayed with IMkparP to test its efectiveness at supporthg the extremly wct a d middy conditions- Normally ground support mists of split~steelstnppllrg,dshotaere. Wrth the lkhcgud application in the very wet areas, a wickïng technique (offen employed in the construction industry) was uscd to aid in fùnneüng grd water inflows away fkom the rock mrfh [Carey, pas. commun, lm. The wicking is made k m a g e f*. The fàbric is rollai up a d fbmed into drainpipe arrangements, to provide vertical channels forthegrwnd ailtcrtocdla~ d dninalongtherodrwaü to the excava!icm fbor, mthout building up pressure behind the impervious MineguarP liner- A ~ p a s applicaîion s of polyurrthane support was used with the wicking. The first application mences some strength loss (due to foaming where there is excess surha water on the rock). nie second coat provides more strength to the membrane. From all accounts, the wicking nrethod worked well at allowhg adhesion to fm and rernain intact between the liner and the rock. The two-pass liner system created a strong membrane coverage. In a recent fbilow-up conversation with mine operators, the rmp and wash bay area an reportedly d l in dlent condition Eskay Creek is an interesthg case study, with the mine site siaiated in a rernote location in the coast mountains of B.C. - appoximately 2900 kilometers north of Vanc~~ver. Since transportation of materials to the mine is costly, the polyurethane ground support is an extremely attractive alternative to shotcrete. Gedogicaily, the onbody is within a mud zone and the actuai underground operations are very close to surfàce, wiîh approximately 30 m of unconsolidated material acting as the crown pillar. The ground corditions are vay poor, with constant gound water inflow and fiequently Ocaimng muddy seams. Despite low &situ rocû srrngtls heavy wota inflows and the mud, the polyureihw liner provideci usefbi support in the areas that were tnaied.
100 This infion hm bccn povided court- of T. Corkg Engbeered Cortingr [pn. commun,, Myra Falls Mine is a base metal opedon located in B.C., Canada The mining is adually occmhg bentath the ocean floor, off the cuast of Vîancouver Island. In May 1997, numemus areas in the Myra Falls Mim were sprayed with a poiyumhpne ground support producf IMmgumP. Specifically, the liner was applied on main horizons: levels 18, 20, 24 ad tk 149 camp. A total ama of 3200 m2 was -y4 with a t he breskdown as: 38 hours fot all mobiiization and dernobilizatim of equipment with another 113 hours of actuai spraying time. In total, 42 drums of material were sprayed at thicknesses ranging h m 1.3 mm in the 18 level maintenance are* 2 mm dong 149 ramp and on the 20 level, and 2.5 mm on levcl24. Most ofthe work was vw high, requiring staging and mobile equipment platforms. The g r d conditions for the areas were widely variable, from very good gmund to areas that were excessively wet Furthamore, some areas were very poorly prepard for the applicaîion wtiereby the rock was heavily cuated with dust, diesel exhaust residue, etc. In the very wet areas, the Liner adhesion was p r and the liner actually peeled away fiom the mck The dirty rock areas were nat holding up well, either. The application contraaor condudeci a follow-up visit to the mine site in Odober of Al1 available sprayad areas appeared to be in very good condition at that time. The mostrecent contact with mine operators, Januacy 1999, reveaied that the sprayed maintenance area on 18 level was d l in good condition Som of the dher areas that were sprayed were inaccessible due to oompletc ground support fàilure, such as a cable bolt fàilure and collapse of a heading. A reoent publication indicates that the mine has temporarily shutdown due to dety concems associated with the dficult graud conditions Ipaily Commercial News, During this shutdown paiod, a major able bohing effort is undawzy dong with an extensive shotcretùig program.
101 This infonnafioclhasbeenprovidedcouitesyoft. Corbeaof~ed Gmthgs [pers. commun, T h e C ~ ~ m ilawniumopastionlosptcdin n c SIskdchewuL In 1998, the mint site t d the new pdyum-polyurahpne hybrid pobd, Rod<guud, as a radon berna d as a support poqa Research work by Queen's Uaivefsity [Archibaid, indicated the excelient ability of the Rockguard ha to Pd as a d on Mer. Thyssen Mining of cuid. Ltd coainrcd the testing fm Cogana, with spcaying of Ruckguardintwotcara* Thefintsite,asaground~~~ltrdte~,wasonthe lûûkvelinthe Lowa DP Cada MIUiok ioass headiig (3 m in width and 3.5 m in height). A distance of 12 m dong the excavation wu coated. Although the liner was king apptied propaly, the rodc was adcn~ively wauwrrd. Consequently, as sa^ as the Rockguard product hit the rodc surf& application. the rock would wmble and turn into a dust The mating did not work weü for this A second test was establishcd in the Upper DJ South aocess ramp, with a profile of 2.5 m wide by 3.5 m high The rodonur in this area WPP beyond the weathered mne of t- 1, and was typid of the waste iock. A don amtrol bukhead was aected across the drifi headïmg using a wden frame with balap and fkbrene nailed onto it. The druchire was sprayed with Rockguard with an ovairp of 10 cm dong the sumwiding rodc Bonding was excellent on di airaices except the roadway, which was composed of gravel. This could be ovacome by burying the burlap into the Boor, to prevent seepage of radon dong the base of the ôuudiepd. Overall, the test areas a! Cluff Lake were vay wet and with high hurnidity. The radon barria aspect was prova out but the support capability on the acessively weak rock was poor. Since 1992, MinegusrP support trials have been conducted by INCO Limited in some of the Ontario Division Mines. Figure 13 shows a mop ofthe Sudbury Basin, with the W o n of INCOYs opaatuig mines.
102 Figure 13. Map of the Sudbury Basin with the location of N O'S Ontario Division mines Spray-on liner trials were conducted at: Lower Coleman, McCreedy East, Crean Hill, Copper CLiff North, Copper Cliff South and Stobie mine sites, and at the Research Test Site, 175 Orebody. The spny-on liner trials, some perforrned in conjunction with shotcrete studies, were initially implemented to evaluate the potential for use of these forms of spray-on liners as replacements for conventional rockbolts andfor screen-and-bolt support-. Trial #1: hwer Coiemm Mine, =lot, Top Si The first underground trial of MineguardTM at INCO was conducted in the 2û-slot top si11 at the Lower Coleman Mine between 1993 and Slot was the top siii for a blasthole mining stope, which had the foiiowing dimensions: 45.7 m long, 9.1 m wide, and 24.8 m high.
103 The top si11 was developed to size: 6.1 rn by 4.6 m for the 45.7 m length of the panel. The objective of this trial was to determine whether the MheguardTM coating could effectively replace rockbolts andor screen in this selec ted underground heading. The geology and geometrîcai shape of the Lower Coleman Mine orebody is quite distinct from other mining operations at INCO. The orebody itself is flat lying and, in some respects, bowl shaped. The orebody averages 22.9 m in thickness over a suike Iength of 366 m with a maximum width of 274 m. The footwall rocks in the Lower Coleman area are comprised primarily of granite gneiss and breccia while the norh range norite is iess altered than those found dong the south side of the basin. Figure 14 is a plan of Lower Coleman Mine. Figure 14. Lower Coleman Mine, plan W O, Lower Coleman Mine, Three distinct sets of major jointing have been encountered tdate in and around the Lower Coleman orebody. These features can be grouped into the following categories: pre-event dykes and inclusions, postevent massive dykes, and pst-event sheared dykes and faults. In gened, two strong joint sets are encounted throughout Lower Coleman Mine: one sub- vertical set (WO, 353") and one sub-horizontal set (5". =O).
104 Extensive sûucturai rmpping ud joint ddptions at the test sites yieided an ovedl rockmass classification, Q (8arton, 19741, of12 forthe host rodcand 15 fbr the ore. Muior andverylocaütcdvlri.tionsinstnichirrappesrthroughoritthemne,udthutherodcquslity raîings are adjustecl W y with respect to the conditions encomtacd therein Wdhui the 20 Slot test site, the rock qurlity rating is very good, with very competent ore and host rock At a depth of 987 m, the stms h l s are mderate- For the MineguarcP tesîing, a preliminary design was formulated, using the available technid data hm MIROC on the Mine- produa [Espley et. ai., The test method airned at evaluating support systems in holding up a dead-weight load. A b case of bolting-and-dng was testing initially, fof cornpison to the ahetnative support systems (Le. liner with or without bolting). The test methodology is outlined in the following flow chart, Figure 15. Figure 15. Test methodology fiow chart
105 Referrhg to Figure 15, calculations indicated that the standard bolt-and-screen suppoa used at INCO's Lower Coleman Mine has the capacity to support a slab of rock with dimeosioos: 6.1 m by 3.7 m, with a thickness of 1.2 m. This capacity is based on a staggered bolting pattern of 0.76 m by 1.2 m., with 8 bolts instded per sheet of welded-wire mesh saeen (1.52 m by 3-35 m). or one bolt for every 0.9 m2. The actual bolt holding capacity is equivalent to 1 ton/# (10 to~eslm*). The underground test was designed to create a loose slab of rock in the back of a drift (20 Slot) to evaluate the installed support, which should have the capacity to support the ''demanci" fiom the loose slab. Initially, the test methodology for testing the effectiveness of the conventional bolting and screeniag system in supporthg a 1.2 m thick slab of rock was established as the basecase (i.e. the existing support system at NO). Using the sarne test procedure, the performance of the liner (with and without bolts) was assessed. The test arrangement çalled for the complete development of the 6.1 m wide by 4.6 m high top siil heading, Figure 16. Mineguardm would only be required for approximately 4 to 6 tests (C33.7 m in drift length) for an application over approximaiely 20 m of the sili. Mineguard on back and iolls Figure 16. Plan of 20-Slot with the location of the MineguardTM liner application
106 The standard INCO bolting pattern was used to support the back and walls of the heading, using point-anchor bolts with the 6-gauge screen. The DWIDAG bolts were used in the trial in order that the plates and nuts could be removed for the stand-done Liner testing scenario. At the entrance to the heading, the back was slashed down an additional 1.5 m, to create a hanging brow of 1.5 m. The heading. at the entrance, was 6.1 m while the remainder of the heading was 4.6 m in height. AU the testing of the support occurred in 3.7 m segments dong the back of the heading, starhg at the siil enûance. S pecificall y, east test was conducted at the bmw, within the hanging breast For each support scenario, secondary drilling and blasting was then conducted, on a roundby-round bais, whereby the outer profile of the hanging brow was completely drilled-off with primeter holes (each hole drilled approximately 0.3 m apart). A second set of preshear holes was drilled and loaded; these were holes dnlled vertically to intersect the toelocations of the horizontai pre-shear holes, see Figure Test Area -.-y: * q- ". h -. Back Area foc Additional Tests -".&',&& -- 7.:., - : Segments :.;*-CF; f Figure 17. Section of 20-dot top siil: schematic of testing arrangement Every dtemate perimeter hole was loaded with Tribte-2C penmeter blasting agent. The drilling pattem, the loading strategy, and the type of blasting product were designed to shear the rock between the perimeter holes to create the dead-weight load via a hanging slab of loose rock (with dimensions 6.1 m wide by 3.7 rn in length and 1.2 m in thickness).
107 The blasting was cadblly dcsigned and e x d to ensure minimal rock and gm,d support damage and melly, Initially, the bgsacue suppcrt system of bolts ad screen were tested with the blast design This test was repeatad to ensure the testhg technique was vaiid and that the blasting was not creating undue fetigue to the support system. Following the basacasc, the IMkgumP (with and without bolts) ww to be testeci. The aaual application of MineguPrP required that the walls and back of the top si11 be thoroughly washed dom As well, a drying phod was ailotted, to aisue th& the coating wdd adhere well to the rack surfke. The thui coating (3 to 6 mm) of MineguanP was applied to the back and walls for a linear distance of 18.2-m At the time of the application, the relative hurnidity in the mine was quite hi&, a. 8% RH. The application was fw with spraying of 762 m2 in 2.5 hours with an estimated material cos& of $50 per m2($ CAN, 1993). The a d application oornrnenced at the dead-end of the htading and retreated outward; the saeen was incrementaily ait away fiom around the bits ond plates &le the Mineguardnr was being applied to the rock surface. A vamiculite coating wu applied during a second pass of Mineguarb> to render the coating as firc-retardant for underground use. The performance of the ground support system was gauged af er each blast using visual observation and instrumentation monitoring. In ail, three tests of bolts-and-ween were conducted, followed by two tests of stand-alone MineguardfM, and one test of MineguarP and bolts. The details of uich of the tests are provided in Table 17. Table 1 7. Surnmary of testing in 20 dot, Lower Coleman Mine, 1993 pspley, Date: Te& Set-Up and Rtsults: 2.4-m point-anchor bolts installeci with ü6 SCteen pshear holes loaded & blasted with ET1 Trimrite-IIC product, in every third hole 1 two GMM's were instailed, with the amhors a& 2-4-m
108 GMM's mea~u~ed minimal downward displacements Set-Up: 8 pshear Mes wae re-med with the TrimritaZC product, with loading in every odia hole Rtsuhs: socne damage was incurred in the baclc of the W ng, with minimal amounts of material d ispld to the floor 8 both GMM's were damaged by the blast set-up: 2.4-m point-anchor bolts installed with #6 meen 8 pre-shear holes were loaded with ETI's Trinuite-IIC product, in evay other hole 8 two GMM's were instailed, with anchors at 2.4-m Resuhs: 8 pre-shearing and dead-weight loading was clearly evident ground support was not âamaged and supported the load GMM's were loosened by the blast -- - Developed the remainder of the top si m point-anchor bolts installed with #6 saeen while retreated fkom the drift end, the screen was systematically ait down fiom the bolts Sept. /93 advand into the heading, applying Mineguardrrc to the back and walls (approx 232 m2) for a dnfk length of 1û-m during retreat, rernoved al1 plates and nuts fiom the bolts sa-up: 8 MineguarP supporting the back and walls pre-shear holes were loaded & blasted with the Tnmrite- IIC produs with produd in every other M e two GMM's were installed in the back
109 Continue-... rffa the blast, patches ofminegniatdrrr wae cither peeled or blown-off the back along with some loose rock- &mage co~lcenftafed at boit colh and dong strong joint traces one GMM was loose der the blast; one GMM reccuded downward displacements -- - set-up: MineguarP supporting the back and walls pshear holes were loaded & blasted with the Trimrite IIC produci, with product in every other hole two GMM's were installed with anchors at 2-4-m Resuhs: after the blast, a thin slab (3.6-m x 1.2-m x -3-m thick) fell fiom the back, tearing the liner sanail sections of Mineguardry, at the collars of the bolt holes, were btown off 8 the GMM's were loose in the holes Nov. /93 m MineguarP supporthg the back and walls 2.4-m point-anchor bolts installed pre-shear holes were loaded & blasted with the Tnmrite- IIC product, with produa in evq der hole (using one+ less stick of Trirruite-IIC in the left side holes than the right side) two GMM's were installed in the back m a h the blast, there was less damage to the left side of the back than the right side, especially at the collars OC the bolt holes small -ions of MineguardCY, Pt the collars of the bolt holes, were peeled or blown-off the back with some loost a video of the blast was taken and blast monitoring was condudeci
110 The dynamic testing indicated that the Mineguardm did not perform weii with close- proximity blasting behind the impermeable liner. The generation of blast gases, although rninimized with the perimeter blast design, damaged the MineguardTM liner at some local sites. Specificaiiy, dong the surface traces of the rock mas joints and at the coiiars of the boit holes, s d sections of Mineguardm (appmximately 0.25 m square or les) and rock were violently dispiaced hm the back, Eig. 18 and Fig. 19 (where a slab was dispiaced). Note: Figure 18. Results of test #1- MineguardTM liner without rockbolts 1. Liner is missing at the collar locations dong the row of vertical perimeter hotes. 2. Liner is missing at the collar location of the GMM hole (in the centre of the blast). Note: Figure 19. Results of test #2 - Mineguardm Liner without rockbolts 1. Liner is missing at the collar locations dong the row of vertical perheter holes. 2. A thin nxk slab was displaceci h m the back (3.6 m x 1.2 m x 0.3 m thick).
111 The testing of Mineguardm and bolts indicated slightly betier resdts to the stand-alone iesting Figure 20 and Figure 2 1. Again, the blast gases creaied some failure. Figure 20. Top siil supportai Mineguardm and bol& - before the pre-shear blast Figure 2 1. MineguardTM and bol& - after the pre-shear blast with littie additional failure In the tests with the bolt-and-screen support, there was dso indications of damage due to biast gases, i.e. bagged and loose material was observed at the boit collar locations. Despite this dynamic blast damage, the trial demonstrated that Mineguarda performed at least as well as screen for the conditions tested.
112 As a teinilt of the trial, the following comments are pvided as gend conclusions: It was inconclusive wh& the pre-sheat perimeter blasting actually created a 1.2 m thick loose slab of rock auspcnded over the top sill. The g r 4 movtment amniton indicated some downward displacement; however, this may we11 bc explainai as anchor slippage during blasting- It is suspecteci that the explosive gases were trapped behind the impervious MineguarP liner causing sections of the liner to be blown fiom the bock Once the liner was displaced, loose chunks of the roclamss were unsupportecl and were fiee to fa11 as well, The bolt-and-screcn support su~ved the blasting better thon the MineguarP and this gave the impression that the bolt-and-screen support is superior to a liner system. However, the explosive gases can readily escape in the bolt-and-screen tests, as may not be the case with the liner. The MineguarP liner was applied easily and rapidly, and the adhesion to the rock surface was excellent. The matenal proved to be very tough and flexible. Due to the grainy nature of the massive sulphide ore, the liner could be readily peeled away fkom the rock surface fiut taking a thin coating of the sulphides with it). The tensile strength of the massive sulphides is very low and this raises a question of the applicability of applying the Mineguardriw liner in areas of high-grade ore. It is not the adhesion to the rock that is the concern - it is the lack of strength of the ore itself. From the tests, the Mineguarfl liner perfonned poorly as a stand-alone support system with slabby ground conditions and a flat back. Without arching effects, the liner was not capable of supponing a dead-weight load of a thin slab of ore (3-5 rn by 1.2 m by 0.3 m thickness) equivalent to approximately 4 tonnes. Due to the specific requirements associated with handling the Mineguarfl liquid components, there was some dificulty in transporting the materials to the work site.
113 As weu, during the rpraying, dl personnel in the vicinity were required to wear selfcontainal bmthing apparatus to prevent inhalation of Urbome irocyanates. As an additionai precaution, the application took place on an off-shiff with no additiod personnel Ui the mine (other than those directly involvd with the spnying). Mine-wide monitoring of the isocy~~lfes indicated levels that d e d remmmedd TW& but only at the application site. The level of MD1 dissipated rspidly with ncgligible or no traces of isocyanates at ail otha monitoring locations in the mine. The reflective quality of the Mineguard- the liner was excellent The visibility in the top siil was greatly danceci following the MineguarP application The additional coating of a vermiculite top-coat reduced the reflective nature somewhat. The of the triai, comparing conventionel support with the MineguarP ha support using dynamic testing, ended in April At the cornpldion ofthe dynamic tests, secondary testing of the lina in 20 slot, under static loading conditions, was mnducted The dimensions of the reniaining section of Iiner were 6.1 m x 6.1 m in the back of the heading and a 18.2 linear-mares on the walls. This data was confinneci by an underground survey at the site. Ground movement monitors (GMMs) were installed down the centre of the 20 slot top siil excavation, within areas supported with standard bolts-and-screen and in regions only supported with MineguafdTM and bits. ïhe GMM monitots were installeci using drill holes in the back of the heading and using standard mechanical bolts to anchor the rnonitors. The GMMs were installai in June 1994 and manual readings were taken on a weekly basis until the insburnents were bked-up to a data acquisition system- These instruments were used to determine the rocbnsss response, dong with support interadjon, before/during/after the production blasting cycle in the stop. In total, fwr GMUs were ided in the conventionally supportecl area and three additional GMMs were installed in the MkgwmP area, Figure 22.
114 Figure 22. Location of instrumentation in 20 dot (level plan) After the instrumentation was installeci, a second swey was done, to pick up the locations of bolts and GMM's. Also, a reference grid was painted ont0 the back and walls of the heading, as a means of accwately identifjing and doçwnenting the changes in the ground conditions and support performance over tirne. Video and stiii photograph y documentation was conducted periodicaiiy, to capture images of changes to the ground conditions, The other data that was accumulated during this empirical test stage included: (1) blast vibration monitoring, to record the levels of vibration influencing the 20-slot area and to relate any support/mck damage to possible vibration sources, (2) geological mapping, to define the structural information and wedge identification for the slot drift, and (3) convergence monitoring, to detemine the amount of inward deflection, if any is detectable. The walls of the 20 dot top siü (which were sprayed with MineguardTM) were ais0 observeci over time. Steel screen was installeci lwsely over the liner on the wails, using an expanded bolt pattern to mitrain any potentidy loose rock fragments-
115 Over tirne, the ground support in 20 slot top siil was exposed to gradua1 rockmas deterioration in the very humid mine (+88% RH.). For the most part, the ground conditions in the 20 slot test site remaineci stable under static stress conditions. There was only one detected change in the rockmas conditions where Mineguardm-and-bolts were providing support; this change may or rnay not have indicated that the MineguardTM- ad-bolt support performance was less than that of standard bolts-and-screen. Specifidy, a displacement of 6-mm occurred in the back of the slot in the Mineguardm area while there was no indicated displacements in the GMMs located in the bolt-and-screen region. This difference in rockmass disptacements may be due to poorer support performance of the Mineguardm, compared to screening. Or, altematively, the roclanass with the MineguardTM was likely more fkactured and more prone to looseaing îhan the rest of the heading (Le. due its proximity to the biasting hm the dynamic testing). In any event, the displacement reading was considered negligible for the size of the heading. The rockmass conditions under mining-induced stress changes provided a much ciearer distinction between bolt and screen versus Mineguardm and boit support performance. As well, a cornparison was made to areas that had no support installed. When some cut-and-fiil stop extraction took place (approximately 30 m West of the test site) the unsupported areas dong the walis of 20 slot experienced excessive slabbing, Figure 23. Figure 23. Excessive slabbing and spalling in the lower wails with no support
116 In another area supported with Mineguardm. the ground conditions remained completely unchanged, Figure 24. Figure 24. Damaged walls with bolt and screen support; no damage with Mineguardm liner support At the completion of the testing of the Minegu- liner, with cornparisons to conventional supporting systems, the requirement for another test (using only empiricai testing procedures) was considered- The key characteristics of Mineguardm were reviewed, with the positive aspects defmed as: (1) high tende strength (equivalent to reinforced shotc~te), (2) high application rates (1 85 mh), (3) low materials handling, (4) apparent excellent adhesion, (5) superior support performance of Mineguard-and-bolts compared to bolts-and-screen, and (6) the ability to achieve ultimate strength within a minute of application. The disadvantages (or need for further research) were defined as: (1) the vedculite topcoating, which reduces the productivity potential, (2) the isocyanates and the need to isolate the spray-site, (3) the support performance, without additional bolting. The positive attributes, ou tweighing the friture research issues, provided the incen tive to further pursue the liner's applicabiiity as a ground support material. XII short, there were two primary benefits of spray-on liners: the productivity potential was remadcable, and secondly, the ability to provide an instant support to protect personnel and equipment was undeniable. These two aspects provided the impenis to conduct another underground trial.
117 Results of the h t phase of testing in 20 dot, where the liner was subjected to dynamic loading conditions and some Limiteci empirical tests (Espley et. al., 1994). hdicated merit for further testing of the Miaeguardm liner to determine limitations and appropriate applications. Afier September 1994, the second INCO trial was subsequently conducted in the Lower Coleman Mine at a site locaied in the 19 dot top sa, adjacent to the first trial (20 slot), in a blasthole niining area, Figure 25. The top silis provide the access to the stopes that have dimensions of appmximately 45.7 m in length, 9.1 m in width, and 24.8 m in height. For this trial, the objectives were defïned as: (1) ushg Mineguardm as a replacement to screen in the back of the excavation and (2) using Minepardm to replace bolts-and-screen in the waüs of the heading. Figure 25. Plan of Lower Coleman Mine, blasthole top sills, 19 dot and 20 slot: indicating the location of the MineguardTM applications In 19 slot top sill, two test sites were establisbed: one section with only MineguatdTM support, and one area in the main M g where Mineguardm was supplexnented with rebar bolt support. The 2.4 m %bar bolts were installed on a staggered pattern (1.2 m by 0.76 m).
118 The sarne suite of instnimentaiion as was iastalled in 20 slot was repeated for 19 slot. Instruments included GMMs, surface convergence measurements, and videdphotographic display to monitor the performance of the Mheguardm liner system and the corresponding response of the rock LII~ISS to both the static conditions and subsequent mining conditions. No instrumentation was instaiied in the h t test area (i.e. stand-alone MineguardTM) since no personnel are permitted to work beneath unsupporteci ground and, at that the, Mineguardm was not proven as a stand-aione support system. For the stand-alone support area, only visual inspection was used to assess the behaviour of the MineguardTM over tirne. observed for signs of deterioration prior to and during mining of 20 dot, This area was Figure 26. Location of instrumentation in 19 slot test site - plan section In the main test site in the top siil, the back was supported with rebars-and-mineguardm while the waüs were supported with mechanical anchor bolts-and-mineguardm. In this area the Mineguardm with bol& was compared to the actual support system of screen and bol&. Two extensometers were installed in this area, one in the Mineguardm, one in the region with conventional blts and screen. The extensorneters were 6.1 m in length with anchors at 1.5 m, 3.05 m, 4.5 m, and 6.1 m. Three GM. were also installeci in this area with one GMM installeci in the bolt-and-screen area and two GMMs installeci in the bolts and MineguardTM region, Figure 26. AU the instruments were hooked-up to a data logger to register measurements hourly. A photo of the test site is show in Figure 27.
119 figure slot top siii supported in the back and walls with MineguardTM and bolts Screen was hung over the MineguardTM as a safety measure, in case the ber failed during the trial. Although not clear in Figure 27, the screen is not tight to the rock in the Mineguardm area so that deterioration (if any) wouid be noted by loose in the screen- Although the primary objective of the new trial was to assas the potential of the Minegudm liner as an alternative to current support practice, appropriate methods of transportation, materials handling and application of the material were also stuciied. These operational considerations were focused on kause of the isocyanates used in the polyurethane coating. The use of this product in the underground, confrned environment poses some challenges for handling, transporting, storing and appiying the product, for ensuring ail workers' health and safety requirements are upheld. Potentidy, the isocyanates couid pose a health hazard to humans, but only if humans are exposed without ventilation protection. However, once the Mineguardm chernicals have mixed, reacted and hardened, the isocyanaies are non-existent and the material is inert.
120 A portion of the undsen>und &hl at Lowa Coleman Mine ammtmkd on nvthodr of aisuring a aafè, IrcYnrA-he application in addition to testhg a poiaitll mahod to isolate and neutralize the aûûorne isocyanaîcs. As weü, the support xnecbanism ofthe thin liner has been acplored, to dcianane whc<ha the lins behaves wnünrty to a shotcrdc liner, a whether the infiitration and ghhg abil* ofminqump conbib*cs tothe uppoit nuistiai. * * The 19 slot test sitewaschwaibccauseofthetrpnsitiorifkom at#ay-sîak stress CO&ICMW inaepsed stm~~~ with blsst v i ï and amamion fiom mining. As well, QNie the mining of the 20 slot blrsthde Jtapc and the 19 slot stopc, the IbGqpmP luia was ecposed to fly-rock damage. The test de provideci an oppartunity to determine the liner's ability to fiom blasting fly-rock Furthermore, the top dl sites (trial #S, 19 slot and triai #1, 20 slot) have been subjected to inaeasingly higher levels of blast vibration fiom mining within that vicinity- Specincally, within 18.2 m of the sites, blasthoie stoping and uppers-retreat mining has taken place to the east, and ad-and-fil1 mining within 18.2 rn to the west. 19 slot top dl wu thai fiirrher effkctexi by the mining of 20 slot blasthole stop in mid to From the instrumentation data, the pedonnaclce ofthe support systems (with respect to the changing mining conditions) were monitored and analyzed on a continuous basis since instauption in 1994 until the final 19 slot stop blast in In $4 the 19 dot application has been of particular interest since the top siil was subjeded to high levels of blast vibration, conaission and fly-rock damage. When 20 slot pane1 was niined in advance ofthe 19 dot, the &kt of the stress re-disbibution into 19 dot was observed. As a resuit of the mining in 20 slot panei, the bolted-and-scteened sections dong 19 dot showed excessive rodanass darnage with slabbing and bssging of loose material. On the lowa walls. wke there was m support Uistall4 the rodcmass spalled and slabbed, as was the expaience with the previous triai in 20 slot. In awnparison, the regions of the top dl,wtiidi werr aupported by MineguarcP showed no visible signs of rock movement and no indication of damage or daerioration. Again, this was the same rodanajs and support response that was recorded for the 20 dot test.
121 Observations also indicafed th conditions with the stand-alone iiner were as gooci as the conventionaüy supported region. During production dnlling, there was a requirement to drill through the Mineguardm liner in some areas, to blast some ore in the rib piilar. The drill crews were impressed with the ability of the drill bit to "bite" into the liner, as opposed to the usual skidding that occurs when starting the drillkg on the bare rock surface. As such, the ability to accurately position the drill hole was improved with the Liner coating on the rock, as compared to having botts-and-screen or no support. Furthemore, the drill crews remarked on the excellent condition of the drill hole collars, where holes were drilled through the MineguardTM membrane,. Figure 28. The collars were easily maintained, without damage and spalling, even when cirihg into stress-fiactured rock. Figure 28. Intact drill hole collared through Mineguardm liner, Luwer Coleman Mine During 20 slot recovery, a small-sale rockburst (O. 1 M,,) occurred in the 19 slot top sill. In fact, seismic source aigorithms located the rockburst within 3 m of the Mineguardm- supported region, at the transition zone between the bolt and screen and the Mineguardm liner s upponed areas. Underground observations indicated moderate damage in the bol t and screen section. There was no damage to the MineguardTM area.
122 Wng the bulk stop bhst of the 19 dot panel, the brick of the top si11 was sevdy damaged in regions expaiencing boit-and-saeen support, whik the MineguarcP supportai region sbwed m Udiution of damage. In fm the drift arch profile was completely maintained afk the blast, brt only in areas whae MineguarP support was provideû fw the rock Thtoughorit the reniainder of the top sill, al1 scnea was completeiy npped hm the back and walls as a result of the blast concussion, and large areas dernonstd excessive peel-bdc of the rockmass in and around the bolt heads. Overail, as a support has trernendous potential for use in specific applications: the leslot trial at LowerCdemPn Mure indicated that the Iiner - to replace two-pas bolting and screening in dl Wi: to increase produdivity in support installation Ciom 1 m (3 ft) dom the shoulder to base of rail, - as a replacement for screen: to reduce rehabilitation neeâs, where screen is normally damageci in conventional-sized spans or development headings. Dependmg on rock mas jointing and stress-effects, the bolt pattern would be detennined for the long-term support requirements dong with MineguarP. addition to the support pafonnance testing, the 19 dot triai offd an opportunity to doarment operational considerations of using MineguarP whereby fùrther investigation or research is required. For Uistsnce, one of the problems encwntered with d i g MineguarP was the requirement for a specific storage temperature. According to the IIUUWfachirer, the chernicals must be mahtained above a tempaihae of 65 OF. Beiow this temperaaire, there is a risk thst the isocyanate chemiuls will start to aystallize, which can poientially p 4 the discharge holes in the spray-gun Plugging of the pin-holes in the node cruses improper mixing and a pootq~ity-l3-
123 Another perocivd probkm wkh using in the Eaibncd undalgocnd aiviroxunent is.ssoaldcd with the rmtezids hancilhg and application of the podua v, in its liquid fonn, is a twmmmponem system and the matàpl is d y ttansported in sets of 55-&Pllon (US) drums. Because one of the liquid components contains isocyanates (&ch is a designated and cuntfoued substance), special precautions must be taken to sbély tnmport the materjal to the u n d m site- The storage and application dso requins sped5c proccdurcs and protocols. The transportdon procedure thai was uscd for the trial was to seid the pairs of 55-gallon drums to the test sites by using only appropriate motorized vehicles, with one operator (wearing an organic-vapour mask). The draw back wah the handling mahod wu the water-dousing poadurr (for Ming possible chemical leaks duhg transportation). Of of most of the d o n and apparent negativity at the mine site siemzned hm a la& ofexpience and hiliarity mth the chernicals on the part of aü involved personnel- Sorne of the pmcedum used for the 19 dot trial are outlii as fouows: AI1 personnel invdved in transportation of the chemicals musr cany an or&anievapour mrsk in the -nt a spill occurs. The operator must k aware of and have an understand'mg of the MSDS doaunenu for both chernid substances. All workers in the spray site must Wear a niil-fke positive-pressure breathing apparatus during the application and for 30 minutes afk the sprayhg CePJed. During the application, and up to halfan-hour raa application, the spray site mut k cleared of ail excess personnel. The spray site wst k guard-railed off with a doubk barricade. The stonge areas for the drums of MineguarP must be double guard-raiied and posted with uacccu Jlowed only to aiahoiized personnel".
124 6, In the event o h spi& di persoiuiel in the immediate vicinity must re&eat upscream fiiomthesitefinadistanceofatteast30m 7. N~personndrnpermi#edintheshaffconveyancewiththt~dnims duringtraiuportrtion 8. The existing uuciliary ventilation systems mut k djusted to a d mum of 18,000 c h during applicrtion, 9. A timeweighted aveqge cxposure level for MD1 must nd be exceeded d d e the mafea 10. Only neaswy paso~u~cl involved in the application may bc underground &uing the application. In general, the application was trouble-fhe and similar to applying a thick paint using pressure pumps. INtially, the two fhemids were prrheated in the 55-gsllon (US) drums and thai the liquids were pumpad to the spray mde. The preheating phase was requited for essurance of a good readon d poiymcrïsation of the product. The chernicals were mixed as thq. were spfayed fiom the spray mzzle gun From the nozzle, the material was ejected at high pressures onm the rock b- At the trial sites, the liner was applied 3 to 5 mm thick to the rock s d h in the back and walls. The 19 dot application proved an opportune time to test a new hypothesis for contrr,uing the aihome isocyanates that are releaseû during spfaying - i.e. to use a water cwtah as a mechanism for water particles to neutralize the i~~cyanafes. A water autain, sunilar to those uscd for dust suppression for dry-shotcrete applications, was consmicted and operated at a distance of 30 m hm the emtfance to 19 slot The mer anîain mes a very fine mist across the heading into which airborne isocyanate particles collide and becorne neutralized. The MD1 monitoring indicates that the water airtain is an excellent Engimered Co-t method for isoloting the spray site. Further monitaring was recomrnended, both undergouncl end in a contmiled laboratory fàcility, to validate the water airtaui technique. Details of the MD1 Mng are containeci in Section 4 of this thesis.
125 3.83 Trial #3= bwer Cdenian Mine, #l! Slot, BoLtom Si A third MuieguaraTM trial was instigated at Lower Coleman Mine in the bottom siii of 19 slot. This site was sprayed with MineguardTM dong the wau of the heading ody, Figure 29. Figure 29. Plan of Lower Coleman Mine, 19 dot bottom siii, location of Mineguardnl The 19 dot bonom siii site was used to test the Liner as a replacement for screen and bol& in the lower w d, to eliminate the need for a second pass to install bolts and screen. Figure 30 shows the application of Mineguardrm in the wds of the siu heading. Figure 30. Application of MineguardTM in the lower wail of a siiî heading 104
126 Thelimrwastpplied inscptcmbcr 1994, atthesametimeasthe l9aiottop di application The site did not have any instrumentation Uistalfed for rocbnass doring. Oniy visual ObSerVBtions were mpde of the site to qualitativveiy sises the i in _ot#rdystate stress codions and with mining-uiduced stress changes. In acûdty, the mining of 20 slot rnii.9pa the bottom dl ana to b m e highly stressed- The Min- area showed no signs of detaioration &le the ritmainder of the hading apaiaiad the uaiil ocaimncc of bagging of lwse and slabbing aiong the lower 4 s. During subsequent muwig of 19 dot itself, a thin pillar was created along the sprayed waii, with a thickness of 3 m or iess. It was pedicted that the stresses would exceed the strerigth of the rock and the pillar/wbs( would fid gradually during the rnining [Thibodeau, pers. commun, The v i d absavations showed the superior performance of in Wing the pülar wail together during th* mining phase The Liner was able to retain the rodr mess material and hold the blocks together and prewnt unravelling failm. In fàct, at the time of the 19 slot stope blasting, the condition of the 19 dot bottom si11 wall was closely monitored- Only a very thin skin of waste rock was left in place along the wall of the bottom siil, showing thai MineguarP was valuable for this type of rib pillar support. Even with high levels of blast vibration and gas production, the si11 wall did not show signs ofsignificant damage durllig the 19 dot panel blasting. It was concluded that the explosive blast gases had many fi.ee-faces to vent to during the blast, and there was m undue pressure ~reafed on the MineguanP liner itself The ability for the blast gases to effedively vent and dissipate was the merit to this test amangement in cbmparison with the dead-weight lod test design in the 20 dot (Sec )
127 AnotherMinqpurdn trialwasestablishedin 1994atLowaCdanuiMine,withtbrrctest sitesbeingrpnycdattheumctimeinsepcmba: 19rlottopdl, 19dot~siil,dthe 3150 rampam. The3150Rmp amawrrsei&tcduatertfa~ua replacement for cabk bdts. The site is a large span intemdon that would d l y k ~~pportadwith6rncmient-groritadcrbkbohs. The ramp test site was usai to eygjuate three support systems in die large span (10 m): 1. apptied over 2.4 m min-gnnaed rebar bol& Md scaxm 2. Shotaete applied ova 2.4 m min-grauted rebat bohs and scroen m cenient-gmuted cable bits uistalled on a 2.1 m by 2.1 m pattern, with 2.4 m resikgroritedrebubdtsandsaeen This area was of addiiod interest because of the preserice of a fàult ruhg through the bdt ofthe excavation Other than this feature, the rockmass quality was very good, with strong jointhg forrning large wedges. At a depth of 1100 m, the stms regirne is moderate with Iittle over-stressing evident in the vicinity of the excavations. In the 3150 Access Ramp ttst site, two Total Earth Pressure Cells were installed, with one ceu installai behind the shdcrete Liner and the second cell installed behînd the MineguarP. These instruments were insialle4 first, to daamuie whether meaningfid read'mgs could be obtaùled with the Iiner systems. Other studies have successfiilly used the pressure ceils with stiff shotaete applications; however, it was wisure whether the MineguarP would be ste enough to prioduœ resistance to sudb loading and subsequent inaeased preswe within the celis. The s4cond refson, stemming fiom the wcccss of the firsf was to clillect loading data for the shotcrete snd the MineguardTW in orda to compare the lads beiig resisted by the tw diffèrent liner systems- Additional UisÉnmientation consisted of four GMMs in the shotcteted area and four GMMs in the Mineguardn' rcgion. The installation of al1 the instnimentation in 3150 Ramp was completed in d y 1995.
128 Since initiai applidon of MineguBfdnr in 1994, the ramp intersedion has shown m signs of rockmas movement or detaidon Although cabk bits are d l y installeci in these wide span opmings, the use of shorter resin-grout4d rebar bolts and MineguarP Coafings bas provcn to be sufticicnt fdr support of this arca None of the GMMs recorded rodonoss displacements and the pressm œlls did not indicote pressure changes. It is unsure whdha the pressure cells wae fiuictioning propedy or ifthe iower stiffiiess of the MuieguarP liner prevcnd pressure hm devebping at the rock to liner interface. It was obmed that the MneguarF Iiner rapidly becrune very dirty and the liner lost its refledive appeai. Aftcr months since the application, it kame very difficult to differentiate between the rock surfàcc and the MineguarP d g. The shotaffe was easily recognizablc, but only because the screen was mvered by the shotcmte layer. Observations of MineguarcP performance in the trial site have also indicaîed that supjxxt conditions generated using MkgmcP liners are as good or better than those of conventîonally suppoited regions. There was one noted problem with the mahg pettainkg to poor adhesion to the screen Specificaily, sestions of the liner can be easily peded off the sueen, with a fine layer of COCIOded material on the liner. Likely, the rust on the screen eràsted pior to the MineguarbN application whereby the adhesion between the liner and steel wire is poor- Despite this poor quality, the adhesion between the MineguardTW and the rock appwed to be vay good- Wrth high stresses developing et this site, as a result of muùng activity in 1995 and 19%, visual and insrnimentation monitoring has also been cornpleted- The results cldy demonstrated the ability of Mineguardrrw liners to retain the rocbiiass material, hold the rock bl& togeiha, and pevent unraveling-fype fkilures. W& its rapid cure capability, it is posnilated that MineguardN's support mechanism for retaining and holding the tockmass may additiodly strrngthai areas surrounding excavations, thereby pennitting the rodows to support &If. As a result of the Lower Coleman Mine tests (Le. in the top sills, the bottom si11 and the rarnp location), MineguarP starteci to be used in other INCO operasions and ~pluilsua(pandsupporicompnentudssa~iistniaiaiprod~d
129 Due to the success of earlier trials at Lower Coleman Mine, MineguardfM was sprayed on the walls of two top SUS (te& 21 cross-cut and 22 crosscut) on 3240 LieveL Figwe 31. The iiner was used to replace bolts and sneen in these headings for blasthole mining. Figure 3 1. Mineguardm applied at Lower Coleman Mine, lower waüs of 21 & 22 top siiis, to replace bolts and screen At aii INCO minhg operations, top sili wail support is installed to the flmr of the headings to protect workers frorn rock slough during the loading and blasting phase of extraction. The requirernent for fuil profile support creates a two-pas support system for most operations. Typically, the back and upper walls are supported on the fmt pas, with either a mechanized bolting machine or with hand-held jack-legs or stopers hm the back of a sçissor lift truck. A second pass is then required to install the bolts dong the lower wall using jack-leg or stoper drills, working hm the floor. In most cases, the lower w d support is installeci just pnor to the production cirihg phase. Depending on the extent of the top siil headings, this procas can take a great deal of the and may requk a number of crews over several shifts. Mineguardm poses a beneficial alternative to bolting-and-scrieening whereby the lower wdls cm be easily and quickly supported.
130 in February 19%, two test sites were selected for further use of Mineguardm: the wd!s of 21 and 22 cross-cut were to be sprayed with the MineguardTM producî.. However, just prior to the application, the mining personnel questioned the need for vermiculite topcoating. Immediate research was initiared by Mures Research to determine whether the vermiculite was mandatory, as a ire-retarding enhancement to the Liner. The resdts of research k m Queen's University indicated that the vermiculite top-mat could be eluninateci from the application process. A supplementaq document on hre tests for coatings with and without a vermiculite top-coating was provided to INCO for review [Archibalci, The testing results were accepted by Mines Research and were adopted in the INCO application procedures. The elirnination of the vemiiculite top-coat was an enormous improvement to the INCO support system, h m a cost and productivity viewpoint: the second-pas was eliminated and the marerial handling was reduced. Furthemore, the reflectivity within the headings was enhanced without any dulling from vermiculite dust. The actual application of the Mineguardfh' (without vermiculite) occurred in Mach During this spraying, the Lower Coleman Mine embarked upon a training program for the underground operators. This was the fmt step to implementation for INCO and for the mine site. Application specialist contractors were used to train the INCO personnel. One interesthg fact arose dunng the application of the fm of 22 cross-cut - bootleg holes were easiiy discemible beneath the thin liner, Figure 32, which is not the case for shotcrete. Figure 32. Identification of bootleg holes through the Mineguardm liner
131 In addition, it is clear to pick-up major sûuctd patterns and jointing with MineguardTM coatings, Figure 33. Figure 33. Easily discernible rockmass jointing with MÎneguardTM coating Air monito~g for air-borne MD1 was conducteci during the Minepardm applications in the top siils. There were two exceedances of the TWAEV (i.e. > parts per million); however, this only occurred in the spray site. AU MD1 levels were beiow TWAEV levels at ail locations downwind from the water curtains. The testing is described in more detd in Section 4 of this thesis document. Frorn a ground support performance assesment, the Mineguardm easily pmvided stability to the 22 and 21 cross-cut headings for the production drilling phase. However, during the blasting of the stopes, there were some areas of rockmass deterioration. Specifîcdy, a large slab of rock becarne dislodged hm the lower wall, with rippicg of a section of the Mineguardm liner, Figure 34. This loose was estimted to have dimensions of 1 m by 1 m. and was 5 cm thick. The mechanisin for the failure is unknown; there may have been damage caused by drilling of some production holes into the walls of the pillars. This failure occurred later in the stope M e and was not critical enough to warrant rehabilitiition with bolts and scrieen. As with standard support systems, locaiized damage to the support is known to occus h m tirne to time in the blasthole stoping operations.
132 Figure 34. Ripped Mineguard~ on the waii of the 22 crosscut 38.6 Triai #j6= McCrieedy East Mine, Miin Ramp The main ramp hm Lower Coleman Mine to the adjacent McCreedy East mining operation is a permanent excavation, severai thousand feet in length and large in section: 10 rn by 10 m. Electric #ton Kiruna tnicks haul the muck and development rock hm the McCreedy East Mine to the crusher at Lower Coleman Mine. The trucks on this ramp sysrem travel at relatively high speed, therefore the mad-bed matenal is of high quality for eficiency and longevity. From a practicality and economic standpoint. the need to maintain continuous and high production with the Kinina trucks is paramount. This impiies, then, that the excavation itself must lx maintaineci in good condition, with no loose and slabbing to cause obstacles or to damage tires on the Kiruna tmcks.
133 For the most part, the rockmass dong the ramp is generally very competent, with the occasionai region of advene jointing. These areas, where there was potential for wd slabbing, were identifid by the mine site persorne1 for additional support to be installed. As an alternative to bolting and screening, the Mineguardm liner was seen as a more costeffective solution for lower wali support, from the standpoint of providing a fat application. Specifically, the sprayan Liner application could be conducted rapidly on graveyard shi fu wiihout interfering with production during day- and aftemoon-shifts. The bolting and screening option, whife Iess expensive than Mineguard" (for materials and instdlation). involved more shih and potentially more interference with the production SC hedules. Mineguardmf was apptied to the lower walls dong a section of the main nrnp during the summer shut-down pend in 19%. This work was achieved using second-hand spray equipment and inexperienced crews, with unfortunaie resuits. The mixing of the two chernical components was not maintained at the specified one-to-one ratio. This caused streaking of the coating (Figure 35)- p r adhesion and foaming of the liner (Figure 36). In addition, the liner was very tacky to the touch in cettain areas and very weak and crumbly in others. Figure 35. Streaking of the coating. Figure 36. Foaming of ISO-rich material. Due to the poor quality of the Liner, a complete assessrnent of the application was undertaken by Mines Research. Application specialists and repce~entatives from the manu hcturi ng Company attended INCO persorne1 underground to review the liner.
134 The with the application was an offd mixing of the prùripd compwdc. The comments regadhg off& mixing arc aimmuucd as fmows: 3. Wah the off-ratio podud on the substmte, the ISOrich areas pi& up moishm h m theairdstmttofosm,thenittumsaunchy. nieresin4chareawülst.y~ and SC& diowing dust fkom the mine to collect on its stdks. This trial has highlighted the extrerne importuia of quality contrd of the application Experienced nozzle-0~01~ are required and equipment maintenance is important Furthermore, it kcame apparent that a mechodology for testhg the in-situ liner is required, with dennitive proccdirrs and pmtocols, and a trouble-shooiuig guide for applicators. As well, equipment modincations are recommended, to ensure one-txwne mwng end propex chernid tempnhirro are maintained thmughout the application The fis& sienifiunt application of Mineguardrw over sueen (and bolts) wu undertaken at INC07s C m Hill Mine. This wu an application where Mineguardrw was used ta replace shotcrete. The projed was spearheaded by the M d s General Foreman, M. VanderhoOtt, who was involved in testing at the Lower Cdeman top dl,bottom siil and romp locations. In November 1996, the garage on 3800 Level at C m Hill Mine was sprayed with Mineguard'W (Figure 37) in order to provide additionai support when mining appr& within closaprorrimity to the site.
135 Figure 37. Application of MineguardfM over bolts and screen, as a shotcrete replacement at Crean Hill Mine, 3800 Ievel garage The actual application was achieved using personnel from INCO Mines Research, with application specialists, Engineered Coatings contractors. This application used INCO's second-hand equipment (Figure 38). which was pmhased h m Shaft Machines, Richmond Hill, Ontario. The pumps and parts were completely overhauled by Mines Research Department prior to underground use. Figure 38. inco's second-hand polyurethane application equipment in this application, the product was grey in colour - it was material that INCO purchased from Shaft Machines. Due to the storage time of the drum sets, the manufacturer recommended that the resin be re-mixed at the Urylon plant prior to the application, to ensure the additives were evenly distributed in the drum. This raised important considerations at INCO regarding shelf-life, storage, and requirements for inc0 procedures in mkdg/applying the products.
136 The total surface m a for coverage was 612 m2, within the main garage (283 m') and in the turn-amund (329 mz). A scissor-lift truck was used by ihe applicators in order to be able to reach the high back, Figure 39. Figure 39. Application of MineguardTM from a scissor-lift truck platform Dunng the application, isocyanate monitoring was conducted (bot' workroom monitoring and personal) by the Occupational Safety, Health & Environment group. Details of the testing are contained in Section 4 of this thesis document. 338 Trial #8: Copper CUBSouth Mine, 2520 Levei, VRM Top Si In 1997, Copper Cliff South Mine initiated an underground triai to test the effectiveness of the Mineguardm liner as a replacement for shotcrete in the bulk mining stopes. Nomally with the Vertical Retreat Mining (VRM) method, the top sills undergo extensive damage due to blow-back frorn the ïïh (in-the-hole) blasts. In some cases, the damage to the top si11 is very severe and requires complete rehabilitation during the rnining phase of a particular stope. Some top sills have become extensively darnaged, with the added problerns of high stress and unraveling of the mkmass. Delays to the production xhedule have an enormous impact on the economics of the operation - shotcrete is an option for preventing costly delays.
137 in the 1990's. South Mine began introducing shotcrete into the operations to pmtect the screen and bolts in the VRM top sills. For the most part, shotcrete has eliminated the need for reconditioning in these sills. However, the shotcmte application has also added some complexity to the shaft and level operatioas, for transportation of many bags of material hm the sudace to the underground stopes. In some areas of the mine, the Ievel haulage is congested making the materials handling pmess very time consuming and labour intensive. The Mineguardm product, with the advantages of low materials handling and high productivity application rate, offers a potential alternative to the shotcrete product. For exarnple, one dnim set of MineguacdTM (sprayed 4 mm in thickness) is equivalent to 33 bags of dry shotcrete (applied 5 cm thick, or 4.2 m' per bag). At South Mine, the 2520 Level top siil was supponed with 5 dnim sets of MineguadIhf materiai, replacing the need to handle and apply 165 bags of dry shotcrete, Figure 40. A conuactor was used for the application. Figure 40. Rail transportation of MineguardTM material to the application site The trial was conducted in an old mining area, during the final stage extraction of the ore zone at that elevation. The top siil was excavateci very early in the mining life such that the condition of the pund at the time of production ciriiling was very pr. The rockrnass had degraded, with loose rock bagging in the screen. The stress redistribution in the area also caused the rockmass to become broken up. Due to the extreme cracking and joint dilation, it was a chaüenge for the crews to effectively knit the rockmass together with the thin coating. The materiai adhered weil and provideci excellent coverage to the bol& and screen, figure 41.
138 Figure 4 1. MineguardTM applied over bolts and screen as a shotcrete replacement The blasting in the stop was not entirely trouble-free- lth drilling problems were encountered with the broken ore, leadhg to deviation in the holes. Upon blasting. some biastholes detonated with high vibration and concussion levels and with extensive blow- back from the holes. The trajectory of the blow-back matenal (mostly crushed rock and slag) impacted on the MineguâCdTM lining in a few locw areas of the back of the top siil. As a resuit of the blow-back, the blasting string would become entangled in the mesh, even with the Mineguard coating, Figure 42. The blasting crew did not like this aspect of the MinegudTM and preferred the smoothness creaied hm shotcrete liners- Figure 42. Blasting string caught in the screen, even with a Mineguardm coating
139 At the completion of mining in the stope, the top siii was re-examined Aside h m two localized areas of damage (due to extensive blow-back). the Mineguard"( provideci excellent secondary support. In 1997 (following the success of the first test application) another large top siii area (7306 stope, 2520 Lievel) was reviewed as a candidate site for another MineguarcP application. The site represented an area of 230 m'. The Mineguard~ could be applied with 17 drurn sets of material, versus a need for 750 bags of dry shotcrete. Again, an experienced contnctor would be used for this application, to perfom the work and to train INCO crews. This project was conducted in partid cotlaboration with Mines Research even though the appl icabili ty of using Mineguard- to replace shotcrete was already assessed during the preceding trial at South Mine. Mines Research aided in the training of new crew members and in assisting with al1 technical and administrative issues. The actual initiative was put-forth by the mine operators as a cost-swings maure. The top si11 area was located in a remote region of the mine, again, where the transportation issues surrounding shotcrete were prohibitive. From a timing viewpoint, the Minepardm process cm be completed in 34% of the time to shotcrete, Figure 43 wobson et. al., SHOTCRETE - ~tarts 1 Delivery mat'l to station Material to work site Spray Empties to station ôh 25h 625h - 2m 125h SHOTCRETE - Finish MINEGUARD - Starts ] a 1 l~aterîal l2 SPMY l3 Empties to station 1 l4 km~ties Delivew mat'l to station / 0.m - - to work site 1 2h 1 'Oh 2h to surface 1 O.7h 1 I Figure 43. Material handling and application cornparison: shotcrete vs. MineguardTM. mobson et. al., 19981
140 Overail, a cost analysis by the Divisional Supervisor at the mine site. indicated the benefit of replacing shotcrete with the polyurethane coating [Darling, As a further effort, a peer review of the support practices in South Mine's VRM sills was perfonned by a Leadership 2001 Team at INCO mobson et. al-, A cost analysis and advantages/disadvantages report was prepared and presented to INCO management in Aprii 1998, Figure 44. The costing includes tangible and intangible items for two secondary support systerns (shotcrete and MUieguardTM)- The foiiowing cost categones elecuicity, and Wear, etc.). level transponation (manpower and equipment) (3) application: labour costs, (4) equipment: capital cost (purchase or lease), maintenance and repair. (3 rnisceilaneous: down tirne waiting for supplies / cage delays etc. The cost table includes the estimate for hl1 versus half of the bolt and screen requîrement for the MineguardTM support. In the case of half the bolting and screening, it is assumed that the MineguardTM is used as sole support in the walls of the SUS., Material handling Application (Labour) Maintenance & Repair 1 SHOTCRETE 1 1 MlNEGUARD! FULL FULL 1 HALF 1 Material 72,488 97, ,070 1 Miscellaneous Screen & bolts TOTAL COSTS (S) COST PER SQ.Fï. 51,840 9, , , Figure 44. Cost cornparison of shotcrete versus Mineguard for VRM top si11 support mobson et. al., ,480 3,641 92, , ,539 [ 4,480 3,641 46, , I Based on the cost analysis, the first recommendation h m the 2001 Team was to use MineguardM in place of secondary shotcrete support. Nthough the MineguardTM cost per square foot is slightly more than the shotcrete, the time for application must be considered as well. Compared to shotcrete, MineguardTM is applied faster, which aiiows the crews to rnove on and do other work, There is a tremendous cost advantage associateci with fast support.
141 An additional recommendation hm the 2001 Team was to use the Mineguard" as an up front replacement for bolts and screen in the walls of VRM silis while using bolts and Mineguardm in the back (see: MineguardTM, Half in Figure 44). This option allows for Iess cost per area of rock, and it assumes that the Mineguardm has the capacity to hold the rock together duruig the VRM blasthg. By cornparison, the shotcrete also performs weu but its stiff and bnttle nature ofien requins that bol& and screen also be installeci to handle rockmass deformaiions during production mining. The mine agreed to proceed with the application in In the VRM siil area, 230 m' of rock surface was sprayed with Mineguardm (over bol& and screen), Figum 45 and 46, with mining scheduled to occur in Observations of the conditions are king recorded. Figure 45. MineguardTM application at C.C. South Mine, 2520 level, VRM top siil Figure 46. Mineguard'IM applied over screen and bolts in the 2520 level, 7306 stope
142 33.9 Trial #!k Copper CüENorth Mine, IWO Levd Copper CLiff North Mine initiateci testing of the Mineguardm liner in a sub-level cave minuig area. on the mine's 1070 Level, Figure 47. This test wodc was undertaken in the fail of Figure 47. Sub-level cave mining at Copper Cliff North Mine: Mineguardm applied as a shotcrete replacement on the back and upper walls This area was sprayed with the Minepardm after the complete excavation of the access heading had been completed and after the bolts and screen had been installed. The Mineguardm was intendeci as a shotcrete replacement for the production cycle. One interesting point worth noting is the ease with which the existing services were sprayed around. if shotcrete had been used, the services would have had to be taken down during the application. In the case of Mineguard-, the ventilation ducting and the aidwater Lines were left in place while the crews worked around them, There was also a comment from operations personnel that there was very little overspray on the ducts and pipes, although dunng a walkthrough inspection of the site, a thin coating of overspray was detected on the booms of the jumbo drill. Where there was an oily residue on the cylinders, the overspray could be easily peeled off. Under regular maintenance of equipment, washing of the equipment would remove the overspray, but ody where there is a film of oil on the equipment- For future use, unnecessary mobile equipment should be removed hm a spray site to Lùnit the tenacious Liner coating; al1 equipment in the spray site should be greased.
143 The application probiem at North Mine was the first instance where the dew point quitemens was mentiod by the mdktum to the mining industry. This application complication has since been uicluded in INCO's o p d g pfocedures. At the recommendation of the application crew, large fins and heaters wese brought into the area in an atternpt to diminate the Dew Point Fada IECL, 1996J. This remedial action served to duce the air humidity çomewhat and to decrease the beaded water amtent on the excavation surlàce. EIowever, &er several shifts of down-time, it was d ded to move ahead with the sprayhg despite some unfavourable rock surfàce conditions. In an atternpt to dry the rock wfke, air blasting was used by an operator whereby a blow-pipe was diredexi at the rock mrfàce, blowing compressed air. The MineguarP application followed closely behind the air blasting technique, while the rock mrke was still relatively dry- This process was taxing on the operatam, especially for over-head work However, for the most part, the application was very qui& and the adhesion appeared to be adequate to good niere were sorne lodized irry howeveq, where the liner linald be physicaily pied fiom the rock. Mining in the sub-lm1 area was initiated shortly PAa the Liner application. One comment f?om the operatioris pasonne1 was the ease with which the up-hole couars cwld be located. The drill holes stand out veq black againsî the white liner. From a support viewpoint, the liner was peeling hm the back in sorne localized places, as a result of the biasting, the poor adhesion, and the abrasion h m the scoops. Mer several blasts, the site was shut-down, Bie to pwr grade. At the presait tirne, the rnining in the 1070 location is still onhold.
144 Initiaily the Engineering Design was canpleted, with a ddpild dcmpnd vasw capdy.. analysis Fpley, 1997, Tannant, 1997; Diedeaie 1997, The cpp.city dctamuvbon and support mechanisms are described in deta& in this thesis doauna*. 'Ihe mchgmd trial was designed with ProCadureg data dection recpiremcnts and asessrnent protocds. At the same tirne. a prdiminary produdivity improvement shdy was uiitiated, with some rudimentary procas simutation studies at Mines W h by Codcal[199q. Thetestdesign~Monestopehead'm~bitthiswulataarpanddtohw>trielsiteswithin the active stoping area at the 153 ûdmdy. Wth a view to long-tenn use, it was felt that the testing should be conducteci in pmgrcssively more highly-stressed growd, to ascertaui the effeciveness ofrtud-alone support in providing sdequate capcity as Ming increased. The Engineering Design œrtainly highlighted the amcern of achieving adequate stand-alone support fiom a Liner in sîress-wed grwnd. In early 1998, the field trials were started, to test the effediveness of using a stand-aione spray-on liner for support in a nanow vein mining application [Espley et al., 19971, vmmt et. al., The following data is takem h m a report to INCO fiom the Geomechanics Researh Centre [Tmanî, Geologically, the 153 Orebody consi& of two main ore stringers that are subparallel, very thin in their tniewidth di men si^^ and with extrernely high grades of nickel, wpper and precious metais. The ore seingas are physically aratic, often with one strùiger merging with the aha and o h with many off-shoots and pub-paralle1 stringers Nnning with the main ore lenses. nie zone is appoximate1y 1000-rn on stdcc, with a variable dip (ranging hm very stq, ai: 80 to 8S0, to veq Iow, in the range of 450). approximately 675 m. The ore mne's dip lengh is
145 (2) to support the dabs that are m e d in thc back and dis, and The rationale tor selading Mincguard"' for the testing is pvided in Chapter 2 of this thesis. In 'iummary, the studord support systcm of bolts and saeen is a labour and tirne-intensive process. The MqpanP liner was viewed as a means of increasing productivity in this mining enwonment Fiidd TrUl ni- Cut in The first trial involved t h application of MineguarP as primary support for the stop being drivai dong the sbike of the steeply dipping 0.2 to 0.5 m wide vein of sulphide ore. The stop was excavaîed as part of a narrow vein cut-and-fil1 mining method, esserrtially with the creation of long niirrow drifts. The first cut had previusiy been driven by the mine - this test site constjaited îhe second ait in the narrow vein strings, dvancing toward the west &utment of the wne. This vein was located in the hangingwall, with no sub-parallel vein nuuiing on the fodwall side. It should be mted that many stop (or chias) are planned and laid-out for each mining horizon, since the ore body is extensive in strike. This trial site was the secund-cut stop for a botîom-up mining ssqumce - i-e- even though a mat stop was the prrfemd dioice fw tes&i.ng Aggrcssive mine pmduaion prevented testing in cut #1. Despite this, the pmpovd triai locaiion provideci aomc isolation &om the rrmpinder of the O- and mmequently, interfaence bctwaai the testing and the day-tday opezations would be minimized wiîh the seleded site.
146 Figure48 showmthetoabiaiofthctcscdriacm the42u>lmf ofthe mine (~ocl29srn). The~~~~)~vrtedwrsUnmsdiotely~thekttwrllofthetest~. Thetest section of the drift canpwed eight rwnds (iudindual blasts) with spans that mged betwem 1.5 and 3.2 m and hcights that ranged between 2.1 to 2.7 m. The nrst six rounds were supported with MïncguBrdrY without any addiional support and the finai two rouncis were supported with bits and screen Triol 11 Test Drift \ Figure 48. Plan of McCreedy East Mine, 153 Orrbody, 4250 level: ldon of two test des for stand-abne Min- tcsting
147 The stop was p~pared for the Mineguardn" application akr each blast by rnucking out the broken rock, rahg any loose rock, anci washing the back and waiis. The adhesion of polyu~thane to rock cm be adversely affecteci by wet rock. Therefor~. each cleaned and washed round was allowed to dry under good ventilation conditions before the Mineguard was sprayed ont0 the rock Four point-anchored safety rockbolts were installed in the back of each test section aher the MineguardTM was sprayed. The bolts were installed on an approximate 1.2 m by 1.2 m pattern. These bol& were not preloaded and were used only as a back-up support system in case the MineguardTM liner fiailed. In fact, each bolt end was Gtted with a squeeze block, which was a 10 cm thick wedge of strong styrofoam, and a protective plate. Figure 49. I - 7 Angle Plate (for protection h m blast) (snug Location of Blast Resin Point-Anchor BOI~, 2.1-m Bolt Pl= to squeeze block) Figure 49. Squeeze-block configuration (after Tannant, 1998) Figure 50 shows the appearance of the test drift after the application of MineguardTM within the first three rounds. The Mineguardm was sprayed on the exposed back and wails after each round was blasted, mucked, and washed. The face of the stope drift was not sprayed. A thickness of 4 mm was specified for the back white only 2 mm of Mineguard was required for the s tope w alls. Generall y, the amal Minepard~ thickness exceeded these speci fications. As with previous experience at INCO, the white colouring of the Mineguardm enhanced the visibility in the underground heading. The miners working in the are& while at first suspicious of the product, came to appreciate the support and reflective qualities of the liner.
148 After each blast, the p~eviously coated test sections sustained minor darnage hm fly-rock and the originally white surface gradually became coaîed with dust and stained by the blast gases. This effm can be seen in Figure 50 where the rwnd funhest h m the face is slightly darker in apeearance* Figure 50. MineguardTM applied to the first three test rounds of trial # 1 The performance of the MineguardN and the condition of the stope were examined after each blast. Two boreholes were drilled into the back of each round- For each round, a single-point linear potentiometer (GMM) was installed in one hole to monitor downward rock movements while the other hole was used for visual observations using a borehole camera after the blasting was cornpleted. Figure 5 1 shows a plan view of the test drift, the position of each round, the ore vein, and the location of the instrumentaiion. This figure also shows sections taken through each round. The first six rounds were supported with MïneguardR*[ and the final two rounds were su pported with bolts-and-screen. Detailed stmctural rnapping was performed afier each round was blasted and before the Mineguardm was sprayed over the exposed rock, Figure 52. Three joint sets were found from the mapping conducted in the test stope. Even though many joints and shears were mapped, only a few joints combined to create wedges in the back and walls of the test stope. The largest discrete wedge that was identitied only weighed 1.6 tonnes. The design capacity of both the MineguardTM liner and the safety bolts was higher than the gravitational load (demand) h m aü identified wedges.
149 Round 6 Round 7 Round 6 Round 5 ulphide, vains Secf ions WCCÇCS Round 4 Round 3 - :ci:!s Round 2 - shccrs Round I 01 ' 42 rn Figure 5 1. Plan and sections of trial #1 stope. Location of ore, GMMs and safety bolts. Figure 52. Structural mapping, triai #i. Location of discrete wedges. A problem occurred at the end of Round #6 where loose fnctured rock caused the MineguardTM liner to sag between two safety bits; thïs material was easily knocked down by a LHD scoop bucket. A key factor contributing to the problem was the fact that the liner was not continuous in this region of the stope. In fact, the loose rock was only supported on three sides by the liner. This allowed roof displacements (sagging) to propagate from the edge of the blastdmaged Liner in a cantiievering effect. One positive aspect of this incident is that the MineguardTM liner gave ample visual warning that excessive displacements had ouiurred. For the trial, seven single-point iinear potentiometers (GMMs) were installed in the test siope to measure non-elastic rock movements. The maximum vertical movement was about 10 mm, Figure 53.
150 MUieguardci" likely iimited the downward rock displacement and dihion, and preventsd ultinate collppse ofthe rock ErCnlonamr 8 reundm were bhmud no extensometms wire In8C.U.d untll dtor R3 x x y x x R3 R4 RS RI R7 Rb? I I I I I l Figure 53. Convergence (vertical, back di splacement) measurements obtained fiom the single-point linear potentiometers, GMMs Borehole camera investigations were conducted in boreholes dnlled into the back of the test stop. The maximum depth of observable hcûukg was 0.4 m, alukwgh typicaily the h&g only extendeci to a depth about 0.2 to 0.3 m The reduced stop span and a gde arch in the back aidcd in minirnizing the depth of fktming in the stop back Five in smi adhesion tests were pedormed on the Mineguarbnr in the test driff [Tannant et. al- 1998; Sutherland, The test pocedure requins that paforaid discs or dofies are aüached to the walls of the stop using MineguarcP? A quick application of Mineguard is made, and the disc is pmseû onto the liner immediateiy, to allow the disc to become partially imbedded in u# liner. Another coatuig of MineguarcP is applied over the disc assembly.
151 Once the liner is completely cwed, a co~g drill bit is used to score the MineguardTM anwnd the disc. to completely detach the testing disc h m the surrounding her. A puii-test unit is attacheci to the disc and it is then systematically loadtxl, to pull the adhered MineguarcTM h m the wall. Examples of: (1) the perforateci disc (or doiiy), (2) the over-coring drilluig, (3) an installed and CO& disc, and (4) the pulied disc are show in the foliowing Figures Figure 54. Pull-test dolly Figure 55. Overcoring procedure Figure 56. Instailed disk Figure 57, Pulled disk Adhesion strength testing of Mineguardm The adhesion measured between the rock and MineguardTM Liner varied widely hm essentially no adhesion to 0.8 MPa The effect of moisture or dust on the rock swface is an important issue. The MineguardTM adhesion was poor where the drying time was not adequate. Furthermore* Fracnired sulphides in the ore veins also duce the effective adhesion to zero. This is because the ore itself is much weaker in tension than the MineguardTM. An exarnple of poor adhesion in the test drift is shown in Figure 58.
152 Figure 58. An example of poor adhesion with the MineguardTM liner on adhesion tests and a back-anaiysis of the small scoopassisted fall of ground at Round 46, the actuai liner capacity in a bagging mode of behaviour appears to be roughiy 3 to 4 kn/mm This capacity caiculation assumes that the loose rock is suspended by the bagged liner and is held by a combination of the tende and adhesive forces in the liner around the perirneter of the Ioose rock, Field Trial #2- Cut #3 The second trîal involveci application of Mineguarda to hvo rounds in a 3.0 to 4.3 m span stop that was driven dong a swann of sub-parailel, steeply dipping veins, Figure 40. This test stop had a wider span and higher rnining-induced stresses in the back compared to the fint test stope. The stope was excavated as part of a cut-and-fîii mining method for the nmw veins and it was the third cut in the bottom-up mining sequence. Cornpareci to trial 61, this stope had greater stress-induced fracturing in the back of the heading. Figure 59. The test stope was located in the centre of the nanow-vein complex. as shown in the previous section.
153 Figure 59. Stress slabbing in the back and walls of the narrow vein stopes. 153 OB vains figure 60. Two test rounds in cut #3, trial #2 Application of the Mineguardm followed similar procedures as were adopted for the fmt test stope. The Mineguadm appiication and its subsequent performance were unevendul for the fmt test round. However, whiie washuig and scaling the roof after blasting the second.test round it was evident that stress-induced fracturing was occumng hm the sound of "rock noises" in the back and shoulders of the stope. The noise (fracturing) appeared to originate near both shoulders of the stope. This noise seemed to be caused by the scaling and recent roof was hing ac tivi ties.
154 The swnd of rock fracturing stopped shortly after the scaling was completed- However a few hours later the noise reappeared and intensifkd, leadhg to a fall of ground near the face of the stope. The ground fa11 consistecl of a stress-fractured slabs of rock that feu from in the back of the unsupporteci round; Mineguardm was about to be applied- In a pst-analysis. the back appeareà to sag, under gravity Ioading, immediately before the siabs of rock fell. The slabs originated near the boundary of the MïneguardTM coated area from round #l and, as a result, some of the previously applied MineguardTM was peeled back by the fall of ground. The largest slab that feii had an approximate size of 2 m x 1.5 m by 0.2 to 0.25 m thick. Al1 the rock that feu was slabby and stress-hctured in nature. En totd, roughly 2 tonnes of rock feii h m the back Figure 61 shows the resulting fd of ground as weil as the MineguardTM that was peeled back from the back of round #l. It was obvious that the stress fnçtured slabs extended from round #2 to round #l because, coincident with the fall of ground, the back at round #I suddenly moved downward about 50 mm (as detected hm the installed GMM). Furthemore, the sdety rockbolts that were installeci in round #1 Iikely prevented the existing slabs from falling down in that area as weli. Figure 61. FaU of ground in round #2, trial #2: induced by stress fracturing and incornplete MineguardTM coverage
155 Rrnmd #2 wrs excavrted with a vay flat badr and r wkk span (3.6 to 4.3 m) than the iùs& test stope. Given the depth (stress level) and geometry of the test stope, stmss-duced f%tures grow sub-parailel to the bacû, even if they cannot be seen A flat back and relatively - - largespanctcateconddknijwhaethe~ofrockcanbequitethidcudclwaawideut.. The progressive nature of the &on of slmsshdcd fractures rneans that the stability of the back changees ova thetime As the fktms grow, horizontal slabs are & that can intersect the subvertical ore veins, and hence break and sag/deflect downward, In gaunl, sinwinaiced fipchins originate at the CO- of the drift and propagate aaoss the back At high stress levels, an archeci back can be used to Iimit the depui of stress hctured ground in the back. This will Iirnit the demand that is exerted on the support systern Once is initiated, the arched-back wiil yield a more stable excavation than a flat-back heading [Uartin et al., The aaual engineering design (for the testing at the 153 Orebody) recommended arching of the stope backs to reduce the depth of failure lespley a. al., 19971, aîthough this suggestion was not practiced routinely derground- In high-stress regirnes, Mineguard"' shwld be used with the addition of rockboltits. There is a potentid, however, to install the bolts on a wider spacing with the lina (Le. as compareci to the bott spacing airrattly used with screen). nie back must be SOUtded anci scaied immediately before application of the and bol& must be instrrlled as soon as possible after spmying. Fwhmmm, the blast design should attempt to aeate an arch to ttie back and the blast should not excessively damage the rock Based on the 6ndii hm the trials, the span limitation may be rehed with haire impmvements in the understanding of the supporthg action of spray-on membranes.
156 Like screen, does mt pdom well wkn subjd to repea&d scoop abnsion. Thescoopc;sncltchonsdgeofthelinerdte;iroffh. niebaiefitsofspraying MkguanP from the bock to the floor in an adive headii w h quipment ckance is minimal should be reviewed in light of the poteritid for darnage. Mineguardrrr appean to sustain only minor damage fiom the fise blasts. The fiy-rock causes srnafi nicks, arts and abrasions and may remove small patches of the v. The damage is most pronounœû where the supported surface protnides slightly into the excavation or on suraices that fiice the biast. As arpected, the worst damage ocairs immediately adjacent to the t8ce. At these locations, the blasts can cause the Mineguardnr to peel back about 0.3 to 0.5 m h m the hce The overlap in the Mineguard Kner between rounds is a soufce of iiner wea)oiess and operational dfiailties. A method is needed to deal with the ragged debonded edge that forms adjacent to the newly blasted fpce. Experience underground Uidicated that the liner edge is diffiaih to trim and respray, which results in a pmr interfàce and a weak point in the liner support system. A recommendation worth testing is a tapering of the her thickness towards the t'ace. Also, the Mineguarariw edge can be ended 1 m fkom the flux to minimize the &ed As a result of the fidl of grwnd in round #2, îkther emgineering design was undertaken to determine the capacity of liner support for a partially c~afed back Specifically, if the back is not fùlly mvd with MineguardTM, d l a wedge or loading of stress-slabbed rock be sufficiently supporteci? This question is paramount to the safi of the operator who is required to enter the Ming in order to effectively apply the MineguardTM to the entire ôack
157 Atthe tirne ofthetid, thaewasm robotic means ofapplyingmkgunp -this hes sincc led to firrther resarrdi into apipmcnt design, as discussed in more detail in this thesis doaunent. In summacy, a d e and efficient means of applying a sprriy-on support lina rsquirrsthedenlopmcrit~fappcqrb~pment. Aiobcticsprayarmisnocdedtolpply the MkgmnP aidi that the opaator is never rquired to adah neaily blasted round. The two documented Mls of ground d where the MUieguard'w liner did mt exist up to the fàce of the Moi In thest situations, the saessdamaged rock in the back was able to rnove downward nerrr the fàœ forming a cantilevered slab because it was unrestrained, Ultimately the slabs of rock tome thriough the MineguardTW at sorne distance f?om the fàce. In conclusion, it has becorne evident thaî &&ive Min- support is created by a COnfjl#lo~(s membrene that is M y &red to the rock Adequate rock h g, cleaning, washing, and drying are essential for g d adhtsion Smoorh liner ovahp between munds and adequate liner thickness (to bridge al1 rock -oints) are essential fik d g continuous membrane. The use of a robotic spray am removes the risk ofground Wls while building up a continuous liner owr the compieie d c e srea ofthe back and upper d s. a M~IKsR~s~&,~~SOW~B~~ The Research Mine at INCO Limited is referred to as the 175 ûre Body. This mine is located to the mrth of Copper CliflFNorth Mine, and is the a. downdip extension of the North Extension Pi that was mined during the 1960's and 1970's. A nunp was driven 6iom a swfk portal to the 530 Level (160 m depth). W~th Iow nickel prices in the 1970's, the mining of the low-grade material under the pit was halteci and the mine was closed.
158 More recuüiy, Mines Research bps mpened the mine fbr tesîïng of Minhg Automation Equipment, as part of an Automation Program at INCO et ai, New technologies and mahods will be tcsted in this mine, with an aim to implernent the suaadid projezts into the INCO Olaario Division mining opa9tions. (1) Waii Support, to Repiace Bohs and Screen: In place of conventional ceconditioning with bolts-atd-screen, a sedion of the mine was sprayed with M i n e for wail support The application todc place in an dd rwm and pillar mining zone, with deteriorad grwnd conditions and completely corroded initial support (boits-and-sc~een)~ The liner was also applied over some new!y inded bohs-and-saeen, in a garage bay. The excellent refidve quality of the liner is always remarked upon by visitors to the mine. The liner application was supplemented with in situ adhesion testing [Suîherland, 1997, Tannant, Adhesive strengths ranged hm 0.53 to 1.17 MPa The low values were obtd fa MineguarP applications on conmte blodcr (on a ventilation wali). Other adhesion tests for altemate product testing produced some extremely low results,butthesewereduetop6oc~~ltfaccprepbfotiolswhcrcbydustddirtwpsno~ adequatdy removed hm the rodc prior to the üner application. lhese adhesive strength tcat( anpiuasii the aiticai impocunce ofcleaning the mck Surnce for proper adherence of the polyurethane liner.
159 Acomp~wahthtaiguul~~rndtheIppüatioawu~ WithresuttsthattheapplicatiorwofthttwolinapoduasueKktiticsL Adhesiori pull-disks wae poorfy located in the spray site arh that bw adhesions were oboincd. These low values were due to Mure of the rocbnass, rather than the liner to rock interfàce. Additional laboratcny testing has cunhned Rockguard's quivalent adhesion to the MineguarP product, with values ranging betweai 0.25 to 0.94 MPa Damant, Physically, the Onginal RockguarP pdua appears more shiny and glass-like, 8s compared to MkguamP. Also, it is mon biale than MineguarP with lower elongation pr~perties~ The stifl6iess of the new fodation is graita than that of MineguatdrY, although the load-canyuig capacity is quivolent (Tannant, A new RockguarP formulation is available ftom Futurs, with similar materiai properties to MineguardrY. (3) Slough C o d on Development Faces: R- (nnt gawration) was appiied ont0 tk rock îàces of two dvancing dmloprnent hcidigs. This research was airned at diminating the slough that fpus fiom the fw during drilling of the development d. Initially, the drillhg indicated excellent cdlu codins, with no cnrmbling and det ehdon, Figure 62. ~wcver, aiter s d hoks were ddled into the faa, the liner was f d to be walcing ahst too wd.
160 In fact, the liner held the rock face together during the drilling process, yet the vibration hm the drilling caused the rock to pull-away and spaii behind the liner. This failed rock matenai was not able to fail to the floor due to the constrauit of the liner. Consequently, when the Ioading crew entered the heading to lod the explosives, inany of the collar holes were plugged or blocked with rock fragments behind the liner. The premise of the Liner testing on the development face was to hold the rock together to assist the explosives ioading crew in preparation for blasting. Furthemore, slough control at the face is critical for automation processes to prevent the need for humanintervention for cieaning the rock pieces in front of the lifters (as with the current pnctice). Figure 62. Rockgud coating on a development drill face: testing for slough~spakontrol and collar integrity (4) Remote-Control Application: Testing of remotecontrolled application equipment was complet& in April 1998 in the main nmp of the 175 Orebody- A spray arm with remote contmls were fitted ont0 a Kubota-520 (underground tractor), in order to test the application process for Mineguardm, Figures
161 Figure 63. Rernote-control application of MineguardTM at the 175 OB Figure 64. Spray gun mounted on the arm Figure 65. Arm and gun remote controls The actual application was very easy once the operator became acquainted with the remote control switches and joy sticks. One feanire of the ami, thaî of an oscillating head, aiiowed for the cracks and joints to be infiltratai with the liner. The oscillation capability was deemed necessary by the application personnel, especiaily when cohnted with applying a liner on a very rough rock contour. Overail, there was no difference in quality of the applied liner, comparing the rernote application to a manual process. The equipment and application process could be fwther automated. For exarnple, controis and programming could be used to apply specified Liner thicknesses. Once input, the ann could then travel at a specified speed andor with more passes to establish the required thickness. As weii, a distance rneasuring device couid be used to profle the heading and to meûsure the distance of the spray gun to the rock surfiux This wouid allow the spray-gun to foliow the exact contour of the excavation, for remote-controlled or automated application of the liner.
162 (1) Stobie Mine, Lunch Room Application: MUwgundn wu appiied to the 4 s and back of a - u excavation that samdasarctiigeslioaudlunchra>m ~linawrr~tourltheexmvation a d prevc~ the influx of W. A nuigustyp mataid acarnulateà in thc rwm, which was un;ippaling to the workao. nie Cndvely corted and contahed the excavation to enhance the hygiene in the nxwn; howtver, this was a short-lived sohitior~ Unfortwiately, the source of the fungus was hm within the humid mm itself Dcspite the inability to solve the nuigus infiiy the cuaîing was hvourable with the added bght reflectivity in the excavation, (2) 175 OB, Rcsearch hdïne, Ventilation Barrides: A unique application of MuieguardTM was tested at îhe 175 OB, in the vicinity of the 152 mm-and-piuar workings. For a contmlied ventilation system, the area d e d to be ded ofs to prmnt mtilation losses to an iniccasible adjacent mining ares- In place of labour-intensive and time-consuming construction of timber ventilation barricades, MineguarP was used to coat a suspaded sheet of geotactile material, Figure 66. Wmdai slats were used dong the excavation pairneter, ad attached to dsting rockûofts, to hold the F M in place without ripping h The M e was nntha sûmgthawd with welded-wire rnesh, suspended fiom the behind the Fabrai&. (in two sets of screm amid k ustd to sandwich the F M. ) The MineguarP was then used as glue, to stick the Fabre& to the rock and d the outer pairneter of the excavation. Then the entk Fabre& surf& ans spraycd with a thin laye of MineguPrdTY. ui esence, the impavious nature of the M h p m P üna material effedively prevents ventilation losses thnwgh the From a time study, two large ventiiation barricades were indd within 3 hours (each bsmcade king 10 m by 10 m, 1ppmximaîe1y).
163 Figure 66. Construction of a bhcade (stopping) using Fabrena and welded-wire mesh: MineguardTM coating on the barricade prevents air losses (3) 175 OB, Research Mine, Sump Station: The sump station at the 175 OB was sprayed with a polywethane coating in the fail of At that time of year, the sump station was extremely wet, with water dnpping and pooling onto the floor. The rock surface was very dirty, with thick accumulations of dirt and oils hm the previous mining and rehabilitation operations in the mine. An attempt was made to dean the rock surface as much as possible and to aiiow for adequate drying tirne. However, with constant ground water inflow into the area, the MineguardTM was sprayed ont0 wet rock. Approxirnately 75% of the area indicates good adhesion, with appmximateiy 25% of the area with smd-sale peeling and poor adhesion. These adhesion problems ate mainly concentrateci dong the Lower walls where there is iittle concem for lack of suppor~ Since the application, a concrete floor has been poured in the area, and the sump is used for process water storage. The enhanced light in the heading, due to the reflective qualities of MineguardfM's creamlwhite colou~g, is excellent. As a muit of this applicaîïon, the importance of shelf-life and temperature of storage for the polyurethane matenals was raiseci. In this are;i, the Liquid materials used for spraying were quite old and could have been exposed to cool temperatwes during the fall.
164 According to the application experts [Corbett, pers. commun , the water scavenger within the min rnix WU ofien become us&-up in dealing with air humidity dunng storage. This is especiaily ûue when the d m have ben opened and if t h is no nitmgen blanket as a humidity barrier. In these scenarios, the sprayed product will not have sufficient water scavenger lefi in the mixture to handle any surface moisture. As a result, the product wiil tend to foam, it will be weaker and it wili have very poor adhesive strength. (4) Lower Coleman Mine, Conveyor Belt A conveyor belt at Lower Coleman Mine was coated with a paintable polyurethane material, to increase the life of the belt. Apparently the application was very successful, but there has been no recent communication with the mine site personnel to attest to the performance of the liner. (5) Clarabelle Mil, Tanks: The tanks within N O'S Clarabelie Mill were beginning to show signs of Wear and corrosion. To protect the tanks and ensure many more years of use, a polyurea material was applied ont0 the steel surface inside each tank, Figure 67. The polyurea (almost identicai to a polyurethane in physical properties) was applied by îtw Foarnseal, a contrac~g Company hm Michigan, USA- Figure 67. Application of poiyurea material in the tanks at INCO's Clarabelle Mill
165 This application was completed with relativety highend application equipment, Figure 68, that was programmed to alarm as won as pumping volumes. etc- were altered beyond a set range of acçeptab'ity. This quality control aspect was most impressive to INCO. Figure 68. Application equipment for polyurea materials Furthemore, the application crew for the project were able to complete the application within two shifts. There was no requirement for dismantling or cleaning of the hoses, spray-gun and materials during the off-shift. The crew retumed to the site and promptly resumed spraying. The polyurea, apparently, is more forgiving for long delays between applications as comparai to polyurethanes. Cornparatively, the equipment used to apply the Mineguard~ product must be cleaned if the materials have more than a one-hour downtime (or less). On the bais of the early trials and subsequent applications, Mineguardm support has been assessed to exhibit remarkable production potential (due to high rates of application, low materials handling requirernents and the like) and an ability to provide near-instant support res is tance fol10 wing application. A MineguardTM implementation program has been developed for the K O Ontario Division mines. This program has inctuded the purchase of spray equipment, training of crews, and documentation of al1 procedures and protocols for mate rials handling, rnedical surveillance, environmental control and assessments-
166 Field application resarch of thin membranes (prticulariy polyurethone d pdyurea matmals) continues to be promotai by IWO. It is paaived that these poducts exhib'i trernendous support pdaitiir in dwtions where short tmn, standdone support is need+d to in- pmhtivityvity The application of thin spray-on coatings ova top of saan dm holds greot rpperl. The more raxnt trials have proven tb mpport capability ami eff'veness of using thin linas ta replace secondaq shotcrete support in blasthole siil headings (althwgh use in VRM top sills is nd yet proven) and as a replacement fiw bohs and screen in the walls of siil headings. If undaground triols dso prove positive, it is dso fores#n that rapid-settin% membranes cwid be used as an effective saeen replacement in the backs of production headings with an cxpuded pattern of bolts. As weü, these liner systems may prove to be appropriate for use as a complete replacement of screen (and with delayed bolting) in conventional ddt develqment opaations.
167 HEALTEE, SAFETY & ENVIRONMENTAL ISSUES Wdhthe~of~sp.yonünartothcmininginbby, the- andenvironmerit.loon#nshvebeenaddrcsscdto~the~. Ovenll,the poi~produdb8stlrsemrincharrictensticsthtoouldpotaiti.llyinfl~~1~~tbchczltb of wo- s&ty 1) the liquiô component is an isocypnite liqui4 which mphs spacific tranqmrtation, huidliig d storage requùements, 2) the poduct deases oirbonit izrocyanete particles during the application, and 3) ovaspray sdid mstai.l, created duhg application, muid pose an inhalation conani and a possi'ble explosive dust concem_ The aspect of material flammability is rddresssd within Section 5 of this thosis. is a -part poiyurethane coating system cotnprising a diisocyanate, namely, 4.4. Diphenylmethne düwcyamte (Part A) and a polyol resin part B). Component A is a clear straw colourrd liquid with vay low odeur Md a ~ p pressure w of kss than mm of mercury at m m tanpaature. Cornpanent B is an opaque resin. The min is a mixture of hydroxyl and amine pdyols as well as various additives such as cataiysts, pigments and, cross-linkers. The t\iro Liquids are mùted and appiied at high velocities mto a surtace, fonning a 1000/o solids polyurerhane d g. Isocyanates are man-made organic chemicais. Some isocyanafe~ are used as chernical intdiates. Ovaali, the polyurethane indusby is extensive whereby po1yurehne materials are widely used in the maraifacturing industry, fot such COM~O~ items as fhiture cushions, automobile dashboards, boat flotation, electrical scaling compound, applîance insulatioq clothing insulation, paints, proiective cuatings and bathtub moldings. PoIyurethaiies are also useâ for many types of cuatings in constnidion pmjects to iine wata towers, sewage tmîment tanks, digeration units and the inner waüs of trucks and ships holding areas. In fact, thac are no firmes or off-gases proâuced du~g application ofpolyurrtharig, since thae are m solvents witlün the mu1 This has allowed fbr spraying wïthin food plants without intmpting the food manumg process.
168 Part A, bebg an isocy.iyic pmvinceq states and c h. is a designaîed substance in Ontario and in some &ber Part B is a polyol resin, 1WA soiids moterial, and W not a Parts A and B are hcateû ud prrssurued separately, and the pmducts corne hto amtact with each other outsi& of the spray gun The ractiai is exoawnnic, initpting npid polymerization (or &g) of the two chemicals. Coatings are normally sproyed at a hose temperaaue of 140"F, giving rise to an ultimate aotherm temperaaire of 260 F. MineguardrY beoornes hard to the touch within 10 îo 30 seconds of king applied. Chemically, isocy8n~fes have the generalized formula. R WCO) *. One product in the isocyanate chernical group is methylenediphenyl diisocyanate (MDI). DUsocyanates are mainly used for the aeatiori of polyurethanes. By their nature, isocyanates are readive. At temperanifes bebw 50 OC, MD1 WU react very slowiy wïîh water. This d o n progressively kter as the temperature of MD1 is increased. becornes When parts A and B are mixed and reacted togerher, the cureci polyurethane coating does not present any known hazard - it is an inert material. Fwhmme, once the chernicals are mixed, thae is m longer an i~ocy~nste componnt in the solid dng. The actual chernical reaction is shown as follows, Equation 1 : POLYOL + DIISOCYANATE - POLYURETHANE (Equation 1) OH-R-OH + OCN-R'-NCO - C-N-R'-N-C-0-R-O WI II OH HO
169 DIISOCYANATE + WATER = DIAMINE + CARBON-DIOXIDE (Equation 2) In addition to the d o n of isocyanate with wata, a second d o n occurs (Eqution 3) betweeri the amine and isocyanate, to form a polyurea component: D m + DIISOCYANTE = DIISOCYANTOPOLYUREA (Equation 3) H2N-R'-NH2 + OCN-R' -NCO = O-C-N-K-N-C-M-NCN-R'-NCO IYI III Note: R and R' represent arornatic radicals that are constant parts of the formulations 1 rrpnsenis a single bond found between nitrogai and hydrogen represents a double bond that is fond between arbon and oxygen The properties of the polyurea (Equation 3) corting are différent fiom polyurethane. nienfore, it is very important to contd the water in the application equipmenî anci in the application environmait. The wata d d be in the iiquid fom (Le. faud within the hoses, in the spray gun or on the substrate surfàce) a in vapour fom (Le. as humidity in the application heading). Air humidity quires thaî the pdua be std in Sealed dm- nitrogen blanket to pcmii a dwmid d o n each with a dry between water vapour and isocy81i8fessocy81i8fes
170 Figure 69. Non-cellular versus foarned polyurethane/pcdyurea coatings With respect to heaith and safety of indusuial workers, there are guidelines and legal requirements for reference when establishing interna1 procedures and policies. The exposure guidelines and requirements for specific designated substances are contained in a number of source documents to the mining iodusûy. The following definitions are provided, for reference to the guidehes for isocyanates: - Time Threshold Limit (TLVs) are defined by the American Conference of Governmental Indusuial Hygienists (ACGIH). TLVs refer to airborne concentrations of substances and represent conditions under which it is believed that nearly al1 workers rnay be repeatedly exposed without adverse health effects. Weighted Average (TWA) values iue used for occasional excursions above the TLV, provided this is compensated with the occasional excursion below the TW. This factor applies to an 8-hour work penod, whereby the recommended average value is provided to the industq/manufacturing Company.
171 (1) Wiratory: At m m tanpaaaire, MDI has a low vapour pressure and it is unlikely that a wwka d l be exposed to haaudous concentraiions of MD1 vapourvapour contrai mcaz~uw must be in place for the toüowing situations: However, effective (1) when thc isocyanate produa is heatai in a confined environment fot application 0.e. > 40 OC), and (2) whai spraying isocyanates whereby an a erd or fine dust particles ofmd1 are created. Inhaling MD1 concentrations (weii above the TLV) can cause adverse health eff- such as beadache, nausea, and tiwaî and lung irritation The effi can lead to bmnchitis and is some cases, pulmonary edema Full recovery is possible with appropiate treaément. More cummoniy, workers develop an allergy to isocyanates. This may be manifd as branchial asthma or hyper-feactive response. The allergy may develop a h a day, a wdq or evai. years of exposure. In addition, it may develop due to an ova- exposurc cpisode. Once sensitizaîion ocaus, exp0s.n to isocyanates (even et low threshold kvels) rnay cause sensitiiion symptoms to reap, such as: coughing, shortness of brmth, tightness of the chest, and wheezing. This response may ocair immed'iy or der 12 hours or more since the exposure.
172 Fust aid pmcedurrs for ioocyuuite contact with the eyes are as outlined: 1. Immediately flush eyes with plenty of water for at least 15 minutes. 2. Seek medical attention if redness, itching or a bunring sensation is expezinced. (3) Sb: If isocyamtes wme into contact with the workds skin, a tempocacy discoloration may occuroccuf AAa rrpeaied or prdonged expowe, skin smsitization may OCCUC. First aid procaiurrs for contact of isocyvute~ with &in are as foliows: 1. Remove contamhkd dothing 2. Wash MD1 off the skin with plenty ofwater and soap. 3. Se& medicai attention ifredness, itching or a burning sensation is experienced. (4) Digestive System: If ingested, isocyanates may produce some irritation of the digestive systcm. chemid is reltivdy benign; however, medid attention shaild be The First aid pmdmes for accidental ingestion of isocyrrutcs are as follows: 1. Driniconeortwoghssesofwater. 2. Consuit medical personnel ifgasbointestinal symptoms develop.
173 Since the isocyanaîe material is classi ied as a designateci substance (hazardous material), an understanding of the product and its characteristics are required ptior to using the product in the mining environment or withh a surface plant. Material Safety Data S hem are requiriid, with correspondkg MSDS labels on the product containers, Figure 70. Figure 70. Drum labels, as supplied under WHMIS guidelines The MSDS are supplied with both iiquids (Le. the isocyanates and the polyol resin) by the manufacturer and shodd be reviewed prior to purchase 1 transportation / Iiandling / appiication, Prut A of the formulation of Mineguard'fM consists of a clear straw-coloured Iiquid witli very low odour and low volatility at room tempetature. h façt, water is approximately 100 times more volatile than MD1 (Le. water evaporates 100 times faster than MDI). Even tliougli NIDI is a controlled substance, as of February 1995, it is no longer regulated by the ~Liinistr-y of Transportation as a Dangerous Good [Geaman, 1995; IATA, As mentioned in the early section, during the application of MineguardThf, the two ctiemical components are mixed to react within seconds to form a completely reacted polyuretlime solid membrane.
174 When initially spriyed in.tanled fonn, a d l perce- of the isocyanaîc liquid becomes airbome;thacrirbomcprirticle~ofi~~a~ruktounprotsdcdworlar, b g h inhilrtion SpsCincaiIy, the caiaiyzing agent is an MD1 (methylene biphcnyl isocyamte). Though mt a aranogeq thb ch-cai may cause respstory hitation, when inhaled in high concentrptions, and possi'ble senstijatinn ond g e d n response in humuis. of estfimatic In closed mine emruormiay *ai hahb and dety prorplltinns are thdofe recammendd to peveat ury spray source and inadvc~tnt domrstrerun expomre to underground pasonnl. In bxy, howevct, if the two components are rnixed d y at the gun the chemicai r&n should be near instantanous (Le. les than 10 seconds) and the aîomized maicriai is convated into polyurethane and becomes a nuisance dust. The cecommendecl TWA for nuisance dus (inhalable) is 10 mg/m3 for an û-hour period [ACGM; 1 q. The rate of dmlopment of scnsitizatïon and the degree of the sensithation ~cverity toward içocyanates varies for each individual. Sensithtion can also ocau with repeated contact between an individuai's skin and the iiquid isocyanate p dud Protective gioves (over htex) are recommended for al1 personnel involved with the handling / transport / appiication of the Mineguard'w iiquids. The Design- Substance Regulation û42 rrspeqing Isocyuiltes rpplies to the spraying- Wtthin this Regulation, personnel in the application area are required to Wear a respirotor sudi as a "positive pressure suppiied air respirator with faocpi- or hood or see contained apparatus with tiiu f-piece". The breathing apparatus should have its own independent air supply or be conneded to a compressed air supply that is fiee of water, dirt, oil and orha cotitaminants. In the underground environment, the mmpresd air lines are nd approvcd for use as an air source; this is because there is m guarantee of the oxygen content within the comprcssbd air hm. Air-pwisling respiratocs (carüidge or canister type) are not approved by MOSH fiw proceaion against overexposuce to isocyanates PCI Pdyur;ethanes,
175 The MSA-type of face-mask with positive pressure air supply is shown in Figure 7 1, while the seif-containd breathiag apparatus is shown in Figure 72. Figure 7 1. MSA type masks, with positive-pressure air feed for the workcrs For the positive-pressure fxe masks, a supply of air can be met with comprcssed air in approved oxygen bottles, and with long connecter hoses to the face-rnasks. A 15-rn long hose gives the application crew the flexibility to spray over a Iarge area before the bottles need to be moved. Typicaiiy, the large canisters provide enough k h air for a number of shifts. Figure 72. SCBA: self-contained breathing apparatus
176 The initial testing by MIROC in 1990 examhed the cananbpsions of airbome toxicants associatad wîth poiyurahane applications [Archibalci, The toxicaras were idcntified as foltows: MDI: methylene bisphenyl iwqamte, generated 60m the isocysnrtc mixture Polyisocyanate: polymerized i~~cyanafe, generated hm the isocyanate mixture TEA: triethanolamine, cmated 6om the resin polyol mixaire Solid Polyurethane Partiailates: med 6om the formation of feaded isocyanate with resin Throughout the MIROC trials the Ministry of Labour (MOL) in Ontario condudeci air quality testing using midgeâ impingers. This method of testing forces bubbles of environmental air to pas through a solution The air is sampled at a rate of 1 Umin., as defined by NZOSH The solutions are analyzed by High Performance Liquid Chromatography and Ion Chromtography, for the concaitration of isocyanates and TEA, respectively. A second mehd of measuring the concentrations of isocyanate (MD0 was used during the MIROC tests, using an Autostep-925. This equipment samples and the concentrations of MD1 usïng cdourùnetnc stain sampling This method of sampling was shown to provide erroneous results such that h is recomrnended that the impinger method of testing be utilized for ail fùtwc sampling. Paiticulate tes&ing by MIROC uwig the asndrrd Cassella cyclone filter-type samplers. The guideüm due for gawral particulate ooncentrations is 10 mg/m3, as denned by the OHSA and ACGIH.
177 High partidate have been maansd when the ventil- nta at the locstioa of spraying ire vay high m, Due to thb pdaitiil heaith bazard, ït U the dation tubïhg be kcpt at minimum porsmity of 15 m to the spray d e. During the initial MIROC tating of the MUKguardN produci, wdergtound rem~~h spniy trials were performed at mine sites in Timrnins and Sudbury, Ontario [Archibald d. al., During these trials, air concentration measurrments of ucueacted M'DI and reac&ed polymerized isocyuuta were underuken by the Heaith and S.fi Support Services Branch of the Ontario Ministry of Labour. Concentration measurements utilized chexnid impingement rnonitors and liquid chromaîographic analysis of the reagent solutions. Unda the airrent Canadian regdation at the tirne of tecting, the time-weigkal average PA) ocaipotional exposufe amenoaion for MD1 cwiar ex& ppm (5 ppb) for an eight-hour &y and 401hour wak wedc [ACGIH, lm. The short-tenn arposure Lunit (SEL), or ceiling cxposure limt (CEC), cannot exceed 0-02 ppm (20 ppb). regulations for These are rrcommended by ACGUI (American Conferetlce of Governmental Industrial Hygienists) and are outlined in the OHSA (Ocaipationa1 Heaith & Safkty Act) hoqilute Monito~g at Kidd Cmck Mine, Timmins, Ontario In the first trial at the Kidd Creek Mine in Timmins, measurements of MD1 and polyisocyanates were d e directly at the spray source and at various locations downstream fiom spraying. In J I cases, concentrations were measured to be below the the-weighted lirnit exposure levels andor below detedzble limits. Specifiully, MD1 concentdons of 0.02 ppm were muaird at the site of spraying and no detectabk concentrations of polykocyanaîes wae detected at any otha locations up to 100 metres downsbeam h m the spraying site. The spray site wu ventilated a! the rate of 300 m3/min, with a resultant airflow velocity of 0.20 mis.
178 43-13 Air QmUy Tuthg it Copp Ciiff North Mioc, Jdy 1991 Average MD1 COlWXnQOfiOns ofo.02 ppm wae deâectd both at the rite of spraying and up to 15 metru d o m hm this site. At ail ouia domistrcom sampling sites, wndons wat obsecved to be bclow dekctable limits. The site was ventilated at the rate of 240 m'/min, muiting in an av- flow velocity of 0-20 ds At the second underground Mineguar- trial at Coppa ClXf North Mine, sampling was carried out to daetmine airbarne concentrations of isocyanate, triethanolamint and total dust during the application process wearwood, The back f~cc ud side 4 1 s of 2240 aossialf were sprayed with MineguarP over an area of 156 m2. Results of the air qurlity testirig indicated signifiant deatsses in the wmentdons of airborne contamhtion in the spray site, as compared to the fht underground trial at North Mine. In fact, there was a decrease in total dust particulaies by 41%, compared to the first spray, and al1 the sampling equipment remained uncoated during this second trial. Sarnpling wu conductrd in the 2240 cros-at, approximakly 6.1 mctres &om the spray site. The airfiow into the hadi was mcssured as 4,000 cfm Monitoring stations werc dm set up in the main North drift where 41,000 ch was recordeci and at the retuni air raise with 96,000 c h of air was being exhausted h m 2600 Level. The spraying time wu masurrd at 4.5 hours with a clearing time of approxïmately 40- minutes. Whm the application was complet+ the monitors were retrieved and a second series of samples were takm for the 40 minute clearing the.
179 Table 18. Air quality monitoring at CC North Mine, 1992 Tyeafwood, Site TDI MD1 HDI IPDI (mvd SQnying < ).0001 n Si 224ûxd 2240 x-ait TEA OP). <o,oo02 Althaugh the air quality report awiciuded that then was m over-exposure of wders to high conastmtions of MDI, it was recommended that seif-contained bmthhg apparatus continue to be used for d pasonne1 in the spray site. It was also indicaîed that the particulate Mst (MD0 can clog chunid Mlidge fe~~iratm dng them inappropriate d useless fm worka -on during MD1 exposure.
180 Air Qdty Monito~g at the Sudbury Neutrino Observatory, January 1993 Air quality testing was conducted at the Sudbury Neutrino Obsematory (SNO) in Januiuy of 1993, to detennine the airborne concentrations of methanolamine and isocyanates duhg applications of MineguardTM polyurechane [Burford, The spraying was carried out in the SN0 control drift on the 6800 Level at INCO's Creighton Mine. The mine site ventilation deparunent set up the monitors and collected the underground data. Eight Gilian HiFlow Sarnplers were set at flow rates of 1 Wmin. Four samplers were comected with duel impingers to test for isocyanaies. Two pumps, a single and a double, were set up in each of the four stations located downwind h m the spray site. Temperatures and humidity levels were manually measured and recorded every hour. The spraying was starteci at 9:30 am and lasted for almost 4 hours. The results of the monitoring are displayed in Table 19. TabIe 19. Air quality monitoring, - Sudbury Neutrino Observatory urford, Spray Site 1 m3a (ppm) IFDI (PPW Station B Station B Station C Station C Station D 1 0M)lO Station A Station A Station D Station B Station C Station B - at site I There were two exceedances for MDI, at Stations B and A, which were in the spray site and on the downwind side of the excavation. In these areas, al1 workers were wearing the required SCBA's (self-contained breathing apparatus). The ventilation flow in these areas was measured at 8,200 cfm in the control m m drift and 35,600 cfm in the mainline.
181 Ah Quriliw M it LNCO's Lower Cokmrn Mine, ï!b2 Thme MD1 midgd imphgers wac used to the 14s ofsùbomc i v within the air. At the spray locrrig the MD1 levels were above the TWA dowabk limit. The monitoring and anrlysis was conducted by AGRA Earth & Environmental Limited Air Qurlity Monitoring it INCO's Lower Cokman Mine, 1-t, 1993 During the appticatbn of MineguarcrY in the 19-dot top di, environmental monifors were instaiied to measure the airborne isocyanate concentrations in the rehun air-flow at different distances hm the tat site. The actuai underground MD1 monitoring was mntraaed to AGRA Earth & Emhmmd Limited. The MD1 testing was instigaîd for two main reasons: (1) to verifjr the levels of MDI ui the underground excavations during the MineguardP application and (2) to test the use of a water spray arrtun as a potait*l mechanism for neurraiizing the Pirbome imcyanaîes. Using the same procedure as the 20 dot teshg in 1992, five worbmm monitoring sîations (using rnidget irnpingcts) wac used during the hhegunp application, at di- of 0.3 m, 15 m, 30 m, 60 m and 120 m fiom the spray site. A tirne-weighted average orposure and the short-tam proasr concentdon of workas exposeci to Methykne Biphenyl Isocyuute (MDI) were ddamined h m the aivironmental monito~g shidy. The MD1 sampling was perfod fw each monitoring station and for both sides of a water autain [Edckson, 19941, with the results mmmmkd in the fobwing Figure 73-
182 Distance From 19-Slot Test Site [ml Figure 73. MD1 testing during 19 dot MineguardThf appl kat ion The air-flow, with any airborne MD1 particles, was dnwn througli the midgct inlpiiigers (containing an absorbing solution) at a specified flow rate for a known ciurdtion. Any èsisting MD1 particles were hydrolysed by the absorbing solution to forrn methylene dianil ine (LM DA) for subsequent quantification by colorimetric laboratory techniques. The imdi concentmtions measured at a distance of 30 m and 60 rn hm the 19 dot application site were reducrd and apparently affected by the water atomizer stations. From the environmentai tests underground, the use of the water curtain to neutnlizc airborne isocyanates appears to be siwcant; however, a controued laboralory test was reconirnended as a means to validate the field results. With further testing of the water atomizer station, as a method to contüin and neuii:ilizé the airbome isocyanates during spraying, and with research into alternative cfiemical coniaincis. it was concluded that Mineguard'fM is a highly feasible product for use in the mining industry-
183 Air Qdty Monitoring at PICO's Lower Cdemnn Mine, 3150 Ronip, 1993 During the application of the MineguardTM coating in the 3150 ramp test site, environmental testing was carried ou& to measure the levels of airbome isocyanates and to further test the effectiveness of the water curtain system. Five midget impinger monitoring devices were set up at varying distances down the ramp from the spray site at 0.3 a 15 m 30 m. 60 m and 122 m. respectively. The solutions were gathered and ana1yza.i at the completion of the spmying. Figure 74 indicates the MD1 concentrations (in ppm) for the 5 monitoring sites Distance fiwn Mi-rd Application Site [ml Figure 74. MD1 test results at various distances from a MineguardTM application site The MD1 concentration measured at a distance of 60 m fmm the access camp application site was Iikely reduced due to a dilution effect and due to the water atomizer station that was used to isolate the spray site. As with the previous testing results in 19 dot, a laboratory testing program was recornmended to verify the water cuitain effectiveness as a means to isolate the spmy sites. As a result, Iaboratory tests were initiateci by INCO to substanûate these fmdings.
184 Air Qurilitr Mombrhg at Imwcr Colcmam Miat 3370 Irvd, Mrirh 1996 Diphenylmdhlllt düsocyuute (MD0 monitoring wu aductcd at the mine de by INCO's Occupatid~~udErivirorunentDepartment~ Themonttonng place in the 22 aws-ait ast on 3370 Levd on March 12 and 13, * todc On March 13, the waiis of 22 cmss-cut East were sprayed with Mine- to height of appmximaîely 2.1 m and a disiuioe of 46 m. Five monitoring impingas were set up to cdlect the MD1 collcenfrzitions fiom the MineguarP spraying- There wae two aceedanas in the spray mne. Two wsta curtains were adivated during the application, which took 108 minutes. The writcr aptains were effêctive at reducing the aïhome concentrations of isocyanates to a level below the TWAEV. The tecornmendation fiom INCO's OHSE Dept was to continue to use the water Çurtain to contain the airbome isocyamtes. In addition, fùrther rnonito~g was suggested to &tain more data for a continued assessrnent of the effediveness of the water curtauis. All data at INCO is contained in the Ocaipationa1 Exposure Monitoring Program, to store and monitor the results Air Qudity Monitoring, McCrcedy East Mine, Hauiage Ramp, JUM 1996 Diphenylmethane düsocyuute (Mû0 monitoring was oonducteû st McCdy East Mine during the application ofmineguardn' in the main ramp wengeutte, The monitoring and spraying took place on June 28, 1996, during the mine's shutdown paiod. Positivepressure supplied air respiratocs were wom by al1 pasomel involved in the application- Pexsonal dety clothing included disposable coveralls and neopene gloves.
185 To Levack Mine Site 4175 x-cut Temperature = 28 OC Relative Humidity = 75% Carbon Monoxide = 7-ppm Cahn ikride. = 1 173Znnm Figure 75. Schematic plan of McCreedy East Mine, 153 haulage ramp with locations of MD1 sample sites and directions of airfiow The application of MineguardTM covered 370 mz dong the lower walis of the ramp (for a dismce of 125 m on each waii), with MD1 monitoring stations set-up downwind of the application, Figure 75. During the sprayhg, there were two exceedances within the spray zone for the total spraying time of approximately 45 minutes. An analysis of the monitoring data indicated that the MD1 concentrations were rapidly diluted in the rarnp axa, whereby aii downwind sarnplers verified negligible MD1 concentrations. Results from the monitoring are shown in Table 20, Table 20. MD1 monitoring, McCreedy East Mine, haulage ramp [Riengeutte, TWAEV for Tsocyanate (-NCO) = ppm Sarnple Description Time On Tm Off % TWAEV 1 Spray site 18:50 20:OO Spray site Before curtain :30 20:OO 20: < < 18.
186 Despite very high ventilation airtlows though the spray area. with a rate of 73,m c h the water cumin was activated for the entire application time. In fact, the recommendation h m the OHSE Dept at INCO was to continue to use the water curtains to contain exposures. In addition. OHSE requested that funher monitoring be conducted to ensure the reproducibility of the results and to obtah data for the purpose of an assessrnent Since the MineguardTM was used as a support product, the monitoring data was added to the Occupational Exposure Monitoring Pm- at M O Air Qualiîy Monitoring at Crean HiII Mine, December 1996 During an application of MineguardTM in the garage at Crean Hill Mine, diphenylmethane diisocyanate (MDI) monito~g was conducted by INCO1s OSE Dept. representative. The walls and back of the 3800 kvel maintenance area was spmyed with the polyurethane materid, over top of the existing bolrs and screen support. Ail personnel involved with the spray wore psi tive-pressure supplied air respirators with Full-face pieces. Ln addition, the applicators wore hooded disposable coveralls and neoprene gloves, The MD1 monitoring was conducted in the vicinity of the 3800 Level Garage, Figure 76. Airflow = 26,800cfm Temperature = 17.8 a C Relative Humidity = 63% Carbon Monoxide = 1 ppm Cabri Dio&de = 520 ppm Water Cumin Downwind Aiflow Figure 76, Schematic plan of Crean Hill 3800 level garage for MD1 monitoring with locations of MD1 sampling sites and directions of airflows
187 Ovsll~thacwaetwo~ceupationai~~rPPAPncesinthcgarage~y~Mdm~ acceedances. It was obscrved thrt the spray site bccsme satmated by a mist or bst 6Nig the spraying; thw poor Wibility was expaienced for the dustion of the sprayuig- recommendaîion h m the OHSE Dep rrpresentative was to continue to dud wod<rmm monitoring of MDI, which is the new responsibility of the plant or mine Ocaipationa1 Exposure Monitoring Program (OEMP) Coordinator. The MD1 monitoring dw is a new requifernent to Mtiîl the procedures outlined in the OEMP for the appiication ofmineguard or otha polyurrthpne dngs at INCO. As well. it was suggested t h ventilation airfiows k increased when visibility is poor during spraying Figure 77. A The MD1 monitoring results for the Crean Hill Mineguarbnr appiication is summarind in the foliowing Table 2 1. Table 2 1. MD1 monitoring results for Crean Hill Mine [Riengeutte, 1- TWAEV for Isocyanate (-NCO) = ppm Description Tihe On Time Off TWAEV Before Curtain 12: 13 14:OS
188 Figure 77. Overspray during MineguardTM application can cause poor visibility Sudbury Neutrino Observatory Wall Seaiing, March 1997 The final completion and sealing of the Sudbury Neutrino Observatory (Sm) with a polyurethane coating was undertaken in March The work was done successfully for: ( 1) the permanent ladderway, (2) an Alimrik elevator are% and (3) in the ramp bulkhead on the floor of the cavity. The sealing pmess involveci removal or cutting of any anchoring steel in the wd, par& with a non-shnnk grout, and applying several coats of a polyurethane product to build up the final coating thickness to a minimum of 7-5 mm. in order to protect delicitte instruments already installed in the cavity region, tqaulin enclosures were built for each of the above mentioned spray areas. A separate ventilation fan was installed for the sprayîng, with appmximately 1,SOO c h of air exhausting to a point 10 m past the cavity entrante. During the polyurethane spraying, the isocyanate levels were monitored both outside and inside the enclosure areas. Air supply respirators were used by the personnel inside the enclosure d u ~ the g spnying proces.
189 C t The colounmaric mommmg indicated isocyanatc kvels abon the rrcommaded TLV of pprn when the s~raying was taking place For example, for the 80 minute spray îime in the Alirnak a peak isocyanate c~llcentration of pprn was deteded in fjtcf the TLV was ex& within 4 minutes fkom the start of spraying in the Ali& el- site. The spraying in the laâdmmy did not produce airbome isocyanate greater than the TLV for the aitirt 4û-minutes ofspraying. The bulkhead spraying ducted on Uarch 6, required spraying for 62 minutes. This site reached isocyanate levels above the TLV, with a peak concenerabon of p p The TLV was exceeded within 10 minutes âom the star& of sp~ayuil3- A post-spray analysis of the data m a n and Oliver, suggests thaî a clearance tirne of 5-minutes was required to clear the air (with isqanate levels < 0.05 pprn). This was the îhe necessary to duce the isocyanates fkom ppm to below the TLV. Of course, this time fiame is relative to the given exhaus rate and the size of the enclosure (23 m cross section by 35 m in height). Outside the enclosures, the monitoring indicated no d etdle Ievels of isocyanates Air Qu* Monitoring at INCO's Copper Lliff South Mine, 1997 The c o d o n of ùrbonie isocyanates were m d at Copper Cliff South Mine ducing an application of Min- within a large top dl. These tests were mnducted by the CC. South Mine ventiiation departmnt personnel, with analysis by INCO's Process Thlogy Department.
190 In.ddrtionto~&duripriiail.temomtoringwu~&mwGidnOmthcrpnySae: (1) m the vicinity of the spraying, in the miin uicey raoss h m the 7050 thaâue~(rbaiti(knkhmthespfayarrton),md(3) towifdthe~* (2) at app mimately 10-m afk the wrta autain nie teyting indid negligible levels ofmdi in the aidow. The details of the PIztiCulptt tedng is shown in Tabk 22. Table 22. Particutaie dust sampling at CC South Mine in 1997 From these results, it appears as if the water autain did not inhibit transport of respirable dust through the water mist- Furthermore, since the MD1 rdts were dl negligiile, th= were m obvious conchrsions to rnake regarding the effkctiveness of the water airtalli in knocking down Pirbome isocyanatcs. One positive conclusion is the asmmnce of g d air quality? Born a concentration of isocyonates and respirable dust view-point Air Qudity Monito~g at McCdy East Mine, 1998 From an occupationrl health and safi view-point, the application of MineguarP in the narrow vein stopes experienced an unusual phenornena - dust. More spedjcally, the application genetated a thick, white, mist-liie dust The dust would graduaily appear, jus& moments &er the spraying commenceci, filling the dope area and the main acccss heading (that was located downwind h m the spray site). The dust d o n was consistent with every application. Ma the fht spray, when the dust was noticed, the mine's ventilation experts were called in for monitoring and testing. Sampl8-train particuke monitoring indicated that the dusi was a cubon mitaial with quantitia of inhrlable portiatlates that ex& the TLV (Threshold Lirnit Value) TWA rie Weighted Average) of > 10 mg/m3 for an 8 hour workday and 40 hour wmhmdq [ACGM,
191 (1) inadequate volumes of wiitcruraigb the wdta aimin, (2) high humidity and excessive tanpaaaire efei (3) excessive airfiow at the spray site, (4) close proxirnîty of ventilation tubing and airflow to the spray-gun/operator, (5) inefficient mwng of the polyurethane liquids at the mzzle- The dust ueation has Id to fidm research, to be undertaken by NO'S Mines Research Department in A tes& plocedure has been designecl with an objective ofce-c~eating the dust phenornenon thaî cxisted at McCrdy East Mine. In sumrnary, a smd test drift at the 175 Orebody will be sprayed with a p o l ~ materiai, with high airflow velocities bm a nearby ventilation duct. In addition, various water airtain scenarios d l be tested, alone and in combination with the hi& velocity andior close proximity ventilation Particle monitoting devices will be used, to record the levels of nuisance dust (iiable and respirsble) dong with a selection dut-suppression water-!wray=. The dusi suppression testing is an extaision of the initial test, to investigate potaisul methods of controhg dut. This caim well be important infodon for any fbture applications where there may bc Iittlc option for altering the ventilation system, etc., and wbere dust aeaîion is again Howwer, the main aim of the msearch is identiq the cause of dust, in order to generatc prxxdures for diminating dust creasion in future liner applications.
192 Lis worthnotingthaturmirûc~ ideatifieddustpomcm ~uiiapplicaticm &CC North M I (refa to Ssdion 1 of this document)- The MIROC repts cite the cause of the dust h m the ventilation. In mc application, the nuon fa dust was said to be due to high ventilation rates, while lncrba application's chut problan was ddaminod to k h m inadquate ventilation pobkms. ExpericnceaîINCOkdraieto~wah~firstcxpluirtion 'ïhisisreinfdbythe description ofthe spray site conditions at McCreedy East Mine by the mzzle operatar "P was odremelyhotandwindyinthchadi... itwaswrtahimune"[corbeqpcraarnmin, It is hypoth&d thrit the high velocity airflow (in ciose proxhky to the spraying) causes the liquid stnun hm the gun to be blown out and away ibn the rock surnice, into the general aîmosphere. Bacouwe of the rapd set-time of the chernicals, the sprayed Iiquids are auing within the air as smali dust particles, rether than being dirtded immediately onto the rock surfàce to becorne a cured amtins This postuiation wilt be firlly tesied in the INCO Research Mine Air Qurlity Monito~g at Junction Mint, A u s e 1998 At the Jundion Mue in Ausinüa, monitoring of the airborne i~0~~8118fes was conducteci during underground applications ofmineguard'w. The air quality sampling was taken in the development heading to test the level of isocyanates and to test the effediveness of the water airtaùi during the application. The mining regulations for western Australia state that the Time Weighted Average WA) exposwe for isocyanates is 20 &m3 (for an 8 hour period) and the Short T m Exposure LiMt (STEL) is 70 wm3 (over a 15 minute intend). Table 23 is a summary of the air quality testing at JUtiCtion Mine, WA Note that there are high levels of airborne isocyanates in the immediate vicinity of the applidon, with a dropoff within 15 m from the spray site. The recailts indicaîe the deaiveness of the wiia axtain in neutralizing the isocyanates and isolating the application area 60m the mnabk of the mine.
193 Tabit 23. Air quaiity test rtsults for MineguarP application at the Junction Mine, WA [Fm et. al., Drift Waii insi& Water CurtPin Drift Wall insi& Watercurtain Drift Wall outside Waîer Cwtain I The ability to contain and neutdk airborne isocyanafes would gredy enhance the acceptance of M i n e for underground use. In fia, the abiiity to arsure that the airborne isocyanate particles are not carried into the main airstrearn to barefaced workers in the mine environment is in an Engineering Contrd System for use ofpdyurrthme gound suppott Accordhg to the OHSA Regdations for Isocyanates, 1983, the "employer shall take al1 necesary mtasures and procedures by means of enguiecring contrds, work practîces and hygieme pnaices and fdities" to ensure the imqmatc COCK;entCBtio~ls are reduced to the lowest praaicai level (and not ex& the TLV and TWAEV). With the MOL requiremcnts in min& INCO Mine Research explored the -ai of ushg a water autain (similar to the water systems used to aippress dust with shotuete appiicati-) to d i z e airborne isocyanates. The principle of this method is to itomzc wrta decules (&O) ud produce a finc spray. This spray mil crea!e an envebpe in which iirbonw contaminate (jsocyanate) mist dides, yielding twa d tant companerrts: carbon dioxide gas and a solid urea particle (Equation 2).
194 Using the shotcrete water scnibber design as a template, a new water misting system was developed and tested underground af INCO with MineguardM applications. The tests were designed to determine the effectiveness of the water curtain (with a very fine mist of atomized water particles) in neutraiizing airborne isocyanates. The water curtain, as designed at INCO Witz, 19991, consists of atomizing nozzles that ae attached to a rubber hose in 1-metre increments. The ends of the hose are fitted with vaives and connectors, to hook-up to the underground water lines, to provide water inflow from one or both ends of the hose (depending on the size of the drift opening). For each underground application, the hose-and-atomizer system (tenned: water cumin) is tied to the back and walis of the heading to fom a full one of water spny. For al1 application sites, the water cunain is installed in,the ventilation ai~~ay at one or more downstream locations away h m the polyurethane spray site. It is not deemed necessary to place water cumins upstrearn from the spray sites since a sufficient aùflow will inhibit the travel of the isocyanates upwind. Instead, INCO's practice is to insu a double-barricade and a "MineguardTM Spray Site - A uthod Personnel Only" sign approximately 15-m upwind from the spray site. This prevents workers h m inadvertently wandering into the spray site without the appropriate breathing apparatus. Each atomizer is capabie of producing a mist over a 120-degree spray radius. The 1-m spacing dong the hose aiiows the nozzle sprays to intemct together and create a fulicoverage of mist across the underground excavation. A photo of the atomizer is show in Figure 78. Figure 78. Water spray nozzle (or aiomizer) on the spray hose
195 Lab tests of the water spray curtain dediveness, in c m j d with Queen's University (Müüng Department) and Uryion Plasb'cs Inc. were initiatexi by INCO to validate the field results. The MDI c011ection and andysis was contracted to AGRA Earth & Environmental Limited, with design and cation of the test tunnel and pumping systern by Queen's University, Mining Enginaring Department. Reports summariting the test pocedure and the MDT d t s were provideci to INCO [Archibdd & Lausch, lm, respectively. The a d testing was performed in November 1995 at the spray booth fàciiities of Uryllon Plastics Inc. in Guelph Ontario. INCO's -ve was on site for co-ordination of the project. A pseudodrift, representative of typical underground dimensions far exploration headings, was fàbricated out of plywd sheers with steel channel waii Shi&. The inside of the tume1 was lined with 0.15 mm thick PVC plastic. The overall tunnel dimensions were 2.5 m wide by 2.5 rn high and approximately 10 m long This Iengîh of twuiel was required in orda to prevent turbulence at the mid-tunnel position where the water saubbers were uistalled. The MkgurP spraying ad aivironmentai monitoring were cmkd out inside the tunnel. The prefhricated tunnel was erected within the existing spray booth iû Uqlon, dong with a plastic sh~ing and pumping system for capturing and diminaihg the wota pduced hm the water curtains. A schernatic of the test tunnel with the locations of the water sprayas is shown in Figure 79.
196 - Cunains 25- Moi Air Infiow w Test Tunnel Figure 79. Schematic of the test tunnel, with locations of MD1 monitoa and water curtains The isocyanate monitors were placed at three locations, for continuous monitoring dunng the spraying. In reference to Figure 79 (above), the MD1 monitors were located as follows: ( 1 ) in the rniddle of the test tunnel, immediately before the water curtauis, (2) at the rear of the test tunnel, with 10 m between the sprayer and the monitoring unit, (3) in the spray booth's exhaust stack. A photo looking inside the test tunnel is depicted in the following Figure 80. The actud polyurethane application was conducted at the entrance to the tunnel such that the aimow would carry any airborne isocyanates through the water scrubbing system.
197 Figure 80. View looking inside the spray tunnel for isocyanate monitoring photo Courtesy of Dr. I. Archibald, Queen's University]. The isocyanate monitoring and airflow velocities at the three tunnel sites were conducted continuously throughout the MineguardTM spraying tests. In total, four airflow configurations were used for the testing, as outlined in Table 24, with measurements taken manually, Figure 8 1, Table 24. Summary of ventilation flow conditions [Archibald and Lausch, Ai rflow Veloci ty ( ds) Test 1 Ventilation. Air Temperature 1 1 I Entrance 1 Cu- 1 Exhaust 1 & Relative Humidity ~oaimow 1 No measurements taken. I1S0C % " 0 pulley 2.5" 0 pulley O O C 15 C 15 C 25% 25% 25% I For ventilation during the polyurethme application, the spray booth was already equipped with an exhaust fan network with a capacity for 14,000 cfm (397 m3/min). For the given cross-sectional area of the booth itself, the regulated average airflow rate was predicted to approximate 146 Cpm (0.74 ds), which was Lower than rates previously met during typical in-situ opemtions at INCO.
198 Figure 81. Akfiow velocity measurements being taken in the spray tunnel [Photo Courtesy of Dr. J. Archibdd, Queen's University] For each of the four ventilation flow conditions, two water curtain tests were conducted: 1. - with one warer curtain operating and with Mineguardnf spraying for 15 minutes 2. - with two water cumins operating and with MineguardTM spraying for 20 minutes In total, 140-minutes was spent spraying Mineguardm while MD1 concentrations were. measured. Approximately % of a drum-set of materials was consumed for the trial (Le. 150 L of isocyanates and 150 L of polyol resin). Qualitative assessments were made of the water curtain flow rates, by cornparhg the rate of pump discharge from the sump versus the volume of water collected in the sump. More specifically, with one curtain in operation, the level of water in the sump slowly decreased during spraying. In essence, the rate of water inflow hm the water curtain was less than the rate of water pumping hm the sump. Comparatively, the water level increased slowly when two water curtains were in operation for the second series of tests. This implies that the rate of water inflow from the two curtains was higher than the discharge pumping rate at the sump. For the environmental testing, the data was collected and analyzed in order to evaluate airbome mist concentrations of MD1 under conuoiled tunnel conditions Erickson, According to the report to inco, a mist is a suspension of small liquid droplets in the air.
199 Mists are fonned in the wwlrplace by operations that involve sprayhg wch as p y painting or the application of polyursthonab.scd poduds. The shdy f d on the air quality condiiions undatk eight test d s, as dcsaibed Ibove. The terms of refetmct fa the environmentai dysis wae brsad on- (1) regdatory guidelines, and (2) sampling mahodr and analyticd mc(hodq as defineci by MOL, Occupationai Health & Slfety Division (OSHA) and the Nttiod LNtia>ie for Occupational Safkây & Health (NIOSH), respcaivelycly. n>e raits wae intecpd and compared to provincial and intenutionrl legi*slativt guidelines (for 1995). In reference to the MOL Regulation 455/83 respeding isocyamtes, the sampling rneîhoâ involves the bubbling a known volume of air at a ked rate thnwgh a midget Mpinga (borosilicate) containhg an absorbing solution. For this testing, four HI&-Flow siamplers were used (3-Gilian and 1-Alpha back-up). The samples wae analyzed using the EPA mettiod 625/827û- solvent extractiodgas chrornatographhass spectrometer. As taken fiom the report to INCO [Erickson, 1996), the results of the testing are surnmarized hereunk (1) Al1 airborne concentrasions of MD1 were below the MOL'S ceiling exposure value (0.02 ppm) except for one sample. (2) The high concentration sample ( > 0.02 ppm ) was colleded during spray trial #2 and represents the worst-case scenario (i-e. no water autain in operation and negligible air velocity through the tunnel). (3) Simulated ventilation conditions indicated sufficient air volumes to adequately mix and dilute any unreacted airborne isocyanate WI) contaminants. (4) Spray trials #3 and 4 indicated that the use of the water airtain successfiilly reduced airborne MD1 concentrations by appmximately 9û% when the two autains were in operat ion,
200 (5) The data indiutes thaî the implementation of wrta aimih< is a succeshi mechanism to duce umeactd.irb<nne isocyamîe col~i~lltrrtntio The The ac& to isolate the spray site ud inhibit the trader of.irbomc iaocyuutc (MD0 to d&r wuxk p h in the underground (6) Post-spray monitoring (24-horP paiod) withlli the test tunnel indi4 MD1 concentrations above the MOL's TWAEV (0.05 ppm) but less than the MOL's CEL (0.02 ppm). (7) The tu~el test mults do not m l y rcgtesent the dydunic conditions acperienced in the underground mining environment AGRA also provided INCO with information relating to Dilution Ventilation. This is the practice of diluting contaminatcd air with uncontaminated air fm the purpose of controliing potential airborne Mth hazards. Dilution Ventilation is not as effective as Local Exhaust Ventilation A material balance equation muation 4) was provided by AGRA for the calailation of ventilation capacities to dilute MD1 airborne mists to steady s&te concentrations. Q=((403 x 106 ~~?~~)XSGXERXK/MW)/CEL (Equation 4) Q = actual ventilation rote (flhin) SG = specific gravity ER = evapraîion rate (pts/min) K = fiidor for incornpiete mixing MW = molecular weight of volatile liquid (ppm) CEL = cciling exposure limit (ppm for the TWAEV) For MDI: SG= 1.15 ER= l.4x 'C K = 8 (far underground) MW = CEL = 0.02 pprn
201 This equation can be usai by ventilation departmen& to consider the ncauiry ventü.tion requirements in a MinegUPdn spiy site (or the main line coanccting to a spray site). This equation 4 assumes that (1) the quantity ofthe contuninont is rot tao great or imprîctical for dilution; (2) wodcm ue fâr cnough away h m the spray site to pvat wodccrs being exposed to dues above the CEL; (3) the toxicity of the contomi~lrt is bw, ad; (4) the evolution of the contaminant is uniform. Further to these results, AGRA made some recommendations fm firrther work: (1) In accordance with Ontario Regdation 455/83, a written assessm«rt should be conducted to detennine which workers are expased to iqanates. This assessrnent shld be conducted by the employer or representative at N O. (2) The assessrnent process may determine that an isocyanate control program is necessary for INCO. Such a coml program wwld include provisions for engineering controlg work pradiceo, hygiene practices and faülitics, air monitoring, reccd keeping and medical surveillance. in addition, the regulation requires a training program for supervisors and workers on the health effects of isocyanates and the provisions of the control program. (3) Additional underground monitoring is recomrnended, to fiinher assess the health and safety issues related to the increased spraying of the polyurethane product. The lab testing dernonstraîed the efeectiveness of the water mist arrtain for isolahg the released MD1 wmponent to areas local to the spray site. Atthough mt cldy ideded in the test results, it is also postulateci that a slower air velocity in the spray site is ptefmed to higher airflows.
202 In theory, the reduced air vebcity d d Jlow for the Urbonie isocy.nstes to beoow exposed to the wsta particles fa a longer time paiod ud haice, for gr- rrduction in airborne contaminanu o. This Scpothesis may be worth fiirthcr examhtion. As a direct mlt of the Lb tesîing a d h m fiiriha unâ- MDï monitoring, dl MineguarP applications a INCO mut use the wita d n, as defined in INCO's und-d operatiord poadures. Only personnei within designrted spray sites, which are confined by wpa airtuar at dl entrana po* full-face breaîhing rpprrtw during spraying of mus wear positive pressure, Al1 other pasonnei within the mine are wnsidaed d e h m inadvaient releases of airbome isocyanatc matmals. As part of the irnpiementation pojea for spray-on Iina support at INCO, the otepr have been taken to meet the requkements for MOL'S Regulation 455/83. As of 1996, INCO has completed an isoçyanate assessment. As wd, the monitoring data for MD1 concentrations continues to be c o U d by MC0 personnel dunng dl applications of poiyurethanes in the Onîarb Division mines. Al1 tcjting data is rrcaded in a Dmsbwide database, and ail workaj involved in the application of polyufethane are on a medical sweillance program with noorcl-kwg log books at each site. DetPils of INC07s irnplementation project a d the establishai proosdures are outlined in the foiiowing section The irnplementation of MineguarP into the INCO mines has involved personnel hm a number of speciaity areas and positions: Mines Research, Gnwd ConW Operaîions, Management, OcarpOtional Heaith, Saféty and Environment, Vaaüa!jon, Worker Representatives, Muntcnure, ad Dewelopmeni Minas. in addition, assistance has been added fkom the equipmcnt supplia5 matmal mpnifichinrs ud the application experts- As part of the Implementath Plan at INCOS thc Ocatpaîional Heaith, Safety and Environment Deparünent (OSFIE) hm rwid the MkgmmP producf with an undastsnding that ür's pdud d d Division. k used at any of the plants (suifaoe and underground) within the On-
203 Asrequuedforanyduignaîd substuice, INCOhasdhardto theregdations ptatbythc Mini~ey of Labour (-0). The maximum TWAEV errpoa~c ievel as stipdatd by the MOL for isocyanaîes (-NCO) U parts pa million Note that these guidelines and dety precautionsonlybax>ni.parinmwhcnthac~eparwncl inthevicinityofîhespray Ute. ui the case ofan autocnrted mine, themecf fiu~prayairt4ins andventdation rites bacoms W~ the isocyanates in mind, detaiied transportation, storage Md application prdures have been developed by NO. In addition, both interd and extemal consultants have been retaid to conduct air testing programs. As a result of the testing, a water misting asrtain has been proven mccessfùl for isolating air-borne i-es within the sptaying site and for ùihibiting unîllowable air-borne isocyanate arposures, of TWAEV < 5 ppb, to other workers in the mines. AU pasons within the INCO spray sites are fit-tested and tnined to use selfantained brrathing apparatus tliroughout the sprayhg process. The water curtain and the positive-pressure masks ensure that no d e r is srposeci to intolerable levels of air-bonie isocyanates of TWAEV > Sppb. For transportation of the Mi- chemicals, then is m risk of inhalation of isocyanates > Sppb by workers since the maximum isocyanate levels are only released d d g the spraying process. In üquid form, the isocyanates used in Mineguardnr am much less volatile than water, and in solid form, the MineguarV liner does not contain isocyanates- The chernical reaaion of resin and isocyanafes results in an inert Coafing. INCO's research has concluded that a second c&g of Mineguardnr with a venniculite dust is not required for mdapmd use. Initial rrsearch fiom Qwen's University aiggested a need for the second corting with nnnicuiite, as a bretarding &a [Archibald, rnd Fl-,
204 Based on the reaaivity of tht isocyuiate liquid with woter, somt conbol measmes cari be implemented for piasding worlcas 6iom Liquid isocyanates as a rcsult of a spill a d airborne isocyanates during spraying: 1. EquipmedGau Decontamin ation: - work or shifl For ijocyanates, the decontaminants include: (1) a mixîure of water (90-95%), sodium carbonate (5-1%) and liquid detergent (0.2-OS%), and (2) nonflammable materials (sand, china clay or sawdust), which is usefiil to ab& and neutralize MDL hiring an application of p o l it is ~ important to use decontamk&s for - - neutralituig isocyamte residue within equipment and gear at the completion of the 2. Transportation I Handling of Spilis: Al1 spills of the liquid isocyanate can be effectiveiy controlled with decontaminants (see above) what MD1 is absorbed with conventional absorbents and then neutralized by pouring wata ont0 the affeded site. Due to the low volatility of the isocyanates in the liquid fw negligible levels of airborne isocyanates are created at a spill site. Transportation 1 handling personnel at the spill site are p-ed fkom these low levels of airborne particles with the use of aganic vapour ~spinton. AU otha personnel in the immediate vicinity of the spi11 need only retreat upwind ikom the site until the liquid is neuaril'd. The chernical reacîion of the isocyanate liquid with water WU occur in less than 15 minutes. S i the reaction ofmdi with water m e s C a gas, it is important nd to aüow water and MDI to rnix within a closed drudcontaina. This can lead to excessive presure and possible bursting or mpture of the ddcontainer.
205 3. water Spray Curtria: -onbbeawne ~~ycoriccnsnted8surbonw~~thc spraying pmabrr. A niisting of wrier (a amtain) can &dveiy isok the Minegurrdn~ysitewhaebyisocyllllteparticlcsuc~wahuithe~y area and m areas downwind of the wates CUCtPin contain high concentrotioii9 of the isocyanate puticle. L.bor*ay and undcrgroud isocyuute testing at INCû has indicated the desdivcntss of the misting autain to knock &wn sirborne imqamtes at the airtaùi location to weu bebw the -le level of two parts-per-b'illion. This waterairt4uiwnngmmtrrllowstheminllig~tocontinue m p t a d while spraying urdaground and all Pssocieted personnet to hly move thrclughout the mine without threat of inhaling airborne isocyanate amcentratioris. The spray site is completely isolated in the mine and pratedion is pmvided to perso~el in the site with fùu-face positive presswe breathuig apparatus. 4. Empty Dnum Disposal: Ernpty dnuns of isocyanate (Part A) will contain trace amounts of the isocyanate liquid. The MD1 is Cffêctiveiy neutralized by addiig wpta (with some sodium carbonate and liquid detergent) to the dnims. Due to the aeation of COI gas, the bung hole in the mer-filled d m shouid not be re-sealed for at leasî 24 hwrs der filling, othenivise thc drum could becorne pressunted. Once decontaminated, the pduct d m s should never be reused unless the drums have bccn "ceconditioned" by a certified company. 5. Disposal of Liquid IsocyaMtes: For disposal of small quantities ofisocy~~te üquid, the following is fec~mmended: OR Add excess resin polyol to the isocyanate cesidue to diow for a cornpletc reaction. Ensure the work site has adquate ventilation or use a supplied air fespifator for this procedure.
206 Add the solution (ofwater9-uuiium csrbomte and liquid ment) to the isocyuiotes with a mtio of 103 by volume Do nd a d the d m for r paiodofatler*24hairs. Eirryetheareabwelivaitüated. Disposeofthe alkaline sohition ud drums in iwcordpuwx with oppropnot+ regukhu. Before transportath and handling of MineguarP on any INCO pro-, information must be on-hand and must be reviewd by au relevant perso~ei. the MSDS During spraying of MineguardrY, all personnel mua wear some additionel protedive personnel gear tht includes: latex gloves, protedive gloves, disposable covds and positive-pressurt breothing apparatus (fùll-face mask with hciok-ups to oxygen tanks via air hoses). At INCO? the air masks are the MSA brand. NIOSH reoomrnends preplacement and periodic medical surveillance pmgrams for any.. workers potentially exposed to Preplacement and annual examinati should consist of (1) medical and work histories with emphasis on respiratory ador allergie conditions, (2) a physicat exam that centers on the respiratory tract, (3) a pulmonw tiinction test and (4) a review whether the worker is able to Wear a supplieci-air res~iratm. OClS In accordance with the NIOSH tec~mmendations, any personnel involved in the application of MineguarP within INCO mut first undergo a medical examination. Upon acceptance of health, esdi opera,tor is phcd on a mdical su~illance program, whaeby the general health of the worker is monitd on an annual basis. The medical cec~rds are r&id for 20 to 40 y- as per the Occupational Heaith & S afi Act Regulations and Requirements.
207 Environmental tes&ing should be performed duririg the appiic;itioti of v, as determined by the mine's enginsaing &ptment Uajor teshg uiclude~ worboom and downwurd hcyamk (MD0 monitoring using midget impingers to cnsure fiwtionaiity of the water airtaui sprays f8r isolating airbonie isocyanates fiom dl mine workers. Other environmental tests, such as gas sampling or dust sampiing, can be conduded at the discfelion of the mine. For aïrbome isocyamüe monitoring, impingers should be set up in the wockrwm and on the downwind side of the wgta antain. Additiorial airborme kcyamtc monitoring sites coukl be set up fbrther bwnwind, as wouid be suggested by the mine's ventilation deparunent. These additional rdmgs d l provide an undersbnding of the ventilation dilution effects on any isocyanates and to negligibfe or indistinguishable levels in the mine's main air Stream. Each spray site will have unique drift / geome~ry parameters *ch will efféct the ventilation (velocities and volumes)- Subsequently, the site ctuuacteristics and ventilation flows d l effbct the concentrations of airborne isocyanates (the dilution effkts)- Ali spray site -ers need to be considered when arranging for the MIN test sites and the location of uie water clum(s). The nurnber of isocyanate tests to perform for each spray site should be detennined by the ventilation department, in consultation with fecormnendations by the OHSE The testing n d not be repeated for each application of Minegrrarbu in the site. In $4 the ventilation depumwm can rrcommend a statïsticaüy meaningnil nurnber of tests to pafm for a series of applications in a site. This is a site specific and individual mine decision.
208 The initial air quality testhg by MIROC, wiîh qmmtativcs fiun the Mjnistry of Labour.. th& (Oiitario)7has~LvkAthrrdiaeisnosi~~cbcmicrl~ exhm during oraffathe appücrtionofthc p dyurdtrpnev; this assumes the application ocairs with the standard mhe air ventilation conid Wergunst, Since the initial MIROC tests, additional detailed air quality tests have been umducted in conjunction with the undergnwd spray trials and support assesment. In an analysis of the test the airbonie chernical contamination hazard &sts d y at the spray site. airborne MDI is isolated within the site with the use of the water spray autains- This has been substantiaîeû with Womîocy and fiirtha underground testin& Each wwker in the spray site is prdected fiom MD1 by wearing a selfkontained breathùig apparatus and safi clothing: M e d disposable covefaus and neopme gloves. AU workers in the mine are protedecl fiom airborne MD1 with the use of the watcr spray autain and with adquate d ation fm dilution of chernical contaminaiion High cancentrations of respirable and inhalable dusc have been observed at only two sites: McCreedy East Nmw Vein and Copper CWNorth MineMùie The dust is believed to be associated with extremely high airtlow velocities d i at the sprayer. Future work will involve controliied testing to aeate dust, and testing of Engked Controls for suppressing the concentrations, ive. a control method cannot be developed untii the situation is reaeateed. AU produres and protocols for the use of polywethanc spray-on products have been kloped and irnplemented at INC07 Ontario Division With appropriaîe handling, transportatig and application, the product does not pose a Mth risk to the workexs. The
209 The MineguardN matad has ban specidly devdopsd ud rmm&du& hr the mining indu- for use udqpud- In its Onginai fbm, the liquid compom* parts of MineguarcP are ducrii as haviag high fluh points d am therefbre not nwmolly considered as flarnmable Howcveu, sorne polyurahpnes may bum if heated dficientiy. Sorne types of irrocyuutc involveci in a fire ml1 erolve fima in highîy toxic mnccnîdons; the bazardous off-&mu inclde the oxida of arbon.od nitrogen ud trrces of hydrogai cyanide (HCN). Full emergency apipmcnt diould bc worn by paso& ùivolved in =ch fie incidents; the use of seif-contained breaîhing apparatus is essential. Hydrogen cyanide is a colourless gas that is poisonous through inhalation, ingestion, and skin absorption The threshold limit value WV) is recommended as 10 ppm and the maximum allowable concentdon for the tirne-weighted average (MAC-TWA) is 20 ppm [ACGIH, A concenîmîion of HCN of > 280 ppm is irnmediately fatal. HCN is encountered during its rnanufàcture as a reagent and in the production of chernical intermediates for the manufacture of synthetic fibres, plastics etc. It is usefiil as a fumigation product, and may be generafed during electroplating, photographie development, and refhing of petroleum. HCN is also released during buming of wood and plastics. In fa* HCN will be produced during the combustion of any nitrogenumtaining organic compainds, both natural and synthetic. The amount of HCN produced fiom these maîerials will generally incrrasc as the combustion tempemure is increaseû, especially above 600' C. The actual arnount of HCN prtsent in the smoke, howevr, will Vary since most of the HCN itself will bum in the fire if sufficient air is available. Under similar fire conditions, polyurethane foams pduce les HCN than wool, nylon and other textiles commonly used for fùrnishings. Toxic gases hm polyurethane foam and wood fires are shown, Table 25. Table 25. Toxic gases fiom polyurethane and plywood [Woods, 19871
210 Wi the off-gas know1edge in mie the prochrd wu devebped with additional chemids, usai as dditivcq in the min mix. This hr haiha rrduad the liner's tlunmbility potaiti.l, as indicatd on tk poduct MSDS wrybn, whereby MineguanP is classifid as non-combustible. Even with the nokcornôush'ble rating and with the extensive flame teshg by MIROC and Queen's University [Archibald, 19911, there is a misconception within the mining industry that the polyurerhane produa poses a serious fïre hauud. This belief is likely a result of the publicized problems with polyurcthane fmms and their flammability. Due to a polyurelhant farmr fire in South Mca, the Canadian mining industry has viewed all polyurethane material with caution The fire at the Kinross Mine, SA, resulted in the deaths of 177 underground miners in These miners were Wed h m inhalation of hatardous fûmes (hydrogen cyanide) released by the buming pdyurethane fmm. Other polyurethane foam fire catastrophes include the death of nine miners at the Michael Colliery in Scotland in 1968 and the deah of seven minas at Western Deep Levels in South Afiica in As a result of these fatalities, polyurethane foam has been banned for underground use in bath the UK and the Republic of South Mca ML, Within Canada, the most recent polyurethane foam fire prompteci the publication of a Hezetd Alert from the MOL. The foarn was king used as fiil stopping and was somehow ignited. The mine resaie tearns had diaailty approaching the f k due to thick smoke and the presence of hydrogen cyanide gases The poiyufethane coasuig utilized in South Mca and the fm fiu used in Canada iacked any type of fire retardant withui its mix to pcwent combustion In addition, these polyurethane matends were faûmf. as opposed to a nc~n-ceilular liner, and once combustion is initiatad the fire repidly spreads.
211 The MkgunP probec has 1 flame Jpnad rathg (as per ASTM E-84 testuig pocedures) that is sufl6cient for use mckgmnd. A new pdyurethpne Qrodud hm Futurii Chhgs (Rdcguar~ has the hi- liners for mining. Althou* fhme spcead rating of aü plyumihm or pdyurtp hybrïd both products have high flarne resistance, the MkguanP may tend to melt and dnp whcn cxposed to the flame source. This d d potentially be a crmceni where MineguarP could rnelt and drip fiom the back of a headig (iiîhe liner is exposed to a flame souce). In some ment teshg Darboe, 19981, the drips fiom the MineguardN produa are "apparently buming as they Hl". The RoclrguarrlrY, with higher fire resistant properties (ASTM E-84, Class l), does not melt or propaga!e du~g exposure to direct flame. Despite the ackmwledged drip potential, both MineguarP and R o c k m polyurethane and polyurea materials have been sufficiently tested and approved for underground use. The initial testing of the MineguarCTM's flammability was anduded by Queen's University, under a contrad to MIROC [Archiid, During one of the eariiest MIROC -ch phases, comprehensive review of MUieguarP flammability potential was undertaken. In one series of trials, MineguarP was subjeded to various diuect flame sources and its potential flamrnability was assessed. Two of the flame sources used comprised a Bunsen gas torch (darne tan- of 48&SûOo C) d a high velocïty propone gas torch (flame temperature of ' C). A summary of the results is presented in Section 1 of this thesis doaiment, as derived fiom the MIROC reports [Archibald, 19911, fw fiame tests on rock and cement board surfhes. AdditKnial - - Flame Tunnel Tests were aiso conducted on the MineguarcP pduds for a Flame Spread Raîing.
212 In no cases did any of the mataiais, fôilowing cxposuft to tlame and physid degradatiors ever continue to bwn when the fiame wce was removeci h m d i contact. The only condition under which apparent Mineguardriw degradation ocamed m k place when flame.. contact was mauitnuied at a sipificantly high tempaaturr P78Om C) for long time intwls. Under such cond'ions, MUieguarbcY will physically decompose (i.e liquee) but will nût stlsfcahjhme. This means that the MineguardP liner wiil decompose only where there is an intense fire in d i contact with the liner- For example, a buming scoop tire may corn ho contact with the excavation wall (coated with MineguarcP) whereby only the direct contact site will decompose and ail other areas of the liner will remain unaltered. The flarne wiii not propagate, no matter what temperature the flame source is. Visions of an entire heading bming engulfed in flame can be put to rest. Furthermore, au~rding to the fire department, a scoop tire could onlyl genetate fire with a temperature of approximately 450 ' C. The presence of a t o m of vdculite on -d'y is solely designeci to provide an additional sacrificial char barria that will reduce the possibility of flame decomposition of MineguardllY maîerial that may corn into amtact with open flame. It is ciear that the existence of a flame retardant chetnical in the MùieguarP formulation is a necessary design requirement of this support matcrial, and will always be present. Yet, the utilizaîion of a mrfk+bonded vermiculite Iayer was included in the original recommendations by MIROC to provide &tid flame-mistance to the liner- The vdculite, however, "does nat supersede the flame retadhg effcct of the chemicai additive nor does it benefit tht strength properties of the liner in any waf' [Archibald,
213 INCO Mines Research hps ilwtsbtptd ways to opcimize the original Mineguardrrr application procedure by ahplifling the spmying prmss. This simplifiuûïon involves elirnination of the second hyer of Mùieguzvdrir in a two-pass d g pmccss, which is utilized for application of a surfêceenîmhed vermiculite materiai. This revision is based on the results of a flammability testing program conducted at Queen's University which shows that the fire retarding chernical additive contained within MincguardTY (Anti-BlaztdMD) is sufficient for safe product use underground. In same high-risk fire or heat areas, it may be prudent to use the addina1 vermidite to reduce the poss~'biiity of buniingldecomposition of the liner (e.g. adjacent to a welding bench in an underground garage)- In December 19%, an incident at NO'S Crean Hill Mine raiseci the question of MineguardP and its combusb'bility In the previous month (November 1996) Mincguard trad been sprayed in the 3800 Level garage at Crean Hiil Mm, as a repaccment for shorcrere. As a result of the application, a small arnount of overspray produced a thin mathg of MineguardTM on a mechanics siep stool and in an area on the garage floot. During weldiig repairs on a scissors lift tmck in the garage, hot metal fell to the step-stod and to the floor of the garage. When the hot meral came into contad with MkgumP, a mal1 fh stprtcd Md was quickly extïnguished by the woikas FoUowing an underground investïgath, it wu determineci that the over-spraysd mataial on the flm a d stml wu costed with grease and oil residue. The lubrication rcsidw was the Uùtiator and Jus&ining produd in the d l fk, while the Mineguar4"' itselfdid not contribute to the combustion.
214 Investigation of the Crean Hi11 fk was carried out, both underground and on surface, by local mine site and Mines Research personnel. An acetylene torch was used to ignite the floor and mechanic step stool wkre Mineguardm overspray was present. In both instances, when the torc h was removed, the flame would self-extinguish. Figure 82 shows the acetylene torch on the MineguardTM overspray on the flmr of the garage and Figure 83 shows the irnmediate self-extinguishing of the flame as soon as the flame source was removed. Figure 82. Acetylene torch on garage floor Figure 83. Self-extinguished fire (instant) Likewise, Figure 84 shows the torch source on the ovefsprayed MUieguardTM on the mechanics step stooi. Once the flame source was removed, the Batne immediately selfextinguished, Figure 85. Figure 84. Acetylene torch on step stwi Figure 85. Self-exthguished fire (instant)
215 Figure 86. Torch on ore & MineguardTM Figure 87. Self-extinguished fire (instant) Tests conducted on surface showed the same results as the underground tests, whereby the MineguardTM matenal did not support combustion. In fact, the MineguardTM coating that was on a sampte of ore demonstrated discolouration and perforation when exposed to the intense temperature and flame fmm the acetylene torch, Figure 86. As soon as the flame source was removed, the flame would sekxtinguish immediately, Figure 87. The ovenll conclusion to the investigation at Crean Hill Mine was that Mineguard- torch would self-extinguish instantly with the removal of the Oame. when ignited with an acetylene INCO Mines Research initiated further testing of Minegud-'s combustibility and resulting off-gases with ORTECH Corporation. Samples of typical combustible materiais, in addition to a variety of Mineguardm sarnpies, were sent for testing at ORTECH'S lab faciiities in Sheridan Park. Both noncellular and f d versions of MineguardTM dong with a sample of a scoop uam nibber tire, were tested for a cornparison of the off-gases produceci during combustion- Three-inch square specimens were conditioned to equilibrium at 50% RH and 23 C and exposed to two modes of combustion (non-flaming and flaming). The non-flarning mode involves the exposure of the specimen to a radiant heat flux of 2.5 w/cm2 The flaming mode augmentai the radiant kat with an array of flamelets dong the bottom of the specimen. ORTECH used the standard Bombardier SMP 800-C testing procedure for this off-gas testing. Off-gas test results are shown in the foflowing Tables 26,27 and 28.
216 Table 26. Non-cellular MincguarP combustion resuits [ORTECH, MinegmmP on Ore Bbck (apprcm 21mm total thiclrsca) Carbon Momxide (CO ppn) At 1-5 minutes At 4.0 minutes At maximum1 Carbon Dioxide (Ca ppm) at 1.5 minutes at 4.0 minutes at -rnum2 Nitrogen Oxîdes (as Na ppm) Sulphur Dioxide (Sa ppm) Hydrogen Chloride (HCI ppm) Hydrogen Fluoride (HF ppm) Hydrogen ppm) Hydrogen Cyanide (HCN ppm) Original Weight (g) Final Weight (g) Weight Los (g) Weight Loss CO/o) Time to Ignition (s) Burning Duration (s) Did not ignite - Table 26 sumrnarizes the results provided by ORTECH for cumbustion tests on the non- cellular Mineguardm ample sprayed on INCO ore, as a typical example of underground use. ' Includes approximately 160 ppm CO gerierated by test flame. Includes approximately 7700 ppm Ca generated by test flame.
217 Table 27. Cellular (foamed) MineguarP combustion results [ORTECH, Minegu- on Che Bbtlr (appror. 2lmm tow îhithas) Carbon Monoxide (CO ppm) At 1.5 minutes at 4.0 minutes at maximum' Carbon Diorride (Ca ppm) at 1.5 minutes at 4.0 minutes at maximum4 Nitmgen Oxides (as Na ppm) SuIphur Dioxide ( Sa ppm) Hydrogen ppm) Hydrogen Fiuoride (RF ppm) Hydrogen Bromide (HBr ppm) Hydrogen Cyanide (HCN ppm) Originai Weight (g) Finai Weight (g) Weight Los (g) Weight Los f??) Tme to Ignition (s) 1 2 Burning Duration (s) 445 N01-g Mode Did not ignite - Table 27 summarizes the combustion testing on the cellular, foamed MneguarP product. The MineguardN sample was sprayed ont0 a specimen of INCO on. On a few occasions during underground trials at NO, a foamy liner was ueated - this occurred when MineguardTM was sprayed ont0 very wet rock conditions. in al1 cases, the foarning occurred in localized areas and did not inhibit the basic support paformance of the liner. Includes approximatdy 160 ppm CO generated by test Barne. 4 Includes appmximately 7700 pprn Ca generated by test fime.
218 Table 28. Scooptram rubber tue combustion results [ORTECH, 199q ScoopTm Tire (appm~l5mm tataï thielrwa) Carbon Monorcide (CO ppm) at 1.5 minutes at 4.0 minutes at maximums Grbon Dioxïde (Ca pprn) at 1.5 minutes at 4.0 minutes at maximum6 N~tmgen Oxides (as Na ppm) Sulphur Dioxide ( Sa ppm) Hydrogen Chloride (HCI ppm) Hydrogen Fluoride (HF ppm) Hydrogen Bromide (HBr ppm) Hydrogen Cyanide (HCN ppm) Original Weight (g) Final Weight (g) Weight L ms (g) Weight Loss (%) Tme to Ignition (s) Burning Duration (s) Elrmhg Mode Nom-Flubing Mode Did not ignite O Table 28 sumrnarizes resuhs plovided by ORTECH for cornbusiion tests on the niwa tire of an underground scoop pun These values are the expected types and ratio quantities of off- gases that will be produced during a scoop tire fire underground. Includes approximately 160 pprn CO gaiaated by tes& flame- 6 Includes approximately 77ûû pprn Ca generated by test flame. 197
219 En~~~~~hisi~qthe~byOR~indiatcdthtthtBaabrrd*r~ utheypat.inmtoxicgasgavrrioa~mbpdiasmp800c)800c) SQseificrrrikr*tho t h e ~ ~ ~ ~ p e ~ i t i r e ~ a r d ~ v e l y ~ aibaidimodcd ~ o f ~ d i o x i & carbonmon~xide~ IncOmpuisonwiththeNbbs~t&~rmtstLproduad higher amaurts of hydmgen cyanide, but d y unda tk tlming mo& of canbuaioh Tb off-gases Listed in Tables 26, 27 a d 28 arc havdais to humam if Wed in high mncerrtrations, as per testhg ami rrsarch [ACGIH, lm- Tbesc 6w uc pobctd fiom the combustion of ali organic mstds used in the undaground work emhment As such, any means of preventing or ducing the risk offires w combustion is requitedited Ln the case of Muieguardnr, the h retuding additive Antibl- Rnlar the munipl non- combustible and aazptable fa use undagraad, as appn,vcd by the Ontario Ministry of Labour. Kthe MheguarMineg-ludN lina is ignited by uiother flame saira, the Iina will deoompose until the flame mce is removed. MineguanP itseifwill not sustain flame nor mbustion Furthemore, in the case of an underground fie which is in contact with Mineguard, d ers mut concentrate on snin&hing the source of the cornbuaion (since Min- d l sdf- ~ainguish when the flame source is temoved). As well, when an underground fke is in contact or close by the MineguardTM lier, it is reccjmrnended that mine rescue acws arry HCN gas testing equipment. HCN is one of the most dical and dangaais off-gases produced f?om the combustion of polyunthanq ahhough the concentratiions of oxides-of- carbon are produced in a rnuch higher ratio. The CAN-ULC-S102-M88 National Standard (Standard Method of Testing for Surfàce Buming Characteristics of Building Materials and Assemblies) Md Bombardier SMP 800C are recomrnended as the testhg procedures for any spray-on Liner prudua~, to arnirr cornpliance with fke retardant requirements. In cory:iusion, MhegwnP has ken approved by the Ontario Ministry of l.bair for use undergraund. It ir a m~bustible podurz and is not a fie hslard. Liewise, the pdyurea material b m Futmi, RockgumP, alsa amtains fire rétardhg additives to rrnda the pduct lkhecombustibk ad d e for umkgmd use.
220 6 SUPPORT TESIWG FOR MATERIAL PROPEKITES From eady test wack st INCO, 8 pmdktd amep of the suppat mchnism - O was dewloped m ley et ai., Indeed, it is klievd that - has 8 Wkd support fundion quite unique h esditional concreie, atcd d shotpac arches-?he ber application, whereby polyurahant liquid is ejected ont0 the rock SUmce at a high velocity, has been viewed as the key to the suppon: the high velocity application of the chernicol effediveiy mats the rocbnur sutface, and within the one-minute set~p tirne, the entire surfàce area is bondeci together with a high adhesive strength, ideally, the Liner is appiieâ ont0 newly developed headings, befon the sdkr fissures a d joints have begun to dilaie and exceed the gapping capabilities of the material. The liner retains al1 blocks together which, in tum, re(ain increasingiy larger pieces of the rock mas. This concept, which is somewhat analogous to a jig-saw puzzle, hyposhesizes that the entire rock mass becornes selgsuppor&ing, where small key blocks and wedges am p~nted bm slipping and dilating because ofthe high-tensile stmgth component ofthe Illia mataid. This theoretical support mechanism concept, for retahing and holding the rock mass together, allows the rock mass to support itself as is within the theory propsed by McCreath and Kaiser , Figure 88. The suggested simplified mode1 of ground-support intetadion is depicted in Figure 88. Refemng to this schematic, there are three main finctions ofthe ground support system:
221 ( 1) to main and hold a bmken rockmass together, and (2) to reinforce the rockmass to "... help the rockmass to support itself... " [Hoek and Brown, and (3) to strengthen the rocbs and to control bulking. The installation of stiff tendon support, such as min-grouted rebar, helps to duce buking, dilation and wall convergence. This is particularly applicable in high-stresseci ground conditions. Rock) Figure 88. Primary functions of support systems wreath & Kaiser, In applying this Figure 88 model, however, the question must be asked, what is the contribution of a thin liner? Certainly thin spray-on polyurethane membranes fit and adhere well to the contour of the excavation and provide a retaining function. MineguardTM liners, dthough having an excellent tensile suength and adhesive suength within minutes of application, can also provide a substantial ultimate ductility. Furthemore, the liners have the added benefit of serving as corrosion protection for the retaining and holding elements. Ultimately, what is the importance of the interaction of the liners with the retaining and holding elements in the context of eliminating either one or both? Can the holding elements (bolts) be removed and their function replaced by a thin liner? Can replacement of retailing screen with a thin liner perform the same function as the retaining element?
222 in an attempt to answer some of these questions an innovative laboratory testhg program was established to supplement the empirical knowledge gained through underground trials. The first series of tests were aimed at analyzhg the importance of joint infilling versus a continuous membrane coating, for achieving high load-carrying capacities. Subsequently, the testing was used as a methodology for comparing the results for a variety of Liner products: shotcrete mixes, latex membranes, screen, and other polyurethandpolyurea hybrid coatings. With Minegudnt research, there was a debate as to the ~quirement of joint infilling for providing adequate support to the excavation [Mercer, if joint infilling is an part of the membrane's support effectiveness, this then raises the concern for achieving infilling from a remotely-opented machine. The application and manufacturing experts of Mineguardm had intoned the absolute importance of ensunng al1 cracks are filled in, with the nozzle directed at 90" to the joint aperture. This is achieved with a manual application whereby a quick fmt coat (0.5 mm to 1 mm thickness) visuaily enhances the location of the rock suuchue, Figure 89. A second pas, with a dedicated effort at joint infilling, results in a complete membrane coverage, Figure 90. Figure 89. Identification of rock structure Figure 90. Weil-coated rock surface
223 Of course, the identifidon and infilhg of rock stncture d be a challenge for tde operaîed and autod spray cquipment Som ideas fa joi pnetnsig usïng remotdy controued equipment, aiitrrd rramd the use of amau near the spray (pur Thhi tkn raisal the pmbkn of kseping the camera lem clem h m ovuspmy mated, whaeby clear plastic teardes wouki be required to pmtea the crma Ium Fwhemmc, visibüity with camenis within the spray site wodd be redd duc to the ovapriy itse& cbdhg the ama. Despite intensive lightuig appmtu, the overspray cloud wwld k too thijr to penetrote the hg to gain a clear view of the rock surfàce- Overali, the joint infiilhg debate sparked tk d for fbrhr research Urto the suppat mechanism of a thin lina motaioi. Tk resesrch was quirad to define whether the intilling is a requirement for suppcxt aprcity. Two support hypotheses wcrt ventured: (1) the thin Liner acts as membrane support, where the infilling requîrernent is negligiile, yet the prevention of joint dilation is aüained through the restrainuig action of the d g - The membrane coating acts to ~bengthen joints, parti~lariy rough joints, since the normal stress would increase (clamphg the joint)- (2) the infiuing of joints is pwmount in the support of the rockmass, whaeby the joints are glued to provide additional roaanass strength. material prevents the rockmass and joints fiom puhg apart. The high tensile strengths of the liner In 19%, a testing program was discussed by INCO and the GRC to assess the support of thin liners. The testùig design used a pad of concrete patio slabs (redangular and hexagonal in shape). These slabs were butted together and used to simulate a jointed rockmass. Various d support systems were used ova top of the patio slabq for testing with a large-scak pull-teshg apparatus: (1) 6-&auge welded-wire screen, (2) Mineguardrrc, (3) MineguarcP and screen, (4) plain shotaete, (5) steel-fibre reinfocceû shotcrete, (7) mh-reinfwced shotctete, (8) Rockguar4 and (9) one latex membrane: Everbond (fiom South Atnca). Cucfentiy, FOSROC'S TeWIex is under review at INCO [Willan, but has not yet been tested with the large-de test tnm. This testing provides a badine for compsrisons.
224 In addition to the terding of d support type, therc wae a numkr of variations uscd fa the thin polyurethane membranes as well: (1) thin coafings (2 mm) and thicker applicstioir, (8 to 12 mm), and The~wasdesi~toeMkiat~thepaf~cmana~~Uisinrationswhereitisused to support jointed and/or hctured rock The method was intended to repesent, in a controlied and repeatable mamers the rocbnass deformations that can ocair annud underground excavations during progressive filure. For examplq the test Rsubr am be urd to assess the appropriate use of a thin iiner for support of pst-peak yieldimg pillars, and rock fiacturing and bulking annmd highiy stressed drifts. The test data has also been used to estimate the capacity of to resist loads hm small-scale wedge filures and to provide comparative assessments between various other area support types. The tests do not simulate rigid block movement. As descfii by Tannant , the testing was based on the use ofa 3Wmm pli plate and a large reaction he7 Figure 91. A series of corwxett block panels, hch were coated with a spray-on liner or just had the screen over-lain on the blocks, was placed under the hune in d er to load the system to generate the load-displacement data Al1 loaddefonnation data was collecteci automatically with a data acquisition sysiem (amputer and software). The largescale testing equipment mnsists of a 3O-tonne capacity reaction 6ame a hollow cylinda hydraulic ram (16dmm stroke) a load ceil a displacement transducer a pull plate
225 The readion hme hr fair legs at a If-m spacing, masurrd throughîhe centre ofthe h m~. niisspacingrrpnsa*sthcspuucbdti~pottcmdspocingurrd~inco. Foraditesfa panel is caretiilly siid and positioned over a amrrte f m or bur Onu pkbd, the hydraulicpunp~puilpediniilththdkw~ylinlahybrulicmwunillye3dendsd,to loadthepuliplate. Ibelodrddispluicn#isrwae~aaitiniaulywitbicOmpderbased data acquisition system. Wh thh syster~, the marnsd bd rc~~cy L atimned to k Figure 91. Large-scale test equipment schematic nanmmt, 1997) The benefits of using this test mdhodology are! summarizcd haatnda: good quality control and data gatherllig - without intefcupion to a mining operaiion 0 laboratory puii tests have.indy been completed for sarai and isolated panels of shotacte [Tannant 1995; Tsnwt et al and i,situ pull tests have beai complasd on shotcrrte liners ma nt 1996J
226 EaditestpanelwuoaMnicXcd~concmeb~(rrtherodanur)kaaththe~ elements. Two diffaeat typa of aiirrrtc blocks wae use& and Md shppes. The material and strength ofthe two types ofbloch wen quite diffbrmt as shown in Table 29. Table 29. Pro- ofconrr<e blocb u d for test pmdr ramant, Block Type Hexagonal SorPct Décor 682 Arvin Ave. stoneycrads Ontrrio Rainbow ancrete 2477 Maley Drive Sudbury, Ontario Dimensions The b1ocks were interlocked together to represent the jointed roclanoss, Figure 92. This figure dso shows the arrangement of the legs of the testllrg hame for the two types of test panels dong with the location of the puii-plaîe. 262 mm haregand biock (50 mm thii) Figure 92. Paüm ofamaeie bloclcs used fm the test panels Damant, 19911
227 In the centre block of each test panel, a 38-mm diameter hole was drilleci in order to connect the Dywidago bolt to the pull-plate (iocated undemeath the test panel). The puii-plate was a square plate with rounded corners and edges, The actual rectanguiar and hexagonai test panel arrangements are shown in Figures 93 and 94. Figure 93. Rectangular concrete blocks Figure 94. Hexagonal concrete blocks For al1 of the pull-tests, video and still photographie records were kept. Al1 aspects of the tests were documented in lab notes for subsequent anaiysis and correlation with the visuai data. in al1 cases except the screen testing, the physical condition of the concrete blocks (test panel) was thoroughly examined and documented- In fact, after each panel was puiled to destruction (i.e. the full extent of the hydraulic mm), an overhead cme was used to lift the test frame off the panel and to hoist the black assembly into the air. This then allowed for detailed inspection of the underside of the panel. At this point in the test procedure, calipers wee used to measure the Liner thickness dong any rips and gaps in the coating. Al1 information was docurnented and compiied for further analysis. As a base4 i ne for cornparison, the load-displacement characteristics for the Mineguardm test panels and the various aitemative liner products (shotcrete and latex) would be compmed to test panels with only screen. However, before initiating the large-scaie pull-tests with the screen, it was first prudent to review some previous pull testing with various screen types, Le. welded wire (4/6/9 gauge), expanded metal & chain-link vannant et. ai.,
228 The following Figure 95. indicates tbe pull-test resdîs for various sneen materiah. The test methodology used direct pulluig on the screen sheets, which wexe pinned to a base. O Dispiacement.(mm) Figure 95. Luad-displacements for various scceen types nannant, L99A The large-sale pull-testing design (iaying screen over interlocked blocks and pulling up the block layer) provides an additional means of estimating the load-displacement characteristics of areal support. The rectangular and hexagonal blocks were tested with #6 gauge screen. For these tests, the xreen was secureci to the concrete base to prevent the screen h m sliding under the test legs as the hydraulic ram was extended. The test frame was rotated 45degrees, with the legs located at the mid-sides of the test panel. The pull-test results are shown in Table 30. Table 30. Summary of puli-tests on blocks with #6 gauge screen [Tannant, Observations and Comment~ Rec 1 Rectangular blocks With #6 gauge mesh Blocks at centre slipped out of interlock to deform sceen. No damage to blocks & no bmken screen wires. Rec2 Rectangular blocks with #6 gauge -h Blocks in centre rotated and slipped out of interlock deforming screen only and no damage to blocks. 1 Hex2 Hex 1 I Hexagonai blocks With #6 gauge -h Hexagonal blocks With fi gmuge me& Four centre blodcs slipped out of interlock to deform screen. No damage to blocks and screen wires. Four centre blocks slipped out of interlock to deform screen. No damage to blocks and scfeen wires.
229 The load-displacement resuits for the 6-gauge screen testing are summarized in Table 3 1. with the curves plotted in Figure % (rectangular blocks) and Figure 97 (hexagonal blocks). Table Puil-test results for #6 gauge screen - peak load capacities mnant, Configuration 1 Panel 1 Peak Load (kn) 1 D~S~I.' (mm) 1 Rect angul ar -- - Hexagonal blocks Figure 96. Displacement (mm) bloc ks " O d lôû Oisplacement (mm) Figure 97. Load-displacement curves for #6 gauge screen on hexagonal blocks
230 6.1.2 MineguaridTMMTestResuits Figure 98 shows a typical setup for a pull test on Miaeguard coaied blocks and Figure 99 illustrates the examination of the underside of the tested panel. Figure 98. Large-scale testing Figure 99. Underside of test panel #8 Since one of the main test objectives was to assess the relative importance of joint infiltration, (i.e. in this case, between the block contacts) versus a continuous membrane action, a liner application methodology was developed. For the inalling test panels, the concrete blocks were taped with an industrial masking tape, but only in the centre of each bloçk, Figure 100. Figure 100. Taped surfaces of the hexagonal concrete blocks: to test the Muence of joint infiiling (between blocks) versus a membrane action
231 The gaps between the bl& cangecl h m vay tight to about 8 mm in some 1- - kger gaps were asabteci with the recîangular blo& due to impafeciioris in îhe molds. 'Lhe gap Mnability allowed the opportunity to arue~s the innuence of crack or joint openhg width on the capacity and performance ofthe Mineguarbnr liner. For three test panels, the lbhqpmp was applied in a relatively üiidc colitii>g (a-g aboui 5 to 6 mm thick) while al1 other panels had thinner coatings (averaging 2 to 5 mm thick). The Muieguardrrc and screen tes& panel had a thick &g ofthe liner. Tabk 32 shows the pull-test results for MhegwrdrY applied over #6 gauge screen, and Table 33 has the summyy of the pfain MineguarP pull-test redts. Table 32. Pull-test results for MineguarcP applied over screen [5annant, 1W7] 7 8 rectangular bloçks with #6 gauge screen rectangular blocks with #6 Wge screen 4 to 10 mm High laad capacity- Definite membrane.dion The biocks were severely fh%ud near the pull-plate by the end of the test. The liner-to-block bond Wed in many locations. 4 to 10 mm High load capacity. Sudden load dmps caused by sakn wires breakhg near support plate. Dcnnite membrane adon Blocks severely crushed near the pull-plate. The lina-bbiock bond füld.
232 Panel Table 33. Pull-test results for MineguudlY on blocks hexa%d blocks rectangular blocks rectangular blocks redangular blocks redangular blocks Unifffm cmin& compldy fmng the cracks. P ~ w a10to s M-mm into tbeblocjcoontqds that wae 2-rmn wide at the top. Ti- 1 to 1-20 mmcodw~bdpavtntioaof.bait6to71~l AAa~Imciisionpull,muiyb~wat~ and aushed. Lina&lock adhesion bata than the blocks. Ahhough blodcs were broken, the liner held pieces togetha. - Most ad<s 63lad-u~ with MùKguud. Significuit block-to-blhegud interaction Blocks crushed or aacked; obviais membrane action Mineguprd tore along thme lines. Plastic load-defonnatiori Two large load driops at displacements of 18-mm and 32-mm likely due to debondhg (m crajrs in the Mineguard were obmed). Mineguard membrane nipaircd sddenly in ont iarge crack north to muth near middle of panel at a upward displacement of %mm. Thkknes mclisurcments were taken dong rupture. The blocks were severely fiadurd near the pull plate by the end of the test. The bond between the blocks and Mineguard fiuled in many locations. Many partially filled cracks and some open contaas. Poor penetmtion of Mineguard ho cracks. Blocks separatecl relatively easily along cont;ras and simply "lifted out". No "membrane action". L i damage to the blocks. - - Al1 wide cracks coated with Minegwd. No aacks in the Mineguard until der about 100 to 120 mm displacement. Thiclaiess meamred dong ruptures. The blocks were severely âactured near the pull plate by the end of the tes. The bond betweat the blocks and Mineguard fiiled in many locations. -- Miidurr of cotnpleteiy filld coniscts d p.rt*lly filled contacts, B1ocks separated relatively easily along contaas. Little or no "membrane action''.
233 - Table 34 results fotthe tpped bbdu ud ifillbg Table 34. hlts for pull-tests on MineguardTY infïlling panels Fumant, 1991 I Panel Observations and Commetaped- not mezlsufed blocks taped rect. blocks taped hexagonal blocks not rrmmred The Ioad-displacement capacities of the different -- ~ Tape embedded in the Mkgud at rome locations - poapiad Twotestsweccpafamsd. lawithiegs batcdrmidsidgoftbeprrldt'arahlqp batednearcomarofpuul. Stoppcdl'teS&* less than 100 mm displacement because blocks below 2 legs began to rdatc. No plates on the legs. Tape embedded in the Mineguard a some locations - p0orp-l Only a few centrd bloclcs were W upwards during the t e The Mneguard d y debonded h m the taped blocks and the lack of membrane-bbck interadion greatly reduced the I d capacity. pull-tests are surnmarized in Table 35 (for thick & thin applications ofmineguarm, Table 36 (for joint infilhg tests) and Table 37 (for MineguarP and screen test panels). Table 35. Lod-displacements for various thicknesses of MineguarcP [Tannant, 199q Test Panel Configuration 1 Panel # 1 Peak Lad 1 ~ispl.' (mm) 1 rect. blocks with thick liner hexagonal blocks & thick liner 1 4 I 40.4 I 47 I 7.8 rect. Blocks with thin liner l
234 Table 36. Load-displacements for Mineguardm infding panels [Tannant, Test Panei Configuration I Panel # 1 1 Diil.' (mm) mped hexagonal blocks & Liner rectangular blocks & Liner 'Displacctmnts arc Measunxi at Pirk Load Table 37. Load-displacements for MineguardM and screen test panels Pmnant, l Test Panel Configuration panel # 1 Peak Load (kn) 1 ~is~1.l (mm) 1 rect. blocks and screen & liner Figure 101 illustrates the results of the puil-tests on MinepardTM using the hexagonal blocks. The upper load curve is for a liner thickness of 8 to 12 mm, while the lower curve is also for a thick application (7 to 10 mm) but the blocks were tapeci, to test the effect of only having joint infilling. From these results, there is a substantial reduction in the load-canying capacity of the liner when only the joints are infdled versus a continuous iiner coverage over the blocks, O Displacement (mm) Figure Lad-displacement results for MineguardTM over hexagonal blocks
235 This result of lower capgcity with joint Miihg alone, is again demonstrated with the tests of taped blocks using the rectangular test panels, Figure 102. In these tests, a peak load capacity of 15 to 20 kn is achieved with relatively litde deformation (20 mm), yet it was not recorded how thick the application of the Liner was, for cornparison with the previous tests (F~gure 102). It can be assumed thai a thick application of Minegu- was also used for this test, based on discussions with the applicator. Overall, the infiig capacity of MiwguiiCdTM is similar to that of the #6 gauge rreen tests. Certaïniy, if the liner is only applied on rock block surfaces, the load capacity would be nil; therefore, some infilhg appears to be usehl for rock support. However, it is clex that the infilling is not as important as a continuous membrane covenge.! I i 1 I 1 I 1 O m 100 IM Oisplacement (mm) Figure 102. Load-displacement curves for liner infiiling with rectangular blocks Dunng the largescale pull testing, the bloch and liner interaction were carefully examined. It was evident that the MineguardTM liner is capable of hfiitrating the cracks between the blocks (with penetration up to 10 to 20 mm) yet the adhesion between adjacent blocks did not appear to be very good. in cornparison, the continuous coating of Mineguardm over the blocks served to mobilize the inherent strength of the blocks themselves, to resist the pulling action of the pullplate. in fact, during the testing, the blocks were heard to gmd and cmsh. Post analysis showed the blocks were cmshed in the centre of the panel, with radiating cracks and fractures. This test result reinforces the support hypothesis that the membrane inc- joints, to strengthen the joints and the rockmass. the normal stress on the
236 Figure 103 illustraies the load-displacement resuits for MineguardM applied over #6 gauge screen. Although the Liner thickness is substantial(4 to 10 mm), the capacity of the combiion - of support elements is triemendous. Compared to the resuits of scren alone. the Mineadds capacity and stiffness (i.e. peak load of 6 kn at 140 mm versus peak ld fi, of 80 kn at 60 mm of displacement). Figure 103- Load-displacement results for Mineguardm and screen The peak Ioads achieved for a thinner Mineguardm liner (i.e. 2 mm) over the rectangular blocks, Figure LW, is comparable to the pedc load measured for #6 gauge screen. O Displacement (mm) Figure 104. Load-displacement curves for MineguardTM (2 mm)
237 The capacity results for thicker applications of Mineguardm a~ illusiraied in F p LOS. The liner was 4 to 10 mm thick for these panels. It is clear thaî the stiffiiess of the polyurethane is greater than that for saan, with high capacities king achieved with low defonnatons. Scrpen typicaily achieves peak capacity after 100 mm of movement or more, while the polyurethane liner requins a fifth of the deformation to reach peak capacity. O Displacement (mm) Figure 105. Load-displacement curves for thick applications of MineguardTM Another important observation hm the load-displacement testing of the MineguardTM liner is the shape of the curves. For most tests, the iiner exhibits a substantial pst-pk capacity, with almost perfectly-plastic behaviour to a deflection of 100 mm, appmximately. From a support point of view, this type of charactenstic is important where large deformations are likely to be experienced, i-e. with bulking around tunnels at depth, in piliars, etc. The elastic, perfectly- plastic behaviour also signifies an abiiity of the iiner to effectively absorb released strain energy. Again, this makes the liner amenable to use in seismicaily-active mining zones, since the energy absorbing capabilities are greater than Sgauge screen, for example. In fact, the areas under the loaddisplacement curves for #4 gauge screen and Mineparci- si mi lar e nergy absorbing capaci ties. Furthemore, Mineguard- are quite close, which indicates is recornrnended as a retaining component in deep mine environments since the 150% elongation allows the liner to handle potential rockmass bulking (due to mckbursting or stress-fncturing).
238 Sorne illustrations of the testing and the results are shown in the following figures. The obvious lower capacity hm thin iiner applications is &monsuated with the ciifference benueen Figw 106 (thick application) versus Figure 107 (thin application). Note thaî tbe thick coaring caused the entire block assemblage and her to deform into a domed bulge whiie the <hin liner snapped. Figure 106. Thick Mineguardm liner Figure 107. Thin Mineguardnr liner At high displacements, the MineguardTM liners experienced ensile rupture, Figure 108. The joint infiltration of the liner was measunble during a p st analysis of the test, Figure 109. Figure 108. Tensile rupture of the liner Figure 109, Joint infiltration of the liner Joint infiltration was incomplete, with long driplike strands of liner forming rather than a continuous bond between blocks. The rapid tirne to set-up Iikely influences the depth of penetration whereby only a srnall depth of peneûation is achieved before the liner hardens.
239 Testing with the MineguarcP and screen showed extensive load-carrying capacities. Very Little damage oaiurred until the displacements became very large (>LOO mm). The Mineguardm began to puii near the legs of the fiame, aad at higher displacements (150 mm) the wire of the screen snapped, Figuri: 110. Figure 110. MineguardTM and screen testing: screen wire snapped Figure Testing fiam and concrete base used for pull-testing of block panels photo: lay Aglawe, Samantha Espley & Dr. Dwayne Tannant] Al1 of the testing was conducted at the Willet Green Miiler Building on Laurentian University's campus under the dktion of Dr. Dwayne Tannant of the Geomechanics Research Centre, Assistance was provided from various graduate students at Laurentian University. The test frarne, Figure 11 1, was designeci and fabricated in Sudbury to be stmng enough to test very large laid capacities.
240 Overall, the test design wpr mccessfùl for assessing MineguarP as a continuous c dng versus a joint-infiilling agent. summarized hereunder. Som very usenil information WU detamined, ps MineguarP upacity is cntically dependent on the ability of the Liner to bridge across the joints or gaps in thc rochnass, to aeate a continuous membrane. A thick COBting of MineguarP is better aôk to build a "bridge" over wide gaps (>2-mm). Euly tests by MIROC/Queen's indicste the possibility to introduce rom wita during spraying to create a foamy material, to Mer bridge across large gaps wercer, MineguarP had a lod-carrying capacity of 15 kn for a liner thickness of 2 to 4 mm MineguarP was able to achieve high load-carry capacities of 40 kn (at 60 mm deflection) with thickneses of 4 to 10 mm, as compared to peak loods of 0.6 to 1.5 W (at 140 mm displacement) for #d gauge screen Mineguardm over scran achïeved very high capacities, in the order of 80 to 100 kn at a displacement of60 mm, for fairly thick liner watings (8 to 12 mm). Based on these results, Mineguarbnand-screen wouid be an effective replacement for shotcrete, as a secondary support element in diffiailt mining areas (Le. in high stress environments such as at depth, or in the mining sills, etc.). This assumes the liner un Mthstand 0thoperational impacts, such as fly-rock bombardment etc. peak loads were achieved over relative1 y low displacement values for MineguarP, indicating the high stiffhess and a definite benefit for using MineguardTY as soon as possible in the support cycle to aïd the rocbnass in maintainhg inherent strength the hexagonal and rectangulu block types (with different thicbieures anâ strengths) resulted in different peak loads and different adhesive strengths with the MineguarcP
241 Puli-testing of shotcrete panels was requested by INCO Mines Research to the GRC. Shotcrete tests were required in order to male cornparisons of the 14-displacement characteristics of Mineguardmf liner combinations with the shotcrete combinations (Le. with and without steel rein forcement of screen and steel-fibres)- The test panels were assembled by INCO's Research personnel and delivered to Shotcrete-Plus for the application of shotcrete, Figure 112. INCO siandard shotcrete mix was used for four panels and the Stobie fibre muc was also sprayed for two panels- figure Shotcrete spraying ont0 test panel for large-sale pull-tests For two panels, #6-gauge screen was overlain on the blocks prior to shotcreting. For these panels, the screen was slightly raiseci hm the concrete blocks to allow for embedment of the screen in the shotcrete coating. AU panels were sprayed to a thickness of approximately k m, as gauged with steel nails protniding hm between the hexagonal blocks. Six panels were sprayed: two plain, two steel-fibre, and two with screen. Only four panels were actual ly tested since the two plain shotcrete panels were damaged during transpomtion to the Willet Green Miller Centre due to the brittle nature of shotcrete.
242 Once delivered to the test site, the panels were doused with water and wrapped in plastic to aiiow for hydrated curing over a 28day pend After curing, tbe panels were tested with the sarne methodology as the large-de pull-tests on MiaeguarcTM. The results of tbe shotc~te pull-testhg are surnmarized in Table 38 (Le. Panels X 1 and 2: rnesh reinforced shotcrete; Panels #3 and 4: steel fibre reinforceci shotcrete)- Table 38. Pull-tes t results for shotcrete panels rïannant, TFf=F Panel # Thickness (mm) Peak Load Sudden drops in load due to wide The tests indicate that the mesh-reinforceci shotcrete was iess effective at preventing cracking in the shotcrete with smd displacements (i.e. <50 mm). However, with larger &formations, the tensile strength of the screen was mobilized and the wires and shotcrete combineci were able to carry very high loads. The mesh-reinforced shotcrete panels were stronger than the steel-fibre panels, Figure 113. Figure Load-displacement curves for reinforced shotcrete [Tannant, 19971
243 The testing of a wsh-reinforced shotcrete panel is shown in Figure L 14 (complete extension) and Figure 1 15 (after puii test complete - examiniag un&rside of panet). Figure Pull-test of meshed shotcrete Figure Back of mesh shotcrete panel The load-displacements for the h t 25-mm of deflection (hm Figure 1 L3) showed interesthg results, Figure 116. Up to this point, aii shotcrete panels exhibited exdy the same elastic response and achieved approximately 25 kn of load. As soon as the f3st crack was generared for the mesh-shotcrete panels, the load dropped by about one-third. However. with added displacements, the Ioad begm to rapidly climb again. The peak load was reached at 60 to 65 mm displacement, with a gmdual drop with added &formations. At 150 mm of displacement, the rnesh-shotcrete panels still c-ed 40 W of capacity. Figure Early load history for shotcrete panels [Tannant, 19971
244 According to the Figure 116, the steel-fibre shotcrete showed a very eariy peak load response (at 5-mm of displacement). No additional ld capacity was achieved, with a gradua1 decrease bm about 25 and 40 kn at peak (for 50 to 60 mm thickness) to 420 kn at 40 mm of displacement. At 75 to 85 mm of displacement, the cracks in the panels were quite pronound and some large load drops occurred beyond this loading point. Figure 117 iilustrates the pulitest on the fkt steel-fibre shotcrete panel before pulling, and Figure 118, after puhg. Figure 117. Puil-tests on fibre shotcrete Figure 118. Cracked fibre shotcrete panel From al1 the results of the pull-testing, Figure 119, can be used to compare capacities of MineguardTM (4 mm) with mesh-reinforced shotcrete (60 mm) and steel-fibre reinforceci shotcrete (60 mm). Figure 119. " O Dispbcement (mm) L,oad-displacement cwes for MineguardTM and shotcrete marinant, 19973
245 Based on loaddisplacement rrailtr fw M qpanp and shdtary the fduowing co~lclusions can be made: 1. - the shot~etc panels displayed a much stiffer mpme to loading 2. -thepeakkdap.àtyofmineguard"warsimil~tothatof~tibrcrinfwad shotcrete and was less than mesh-reinforcd shotctete 3. - Minegriardn (2 to 4 mm) and steel-fibre shotaete (60 mm) carry ova 25 kn of I d over a displaument of 100 mm 4. - the loaddisplacement nsponse of MineguarP (8 mm) anci steel-fibre diotcrrte (60 mm) are very similar 5. - aü panels gave prr-airsory indications of pending abrupt ~Ufeslruptures. In fi4 au sprayon products had dramatic load-drops and obvious damage during the urrrrred displacement loading. The Geomechanics Research Centre acquired a srnall quantity of Everbond latex rock support product fiom South Mca After approachhg INCO, it was agreed that a large-sde pull-test wodd be conducted on the latex produq using the hexagonal bl& as the simuiated roclows base. This work was conducted after MheguardTM testing was complete. From the rqmt to INCO naman, 1997 the hexagonal blocks were coried with the latex using a paint-bnish application Tw were given to the blocks, with a 30 minute sdup period between mats. The thickness oftk liner at the time of application was esthated to be 4 mm Mer a wing time of6 days, the test panel wu positioned on the testing platfi Tk coafing was f d to still be tadcy to the toudr The panel was pulled to the fiiu extdn of the mm, and the liner failed by tende rupture in numaouo 10CatjOIISOCatjOIIS Meamremen& of the Mark1 thickness revealed an average mathg thickness of 1.6 to 1.8 mm, with a muomum of 2.5 mm
246 Based on viscosity propenies, it was estimaterl that the ha1 dried thicbiess of the coying in a one-pas opedon in an underground mine would not k ly be more than 1-mm. It would difficult to apply a one-pass coating any thicker ihan 2 mm in the ovemead areas of the mine. The pull-tests are iliustrated in the following Figure 120 (pawl ready for testing) and Figure 121 (latex panel at the end of the test). Figure 120. Latex panel for testing Figure 121. Latex panel failed blocks The load-displacement cwe for the latex pull-test is show in the following Figure Oisplacernent (mm) Figure 122. Load-displacement curve for latex (Mark 1, Everbond) [Tannant, f 9971 Latex can be compareci to Mineguard-, with norrnalization to liner thickness, Figure 123.
247 O I i I I 1 I l O ; Oisplacement (mm) Figure 123. Load-displacement curves for thin MineguardTM and latex. From these results. it follows that the latex product has approxirnateiy onequarter of the load capacity of Mineguardm. Large-=ale pull-tests were conducted on 10 test panels with Rockguard-1 polyurethane/polyurea hybnd coating, with the analysis and testing completed by the Geomechanics Research Centre [Tannant, for INCO Limited. These tests were requested by INCO's Mines R-h Department in order to compare the resuits with the previous testing of shotcrete, latex and MineguardTM. The test methodology was sirnilar to the previous load-displacement analyses. using the same large testing fnme and the data collection system. The Rockguard-1 coating was the first generation product pduced by Futura Coatings in St. Louis, USA. This was a much stiffer pmduct, and the formulation has since been altered to produce a more elastic behaviour (elongation of ioooio versus the Rockguard-1 elongation of 50%). in cornparison, MineguardTM has elongation properties on the order of 150%.
248 Table 39. Pull-test rrailts for Rockguard on hcxagonai bloduî puuunt, ûbmdons ancl Commenîs I I ~rittle-hilm dong aacks I Liner had gaps at the block contacts r Problem with displacements at start of test No comments One crack fod suddenly across panel The peak loads were higher for the giued panels, as cornparrd to tests #5 to #IO. The haease in peak load (for the sarne thickness of liner) was between 30 and W? higher than the raglued specimens. This indicates that the mkmass contributes additional load bearing Capacay to create a system that is able to cury hi* loads t h those predided in the Mescale tests. The peak Io& were achieved within 60 mm of displacement. The glued panels achieved ptslr Ioads at Iowa deformations, in the orda of 7 to 10 mm. As compared to Mi-, the measured pepk losds wae lowawith Rockguard at 15 to 22 kn. Hbwever, when the lodp are normalized to the liner thicknesses, it is f d that the two pl- pduds have v q sirnilar load carrying capaciges, and veq similar stif16iessesesses
249 The load -displacernent cuves for the Rockguard panles #5 to 10 are shown in Figure Test Panel O O Displacement (mm) Figure 124. Load-displacernent curves for Rockguard panels (#5 to #IO) [Tannant, 1 Ovemil, the conclusions of the testing are as follows: 1. - a Rockguard-1 iiner of 4 to 6 mm thickness has a capacity of 15 to 22 kn (without gluing between the concrete blocks). This is equivalent to #9 gauge screen or to 2 to 4 mm of MineguardTM 2. - the glued blocks increased the capacity for the Rockguard-1 liner of 4 to 5-mm thickness, by about 3m to 20 to 29 kn The most important ciifference between Rockguani-I and MineguardTM is its brittieness: 3. - the Rockguard-1 liner could sustain 50 to 60-mm of displacement before tensile rupture occurred. There was Little pst-peak strength foliowing rupture of the iiner. The liner demonstrates an elastic brittle-fdure response.
250 In 1998, sorne tensile straigth tests wae perfi b] 1 the GRC, wih a newly dcveloped testing device. The teras fobw the ASTM-D638 Mndsrd spacindons for Ule straigih tests- INCO contraded srne tensile strength testing of the Rockguard-1 podua to the GRC [Tannant, A thin layer of Rdcguard-1 was applied to concrete blocks for the largescale pli- testing purposes. Mer the tests were oonduaed, some of the 6om the concrete panels and ait into dog bcme shapes for tende testing. mataial was removeû The ASTM-D638 standard spscifications were fouowed for the testins with the pre-cut specimens of Rockgmrd-1 material. A total of six specmiens wwe tested in a loading firame, at a loading rate of N/s. The results are summarized in Table 40. Table 40. Tensile tests on Rockguard-1 [Tannant, 19981
251 Various testing amuigemorits have ben US4d ovet the iast fw years to measure the -ive strength of spray-on liners. Using h test dences, somc vaiues have been estimated for MineguarP, Rodtguerd-1 ud latac poducts. Testing by U*n Plastics Inc. suggests that the mgth of the Iuia is directly propottionai to the liner thickness [Carey, 19%]. Therefre, there is no upside Iimit fw load capacity aside fiom a practical, ecommic one. However, this limit wili be detennined, by the sûmgth of the MineguardTM itsek but by the strerigth ofthe adhesive bond between the rock and the Liner- When a liner acts as a fetaining system, the maximum usefiil thickness therefore depends on the weight of the rock to be "suspended" in the liner. Two different adhesion testing methods were used to gather an undemtandiing of the strength magnitude and the influencing factors. IZXT #I: Adhesion tests were performed on the MineguarP materiai, with applidon on concrete blocks (with strength ofapprorrimately 20 MPa). These tests were contracted by INCO to G.L. Stone Consulting Ltd. in Mississauga, Ontario [Stone, 1997). The leaover blocks ficm the large-scale pull-tests were salvaged and sent for the external testing. For each test, a &Uy was afbxed to the MineguardrY liner. Araind the pairneter of each doiiy, the ha wu ait leaving a remaining chle of The liner was then pulled hm the ccmmk slab using a spring-ioaded instniment with a calibrateci d e indicating the pressure applied. This procedure is a stight modification of ASTM D Sandùig, grinding, and phcularly cutting has the patentid to di& the adhesion of the coaîhg with microcrackhg in some films.
252 In the opinion of the testing Company, micocfacking has not occurred in this coatiag, as it was found to be very elastic. However, the cutting operation may have disnirbed the concrete substrate and this was stated as tbe cause of some lower adhesion vdues. In total, 24 tests were completed of which 22 were found to be valid The adhesive strength rmged h m 0.35 MPa to 1.85 MPa For each test, the representative percentage of faiiure of concrete versus the percentage of failure at the concriete to liner bond was stated Four tests wexe found to be representative of 1Wo adhesive failure, at the concrete to liner bond. The strength value for these tests averaged at 0.82 ma. TEST #2: Another set of adhesion tests were conducted on MineguardTM coating concrete blocks W. Tannant, for NO. Co~g was used to bore into the concrete blocks until the liner was encountered. At this point, the core was attached to a pulling fiame and the loads were recorded as the core was pded h m the liner. The testing apparatus is shown in the following Figure Figure 125. Adhesion testing arrangement [Tannant, 19971
253 Atdnlof22tr~1waecom~irirui(ll i n t k ~ ~ b b d c 11 ~ hthe u d hexagonal blocks). The redis for the dhaion tes&ing with the were 0.19 MPa W e the hexagonal blodc< yieldtd an dhcsive Conaac bbdo of0.38 MPa For these tests, a range of diffkent size drill bits (cores) wen tested to derennine the dvity of the resuhs to adhesive surfàce uea F m the mu& it appam as ifthe 35 and Wmm core diameters give the mmt diable and amsistent rtsuhs. ïew#3: A third saks ofdhcsai tests wae panwmd by the GRC using a modifieci tcsting procedure [Tannant, 1998; suhrhd, at thc request of INCO, Mhes Reserrcb This project was aimai at dasmining the influence of the quality of a spray* liner application on the overail -ive strength. Such fvxor~ as: humidity, dust, dit, oii midue, and sudb darnpness were fkctors thaî iïkely influence a qunlity -ive strerigh Two underground sites at XNCO were useâ to colle!ct the bu: McCreedy East 153 OB (as an extaision of the stand-alone triai of Mineguardn? and the 175 OB, Rseardi Mine, with testing of various applications of Mineguarbn' and Rockguard. ïhis work was conduded by Ken Sutheriand at Lauredan University, as partial rquirements for an undergraduate thesis in Mining Engineering. Review and direction was provided by Dr.D. Tannant. To test adhesion accurately, the prrvious test arrangement was gr- d i e 4 in orda to accommodate both lab and undagmrnd test sites. In the new test anangement, steel doiiies (which are punch-pressed fbm perfiorated sted sheets) anz p&ced ont0 a hih (not yet cured) coaîing of polyurpthane lier Md the dolly is re-coated imrnediately. This embeds the dolly in the Liner. A coring drül bit is used to over-cote the dolly, and thai a pulling device is ujtd to siowiy pull the douy away h m îhe oubsfraîe. While puuing an the douy, the irorce a d displacements are recordeh This test rnethodolgy is usefiil fw lsboratory environments as well as the undergromd hesdings. The underground testing arrangement is shown in Figurc 126, with a schematic of the douy, Figure 127.
254 Figure 126. Underground test arrangement for adhesion tests [Sutherland, Figure 127. Schematic of a steel dolly used to test adhesion [Sutherland, Application of Mineguardm at the 175 OB sump area occurred during the fa11 of This area, at the time of the application, was wet, with some clear areas that were dnpping with ground water. The adhesion of the Liner in approximately 75% of the area is good, visually, with no signs of draping or faliing sheets of material. Srnail patches of MineguardW did peel from the rock surface, as water continued to accumulate khind sections of the rock walls and back. Field testing of the adhesive strength of the Mineguardm liner at the McCreedy East Mine, 153 OB, indicated poor adhesion dong surfaces that were still wet when the application twk place. From the study, the substrate properties ont0 which the iiner is sprayed and the cleanliness of the application surface are the two key factors dictating the strength of the adhesion in the field.
255 A summary of the dhcrion are prwided in the toilowhg T.bk 41. Table 41. Summuy of MineguarcP adhesive s~rength tests onmnoussubstrzde~s[suthaland, TestLocati011 Lab 1-37 Comments 2" Dia. Disc, Brsccie Rock - ~ McCreedy 153 OB " Dia DIS, B& Rock McCreedy 153 OB " Dia Dise, Br& Rock 175 OB "DiaDIsc,CoriaettBIock OB " Dia Disc, Cancrete BIock 1 The application of MineguanP at Copper CWNorth Mine occwreed in a relatively we$ and humid environment, in the fall of Ahhough there are no visual signs of poor adhesion, it is physically possible to ped pieces of the liner fkom the 4. Iî is unclear though, whdha the poor adhesion is a rwlt of the wet conditions, the dew point issue, or to impropa cleaning. Testing and experience Udicates that the -ive stnmgth ofthe polyurethanes is compromisexi when the materiai is appüed in excessively wet areas. The tedng, thgh iimited at thh time, indicates that the more fiable and d e r materials will allow the sprayon liner to ped hm the excavation. Although the aifiinl adhaion between the liner and the materiai is excellent, the weak rock itself is permitted to fail. This is a m m for extensive amas with very aiable material, such as a massive dphide ore mm. It is the opinion ofthe auîhor that a spray-on liner couid diil be used in massive sulphide ore stringer yas, whem thae is "bridginf of the iiner support aaoss the siringa. with good adhesion on the adjacent ho* roda. Ushg GRC's test procedures, dditionsl dhesive strength tests were pafd by the GRC fm MineguarP and for RoCkgUprdCY, as well as the Evabond and TekFlex ptodllcts.
256 63.2 Everbond Latex Adhesive Core testing was conducted by the GRC under contract to inco to detennine the adhesive strength of the Mark1 Everbond latex maienal. The resutts are plotted in Figure O 5 to 15 Dispiacement (mm) Figure 128. Adhesive strength results for latex materiai vannant, The average Everbond adhesion was 0.2 MPa for concrete substrates whde MinegdTM averaged an adhesive suength of 0.38 MPa for the same materiai. Ten adhesive tests were perfonned to aises the strength and to compare with the Mineguardm pmduct. Rockguard was sprayed ont0 concrete blocks and were tested in the same mamer as previously described. The test results are shown in Figm 129 and summarized in Table 42. Figure 129. Load-displacement curves for Rockguard adhesion tests uannant, 1998)
257 Table 42. Adhesion test results for Rockgtwd [T~ll~nt, The adhesive strengths of MincguardrY and on limited data) appear to be similar for the same substrates- Lower adhesive strengths were found with weaker concrete materials,whiie higher adhesions were measured with stronger materials (We gide). The large-scale pull-tests provide a gend comparison between sprayon prududs and screen Some elements of the field application were captured with this testing mdhoddogy, although some aspects will not be well represented by the results. Additional field trials are recommended, using this information as a basis for initial design. The membrane adon appears to be compromised where poor adhesion ktween the blocks and the costing and where the costing cannot adequatdy '%ridge'* gaps or joints. Therefore, fbture pull-tests should attempt to assess the mating performance using adhesion tests and some method to test the effkdveness of the "bridging". The pull-tests effectively capture both influences in one test when blocks are used to build the panels. However* using pull tests to quanrify the individual effects of either adhesion or bridging is impossible. Nevertheiess, the puil tests give a good o d measure of the effediveness of the coating.
258 7 SUPPOm CONSIDERATIONS In the absence of Cxpenence, the design of new support systems for umhgmd hprdrodc mines e d s a kngthy enghœrhg poaar. The fdowing dioaia<ion provides a &ew some cori~idartiotrr fm Urapatiai within support designs fm mdecpud (umla emphasis ofthis design disaurion is with regard to spray- of The liner systems and, as a them is a critical feview of the support mschuiism and fulure modes. The cppacity of poiyurdhone finers is detaüed, with an exomuiotion.. of unpiricd and dyticai design mcthods. Using th compilation of data, a summry of the fscommendatiow ud design guidclinej are offi fbr reference. The objective of a gnxind support system is to essist the rocbnass in çupporting itself. In fkct, it is very difficult for support to be able to hold up large volumes of dead weight loading once the rockrnass has loosened [Hoek & Brown, 1980k in blocky ground, thin pl- I' iners ads as a cohuous, impermeable lining to pevent the rockmass h m mvelling and loosening thereby enabling the mclanass to maintain its inherent strength. This is the basis of key-block theory that states: +llporentidly are stqprtd lhen th rerrrmrrrmnrjer of* r0cknm.w will reltl~an stable chre to an imhiliiy to maie. In conventional support rnethods, the large key-blocks are held in place with the use of rock bolts, or other tendon supports, while the srnall pieces of the rockmass are held in place with screen Surface confinement, cither in-kind replacement or in addition to scmq cui be gained with other retaining elements such as thin spray-on membranes. For most INCO Ontario Division mines, the recainuig element is required since the joint spacing is on h order of 0.3 m, and less than the bolt spacing of 1.2 m, typically. By contrast, extremely massive rodonur uas do not require the additid d support, unless heovily influenced by stresses that are geater than the rackmass
259 From many experirnents and triais, it has ken concluded that the retaining element plays a critical role in the stability of a fockmass. The retaïnïng element, in fxt, does not need considerable strength. It just aeeds the abitity to limit the kinematic movement of small wedges, thereby abmptly preventing any unravelling of the rakmass. This mechanism ensures that the fabric of the rockmass is maintained, to dlow for the creation of a rock beam or a rock arch to stabi 1 ize the roc krnass around the excavation. In a further effort to aid the rockmass in king self-supporting, consideration should be given to the timeliness of the support installation. In fact, for most underground situations in low to moderate stress levels, ground support should be instaüed as quickly as possible within newly blasted headings. Fast support installation, as provided by thin spray-on linen, limits the amount of nxikrnass loosening and aids in preventing large volumes of dead-weight load from developing. In compaiison to screen, thin spray-on Liners have the benefit of king in direct contact with the rock surface. As such, the liners have an improved ability over screen in preventing rochass displacements in the skin of the excavation. 72 ThinLjnerSuppœtMecbnh In order to design a support system to withstand the applied loading conditions in a heading, it is first necessacy to understand the support mechanisms. Bolts can be assumed to suppon the rockmas by pinning the imse wedges around an excavation into the solid rockmass. Each bolt is drilled through a wedge with the bolt anchor secunxi within solid ground. Each bolt is assumed to support a given area of the exposed excavation back or wail, figure Figure Support of a wedge with bolts
260 Inanunsuppatedarea, aweâgewiil fàiiwhentheco&rioaand~arc kaiongpersisterrt joint daces. However, 8 d unauit ofjoii d l provide aiaigh bdzurying cap.citytohddupaiargcwaigc. h~8~dhckhidge(iiuaiodt~)ai8 discontinuow joint airarc can provide the sme support crpacify as a crbk bolt w c h s & Kaiser, 19983; this support is due to the mcknuss tende load bearing capacitycapacity An aumple of the &ed of the rock bridge load capacity is provided hereunder: Assuming that the ullconfined ampmssive strength of the rdamm, a., is 150 MPa, thai the tende s~rength is estirnad as 15 to 30 MPa (since o = 10 to 20% of a 3. For a d l rock bridge, 0.1 m square, the bd cspacity due to the rodamss terisile sbength can k dculated. Rock Bridge Load Capady: C ib = area fi Where: arear=0.01 m2 and at=1sto30mpa :. C~=(O.01)(15 to30) = 0.15to0.30MN or 150to3ûûIrN :. a 10 cm by 10 cm r d bridge will support a wedge weight of kn 0 Assuming: y = 27 kn/rn3 (for rock unit weight) Assign: s = wedge edge length (for qual sided wedge) 0 Since: Wedge Load = ( Wedge Volume Unit Weight ) 1 Wedge Pairneter Then: ~e=[(213)-(d)(&)-~] I(3s) :. s = 2.3 m This cdcuiation indicates that 10 an square rock bridge, dong a joint fhturc, has the teiisile load cprrying capacity to support a wedge weight of 150 to 300 W. This equrtes to a wedge with edge lengths of2.3 rn This rock bridge provides the equident support ofa cable bolt
261 Ofcuurse, as a rc8ult of niinng dvity, th excavotjon arbitity caild b&om aitially ihatd. Due to the infiuena of stress dwge (relaxatii) and gravity, the thee bd bmng cspocity may becorne exceeded thereby dting in the breaking of rock bridges. In îhis sini9tion, the need for other reinfoccement support, fiom rock bdts or otha tendons, waild be required for maintairing the excavation stability. The support h m the rrtpining dement waild not be sufficient to reinforce and hold large volumes of fàüed rodq f& either fiorn wdges created with newly-persistent joint fatuns a due to stress hctwhg In a stand-alone application, the sprayon liner provides rock stability in a d E i manner than bolts. The Liner provides support dong the joint pec*l of the wedgg Figure 13 1, whereby the load capaciîy can be dehed as: ficep unit lenglh. Wedge Wedge Perimeter Liner Figure Support of a wedge with a sprayon lina
262 73 Failure Modes Iinar The four potential mechanisnu offgilcut are defined as: 1. Adhesive Failure 2. TensileFailwe 3. Direct Shear Failure 4. Diagonal Tensile Failure 1. ADHETIVE FnURE: LQSS of adhes'in can ocair either by debonâiig (of îhe liner and the substraîe material) or by delamination (of the substrate itsee whercby weak and friable rock becornes detacheci fkom the surround'ïg rockmas). Liner adhesion is critical for distributing and transfeèrring applied loads across the rockmass sudice and withui the liner. Furthennorem, adhesion prevents the imsening of the rock blocks. From testing, an adhesive strength of 0-9 MPa has been estimated for Mineguardriw Dannant, 1997; Sutheriand, 1998; Stone, TENSILE FaURE: Tensile fidure ocarrs when adhesion is lost dong a jo'i sudàce and large rock deformations are pennitted. As the liner is displaced and strecched, the temile loads in the liner material are imd. Ai high tensile loads, the MineguardPY wiil g d l y rupture dong a plane perpendinilar to the Liner surface. This failure mode has been observed in the underground trials and within laboratory testing situations. From testing, an average or mean tensile strength of 9 MPa has been established for Mineguardrrr.
263 3. DLUECTSREAR F m U. Direct shesr fidure d ocair wben the odhesive sîrength ismerthantheshar-ofthe-- ïho6aii~modcirurwucdwithlowrodr dkplacemenîq m M i n g of the ha, and a sheir Siun p h that U papadiailrr to the excavation surhce- F m - 1 teshg the a&ar strength of ù 0.8 to 1.1 MPa [Archi'bald, Ebmver, dmd sbar hilure has not ka obraved in any of the triais or in the iaboratory 6 g. 4. DIAGONAL T W S. FAaURE: Diagd mile hilure caild OCM with d l mcknussdisplraaentr. 45"). This mode of fàilure bu not bem observeci with any of the MuieguarP testing, sim tensile mpture is most often Msociated with sorne sdhesii)n los and with some rodc displacement, These fàilure modes ofthin spray-on liners are depicteci in the folowïng Figure 132. The liner failure is a di.- cesponse to loading by a 100s wedge a hse siabs ont0 the thin membrane. diroct shar through m m bmn. (at unrll displacem~nts) diagoml tonùk hilure of rnombmii. (rt unall disglacofnonts) tensile kilure of m m bmne (rt bige displacern ents) adhosion lou (at mrll or large displrcam ents) Figure 132. Potentiai f~lure modes of thin membrane support flannant, 19971
264 &dl, theadhesive stnmgthddamiaes theultimsiesupportaprityand Wurr modeofthe.. sprayon liner* as foh: (1) - ifadbesion were mruntauied, the lina could fhii by ettha of O dirra sharing or (iii diionai d e fidure, (2) - if the sdhesive bond is lost, the liner wiil eventually fiiil under direct tension loadllig From tlw accurmlated orperieace, ody fhc latter mode (2) seems to be ofprricticrl devance. The dts of the field and hbmto~~ expmments Udicate that adhes'i loss is always associatedwithlinafiiilure. In~diningthelPrgbdtpuU-tests,thetotaidisplacemetst Peak wastypicallytentimcsgceaterthantbetbiclaiessoftk mmôranc beingtested- This indicates t h MinegwirdcY defonns a ConsiderOble emount beforc tensile rupture oaam Furthennore, as the membrane was defotmed, there was sorne debonding ocairring between the liner and the concrete slabs. Coll~equently, aâadhesion loss and the tensile f8ilure mode are the most relevant aspects to considers hm a design point of view. 7.4 Appnwch For retaining systems that are interded to hold rock in place (Figure 88), the design appioach is based on cornparhg the support demand with the capacity of the support system In this manner, a support system's -or the support demand, can be estimated. of déty (FOS), defined as the ratio of the support capcity to DemcMd: The demand that will be exerted on any support system can be examined fbr two scenarios: (1) for scniaurauy-controued fàilure and (2) for scress-driven failure. Ernpiricai, analytical and numerical mehds can be used to establish the demand. As weu, a parametric analysis can be completed to examine the effi of orientation, size and shape, for each of these two broad analytical domains. Chpcity: The capacity of the liner support systems can be estimated hm laboratory and underground test data, and fiom an undding of the fbilure anci support mechanism Analytical and experimental methods can be used to estimate the support capacity, and to compare the capacities for various types of support systems.
265 Stnicturally-Controlled Failurt: The demand is detdned fkom an dysis of the geologid data. Initirilly, structural daîa can identify clustering, whereby definitive joint-- funilier OCCUC. UPng this data, ubiquitous wedge analysis cari be paformed for al1 combinations of joints to determine the critiul wedges. Based on the wedge volumes a d shapes, the demud fbm the support can thcn bc estimateâ. Alternatively, the as-buih joint data can be used to define discrete wedges, to support only the actuai wedges. An alternative study of wedge viability, Viability index, can be undertaken [Diederichs a. al, to determine the qualitative relative viability of the identified ubiquitous wedges. Although theoretical ad unproven as yet, Viability Index assesses which of the kinematically possible wedges pose the greatest staôility wncem (Le. wedges that are likely to occur and wedges that ire likely to be unstaôle) for the design. The design approach for structurally-controlled failure falls into two areas: For well-defined, continuous structure, the demand load is defined as the wedge weight divided by the perimeter (joint length) of the wedge. This d o is compd to the liner capacity (also in terms of force per unit length). For the case of a poorly defined wedge, a point-lod analysis can k used to estimate the capacity offered by the liner system. The liner is acting to support the weight of the wedge in a "suspension bridgen type of mechanism. S tress-driven Failure: Numerical modelling analysis provides a means to estimate mining areas that are likely to be idluenceci by: high stress (rockburst potential), low stress (nlls of ground potential) and the areas where significant stress change is expected to ocau during the mine life. The depth of fiilure may be estimated using an empirical relationship based on constant deviator stress miterion maiser et. al., 19%; Martin et. al., For this analysis, stress-induced brittle failure is initiated for the condition of (a -/ a > 0.4). Note:, a is the maximum tangentid boundary stress.
266 a. is the umfined compressive atmigth of the rockmass. Whn the condition for brittle failure initiation is satisfied, a lin- elasûic stress dysis cm be uscd to estimate the depth of fiiilure around an excavation, Specid Hoek-Brown parameters (d; ) ue used in the elanic mode1 for baie rodc behrviour mser & Tannant, 1999; Mutin et al., 1997, This mcihod is appücable for stress-iduced failure with modartdy jointed to massive roclamus moterial. The f.iled area around the excavation is cstimated by ignoring the nictionol strength component and considering only the los of cohesional strength. For support design, the demand is determined as the dead-weight load of the failed rock materiai. The depth of f~lure also govems the length and pattan of tendon support that must k i dled for excavation stability. The design approach fôr stress-driven failure is as follows: The demand is estimated hm the depth of failure analysis which estimates the depth of stress-slabbing that wirl likely occur around the excavation. The demand load is tiilly related to the loss of the self-supporting capacity of the roclanass, Le- the loss of rockrnass cohesion. The depth of failure can be estimated fiom numerical models, such as PHASES or Examine-2D pniversity of Toronto] with deviatoric criteria (for depth of failure) Martin et. al., 1998; Kaiser & Tannant, For this scenario, the capacity is estimated using a membrane model or fiom a bcm model, as disaissed in the next section. The precise mechamkm by which a Mineguardrrr spray-on liner acts to stabilize the ground in the pai0phery of an excavation is mt wdl understood Thc actuai mechanism of support for ail liners is, in fict, a matter of debrte Md ongoing research, In the absence of a support approach for thin liners, the design has kai much of an art form, rather üw a precise science. Much of the design rationale is barcd on mipinal data a on a monitohg and djusting the support design du~g actual development.
267 INCO7MinesReseerch,incoiiaihotiociwiththeGeo~cs~CniPe,hasconduasd an analyticzl appmach to.. MineguPrdlY spray* liner design rpiierjrirm. This work involved examhtbnofallpmourtatdsutogunmundctsfmdlllgofthc~ mechanism ofthin liners. As weu, dl pevious hboratory testhg chia has b#n u d to estirnote liner capdty 'The recent lak,wtede ud reserrch boitkw shotcrete design [BW & McCrcBth, 1995; Espley, 1995; O'Heam, has a b b&n usd as a cornparison for demad and capacity estimations and for support design approachesproaches Stress and stnidural data is used to define the deriland due to slabbing and weûges, respectively. The weight of the slabs ot wedge, nonnalized to a perimeler (tunnel length or joins length), provide an estirnate ofthe d e d in tams of: f'icepet unit In order to detemine the quired Mineguatd'W thicknss, the liner capacity (fbr resisting wedges or stress-induced slabs) must ais0 be presented in terms of fwce per unit W. Howcver, there are complications in interpdng the I d capacity of a thin membrane hm the types of puil tesis thaî han been pediomwd by Tannant  and Mercer . dbailty arises when estimating the length of the I d bearing support edge 0-e. the &dve length over which the load is carrieci). The Some interpretation of the data has taken piace, as describeci in the next sedion. The effêctive load perimaers were estimated and then the measured loads were converteci into capacities (force per unit length) for dira comparison with the dernands. It must be noted, howewer, that the large-scale pull-testing procedure 9cni;illy measuns the pafomwceofaüna~intaraswithacho~aibstrstemrtall, bricksinthhast. The actual capacity of the lina itselfl without the Ming -ion assessed separately, using dyticai analyses. of the collcrett blocks, mut k
268 The edge support capacity of the Mineguard- liner can be es<imated hm two data sources and using two distinct loûding situations: The adhesion testing daia is used to determine the adhesive load carrying capçrity of the liner, whereby a well-defined wedge is loading the liner. The wedge is assumed to be hily supported dong its penmeter length, Figure 133. UnstaMe Wedge / rift (in section) Figure 133. Liner adhesion capacity: to support a well-defined wedge dong edges The large-de pull-test data results are used to assess the support capacity of the Liner for a poorlydefined wedge. The wedge acts Lice a point-load on the liner. with support offered around the wedge periphery, Figure 134. A point-load analysis provides a means of analytically evaluating the liner membrane capacity. Unstabie Wedge Drift (in section) Figure Liner membrane capacity: to support a poorly-def ned wedge
269 Edgc C.prciîy Edimrtc fmm Adhaion Test Data Wedge support is dso dependent on the tensile strength of the Iuier rmîed. In nrct, a relationship between the liner thickness, the adhesion loss, and the terisile sinmgth can be esbblished to estimate the load-carrying ca~acity of the liner. h can be assumed that at the time of tensile fàilure of the liner, the adhesive and tende strengths arc filly rnobilited. The resulting I d capacity can bc detemineci by converthg the strengths and dnses into faces, Figure 135. As suggesîed by Banett & McCreath [19951, the capacity of the her to resist a wedge Mling under gravity Ming is equivdent to the éffedive bond width Wored by the adhesive strength: C is the adhesive load capacity of the liner (knlm) O* is the average adhesive w is the effective bond width (m) The load capacity is ultimaiely controlied by a force cquilibrium bebveen tensile fbrces due to temile strength and M o n forces due to adhesive strength. An inaeese in &ha parameter results in the liner's ability to handle in& rock-to-liner displacements.
270 In âct. the deformatjan angle of the liner 0.e. an& = 0) is iaausd as the 4dhesion da tensile strerigth W inaeusd C ~ W ~ iruxawd Y ~ araibih pupncren prmidt a cocresponding increase in the -g aprity for the lincr- Figure 135. Limit equilibriurn analysis for thin liners (force diagram) vannant, It is also evident tiiat the adhesive bond width is extremely sensitive to the quality of the rock-- liner interfàce bond and the sûmgth of the subsîraîe material- Thenfore, the in-situ I d capacity is a conam whae gurlity applications are suspect (ie. on wet a dirty rock conditions) and for applicaiïons on weak or -le rocks or materials (Le. such as massive sulphide ore zones or use on bacffill rnaterials). The adhesive caprcity of the Mheguad üna ranges nom 0.6 ta 1.1 MPa (with a man due of 0.9 MPa). Therefore, the load capacity and effèctive bond width am be detennined us* the d t s of the punching-block shear tests [Archibald, 1991;1992]. Loads of 1.1 and 1.73 kn were applied to the centrai biock (with edge lengths of 0.18 m). Two dges of the bkdc wae coated, for a total Iength of 0.36 m
271 Bond Width: w = Fe / (a,. L ) Where: Fe = peak ioad hm the pull-tests = 1.1 and 1-73 IrN a, = adhesive strength = 0.9 MPa = 900 kpa L=totalbondlength= =0.36m Where: a, = the adhesive strength (in MPa) w = the effective bond width (in m) :. C-=(0.9MPa. 1000).(O.ûû4m)= 3.6kN/m Therefore, the adhesive Ioad capacity and the effective bond width are estimated as 3.6 kn/m and 4 mm, respectively. For the most part, the load capacity for the adhesive strength of MineguardTM is not considered to Vary in direct proponion to the Liner thïckness. However, in reality, a thicker liner is more likely to be stiffer Like shotcrete and hence, the effective bond width would iikely become larger, Le. with the load being concentrated amss a larger length. As such, the load capacity provided by the adhesive strength would be h ier for a thick liner, compared to a thin liner. However, since most economic applications of the liner wouid limit the thickness to 2 to 5 mm, the debate of the effect of the Liner thickness on the bond width and the load capacity becornes a moot point. The adhesive strength and the effective bond width values can be used to calculate the largest sized wedge chat is supportable by the liner, without 1 1 added bolts. The main assumption for the calculation is that the weight of the wedge is supporteci dong the joint trace lengths. It is dso assumexi that each side of the wedge has the same length (s), Figure 136. Along Edges 1 1 Figure 136. Wedge dimensions (plan)
272 For the calculation of the maximum size wedge that is supportable with the stand-alone liner. the Fe = Edge Load = Wedge Volume - Unit Weight Assume: y= 27 kwm3 Wedge Perimeter = [(m) s3 42 ] 7 /3s This caiculation suggests that Mineguardm can support a wedge that has equal edge lengths of 0.65 m. In fact, wedges of this size wili be supported and pmented from movhg. Alternatively, the Muieguardm can be perrnitted debond hm the rockmass to allow for some stretch of the liner, Figure 137 (plan) and 138 (section). During this debonding process, the edge length increases proportional to the width of debonding. After an arbitrarily chosen amount of allowable deflection (y = 5 cm), the liner geometry cm be established and the forces that stabilize or support a wedge or block can be detennined. h i Liner support wedge Figure 137. Dimensions of debonded Liner and wedge (plan) The Liner is assumed to provide the support around the outer periphery, with an edge length defined as sz. As such, a new estimate of the Debondeci Liner maximum size of wedge that is supportable by the debonded and stretched MineguardTM can be determined using the same approach as above. Figure Debonded liner with wedge deflection (section) -- 1
273 Assume: O s = quai-sided dge Iength O = edge I«igh of liner, perimder Assign: O h = kngth of- liner, beyonci the edge of the wedgc = 50 cm O y=vdcaidefladiondistancc(s~g)=5an Then: s2 = s h (in rnetres) :. Fe = Edge Load = Wedge Volume Unit Weight Wedge Perimeter = [(m)~~.h]=~f[3(~+i.n)] This calculaîion indiaites that a wedge with side lengths of about 1.0 m can be supported with the adhesive loading capacity of 3.6 W m for the Muiegusrd"< liner if a sag of 5 an is acceptable. Compared to the orst wedge analysig this second dadation gives a wedge perimeter that is 65% larger. The larger site of wedge is schiewble once a degree of ha defledion is permitted dong 4th some los of adhesion been the liner and the rodows around the periphecy of the wedge. The 65% Uvnase in s k is masonable sinoe, with thk second analysiq the edge load is being &ed ova a Lrga pairneter kngth. Intuitively, this suggests that a üna is better able to support Jhsllow wedges that have a large wedge perimeter length, as opposed to steeper wedges that have a mail wedge cdgc kngth
274 However, the capacity also depends on the aiiowable liner stretch as a result of the rockmass deflection. Further analysis of the membrane action of the Liner is warranted, using a ensile support model. In summary* the preceding caiculations indicaie thai an adhesive load capacity of 3.6 kn/m for a spray-on liner offers support capability for structural wedges: The Iargest equal-sided wedge that can be supported without rock deflection is estimateci to have an edge length of 0.65 m. This equates to a wedge perimeter of 1-95 m and a wedge weight of 7 kn. assuming the unit weight of the rockmass materiai is 27 W/m3. If the wedge is pennitted to displace and sag hm the back to a maximum deflection of 5 cm (10%) over a deboadeci length of 50 cm, then a larger wedge can be supported. Specificaliy, the maximum wedge edge length is 1.07 m, for an equai-sided wedge. This correlates to a wedge perimeter of 3.21 m and a wedge weight of 31 kn. These calculations clearly illustrate the support Limitations of MheguardTM in an adhesion mode and indicate the sensitivity of the dtimate load-carrying capacity of the liner, based on the support assumptions used. Speciflcdy, the allowance for some liner stretch and deflection causes the ultimate load capacity to improve dramatically. In light of this, it is recommended that the results of this anaiysis be used with caution, since the estimates are based on some rather generai assumptions and have not yet been substantiated with detaiied experimental data Edge Support Capacity Estimate from Pull-Test Data The edge capacity of the liner can be fwther evaluated using the puii-test data that exists for the Mineguard- liner. There are several sources of data, which are discussed hereunder. Large-sale pull-tests [Tannant, 1993 MIROC tests: (i) solid plaie pull-tests, (ii) perforaîed plate pull-tests, and (iii) punchingblock shear tests [Archibald, 1991 ; 19921, Western Mining Corp., Austraiia, puil-tests Fm et. al., 19993
275 The large-sale pull-est data was analyzed to estimate the capacity of the MineguardTM ber, for design against wedge-type falls of grouod An interiocked panel of concrete blocks was used to simulate a jointed wlanass with the support pmvided by a spray-on liner c&gg The central pull-plate caused the liner and blocks to deform and, 1oad the liner. This pull-testing design simulates point loading on the Liner as a result of an unstable wedge. The pull tests conducted by Tannant did not simulaie ngid biock movements, such as the punching-block shear tests [Archibald, 1991 ; Rauier, the measured loads were associateci with a defod membrane thai acts in tension to resist the applied load, The membrane acts in tension since the concrete blocks are king displaced upward by the pull-plate while the Mineguadm is bonded to the concrete blocks. The highest tension in the Liner occurs near the pull plate where the largest tensile strain is created in the membrane. This is consistent with observations that showed the membrane failed by rupture near the pulling plate, figure High Membrane Tension \ load Figure 139. Locations of membrane tension and mpture in the pull tests Damant, The large-scale pull-test data can be used to estimate the liner capacity for supporthg a poorly- defmed wedge and to dehe the beneficid effects of membrane to rock interaction (see beam mode1 later). Two methodologies were used for h estimations, as described: The pull-testing photos and video can be used to estimate the perimeter of the bbdome" shape of the MineguiVd~ as the pull-plate is levered upward. This primeter length is assumed to be the active zone where Mineguatdm is acting to resist the applied point-load force. The active zone is assumed to be the circular edge of the domed material. The capacity is estirnateci as the peak load divided by the perimeter length.
276 The rupture data hm the pull-testing can be correlated to the sudden drops in load Assuming that the load was lost due to the rupaire itseif, a measure of the force-per-unitlength can be estimated (i.e. A losad / length of rupture). Both the Id drop and the rupture length are measured directly hm the pd-test data records. Data hm four panels was useable for estirnatïng the force per unit length support capacities of the spray-on her (panels 4,s. 9, 11). The interpretation is provideci, as follows: Panel 4: The location and length of the ruptures that occurred dwing pull-testing of panel 4 are shown in Figure 140 (for the hexagonal blocks). This data was correlated to the Iddisplacement curve, Figure 141, to estimate the magnitude of the load drop for each rupture. Crack Lmgth (1) na (2) 0.65 m (3) 0.3 m Perimeter (a) 1.7 m (b) 26 m (c) 3.4 m 262 mm hexagonal blocks (SO mm th*) - viddcamera view Figure 140. Location of major liner ruptures for panel 4 Damant, The active load-carrying perimeter is estimated on Figure 131 as weii. Perimeter lengths (b) and (c) are the outer extents that the MUieguard'fM ber would be acting over. These perimeters yield the most conservative esthaïes for the capacity. The inner perimeter (a) encompasses a region that is slightly larger than the pull-plate. This perimeter value yields the largest capacity for the liner (for the loads that were measured just pnor to liner rupture). This inner perimeter, of 1.7 m. is assumeci to be the active zone of resistance between the liner and the patio slabs. Therefore, a perimeter length of 1.7 m was used in capacity calculaîions with the hexagonal blocks.
277 I I O Disphcement (mm) Figure 141. Load-displacement curve for panel 4 (load drops & peak) According to Figure 113, there is a 10 kn drop in load when the concrete slabs begin to be cmshed (at 40 mm displacement). This indicates that the overail capacity estimaies are representative of two support phenornena. the membrane action of the liner and the bending action on the concrete slabs. Due the liner and block interaction, the capacity estimates should be viewed as overestimates of the actual her capacity itself. Furthemore, the large-scaie puil test arrangement abws for the support hm the iiner to act in a circular region around the applied load Thecefore, the capacity estimate is only relevant to sirnilac loading situations. Using the puil-test information, the capacity calculations for circular membrane support 4) are Listed, Table 43 and 44. * Table 43. Capacity estimate for peak load in panel 4. Peak bad 0 Perimeter (m) capacity (kn/m) The capacity can be normalized to the liner thickness. With this approach, a load capacity of 1.9 to 2.9 knlm/mrn is estimaîed (2.4 kn/m/mm average) for the 8-12 mm thick liner.
278 Table 44. CIprcity estimates for ioad drops in pane1 4. TheSe~es~~oflodUibmanbuvtbrtwznmvlto~naba~f the conaeie bbcks 0.e. in tk vertical direaion)- Again, the capaciîy value (kn/rn) is normalized to the Lina thid<neg, wah the foüowing rra*r: , 2.9, ad 4.4 Wdmm The average value is 3-4 kn//mm. Pmrek 5.9 and II: Aswiththemahoddoeyforcaldstingaapritywithpuwl461.,üieymeprocedurewur usedforpanels5,9and 11. ïhesepenelswae~~ll~t~dedwithfedangularbbflyriiihathan the hexagonal blocks of panel 4. The active perimeta wu estimated to k 2.3 m, which is 35% larger than the meter esiirmic for the densa pattern of hexagonal bl&. This larger due was selected based on visual observations of the zone of block-to-her interaction and on the block geaneiry/pattern The copacity data is summarîzed in Table 45. Table 45. Estimated load capacities based on large-sale pull-test data As with the previous tehg the capacity data Wrn) is normilized to the thickness (to vravd for the variation in the appiied thickness). An average value of 5.3 Wdmm was oboincd foi the peak load capacity, and an average of 7.5 JEN/m/mm wrs estimated for the load capady basecl on liner rupture.
279 The complete set of test results are s e in Table 46, with the load nonnalized to the liner thickness. Both the peak load (acting over a circular perinieter) and the liner rupture I d drops (acting over the damage length) are provided Tbe results are based on a limited number of tests, so caution shouid be exercised in applying these values for design purposes. Table 46. Mineguardm load-carrying capacity based on the large-scale pull-test data Panel 1 Thickness (mm) 1 Method 1 Load Capacity (kn/m/mm) 4 8 to 12 Rupture Ioads 2.5 to to 10 Peak load 1.7 to Peak load I Peakload The average value for the peak load approach is 3.4 kn/m/mm, while the rupture analysis yields an average capacity of 5.4 kn/m/mm. A consemative value of 3 kn/rnhn.cn is suggested, for the condition of loading h m a poorlydehned wedge, where a liner acts dong the wedge periphery MIROC Pull-Test Data i) Solid Pull-Plate Tests,. The MIROC puli-plate test data can be analyzed to estimate capacity in tem of force per unit length. The puil-tests conducted at INCO's North Mine used solid 125-nun and 254-mm diameter plates and perforated 254-uim diameter plates [Archiiaid, Similar pull-tests were perfomied with concrete-slab substrate matenal [Archibald, I9921. Pull-tests using the solid plates resulted in faiiure of the MineguardTM liner around the perimeter of the plate, at appmximately 40 to 50-mm of displacement. With a thin membrane (2 mm thick), failure was not likely to be due to shear stresses, but rather failure due to stretch and tensiie rupture.
280 Furthermore,the~losdsintheseMIROCtestshPvebeenconvertedintocapacitieSby dividing the peak Iood by tik phte pimeter- This is an ova CStimsiteofthecopPcitysüicethe load was ükely distni ova 1 lwger pahetcr distance due to debonding uwud the plate edge during testins No measurements were available for the debondeed distance, to tstimate the actuai M i g perimeter. As such, the capacities in Table 47 are basai on the piate perllnecer and are normalized to the liner thickness. Table 47. MineguarcP capacity based on MIROC solid plate pull-tests Test m dia. (dg) dir (dg) mm dia. (dg) ii) Perfwded PuII-Plore T i : 'The MIROC pull-tests with paforated plates (aî INCO's Nath Muu) meipirrd both the adhesive strength between MincguardCY and the n>ck, as wdl as the suspension effect beyond the plaîe perimeter.
281 Theadheoive strengîhofthemimpwp linacan becrtirmtedbomthe bdr merairrd rt smdi displacements (40 mm). 'The adhesive s&cngth khmai thc MkguanP a d the subsnate is estunnted by dividing the pak kd (at d l displuemaits) by the surfrce area of the plate, Table 48. Table 48. Adhesive strength of MineguarcP with rock substrcrte [Archibald, Test 254 mm dia (dg) Peak Load m 20.1 (mm) 3.26 Area (m W a ) 0.4 The Liner capacity is estimated as the ratio of the peak l d to the perimeter of the pull-platc, OC 25 knïm Nonnalized to the liner thickness, a capacity of 7.7 Wm/mm is determined (for a point-loadhspension support mode). iii) Ikmhiq-BI'k~ T'es&: Laboratory tests were mnducted to evaluate the shear s~rength of the Mineguard'W liner. nie test arrangement consisted of three CO-e blocks, abutied togeiher, with the liner sprayed across the block sutfaces. The outer blocks are fixed and the central block is loaded and pished downward, Figure 142. The details ofthe testing were presentd by MIROC [Archibald, Figure 142. Punching-block shear test [Archibald, nie test arrangement was designed to examine the Cnéct of having joint infilaotion (between the blocks) or not.
282 The results fm no joint infikation shouid bc comparable with thc rdyi plrtc piu-fests. In t h scenario, the MkguanP LULQ acts in taision to support the disphcd caitnl blodc Conversely, with joint hfihdon (ad m mntinuous membrane &kt) a vilue of the skar strength ofmineguarcp would be estimoted. Based on the du m e d in the MIROC rrpatr. the fdowing liner load-cmyhg apadk~ (Table 49) and shear sûmgths (Tabk 50) Tor MkgumP wsc cairmtcd. 'Lhc a- capacity is 3.65 kn/m/mrn fw infiitnüion d membrane.ction. Test Sudke Table 49. Capacity estitmated fiorn punching tests PeakLaad 0 >1.73 Thickness (mm) 2.36 Petkder (ml 0.36 Capacity Wdm) >2.0 kd Slutkce >LI >2.1 I Mit. + Men Infilt. + Mem Table 50. MineguarP shear strength estimated by punching tests Test Infiltration Infilsation The tests of both joint infwation plus membrane Sier action does n& prwide a clear load capacity estimate. This test is measuring some aspect of the shear strength as well as the membrane effect of the liner Australian PulCTut Data Large-sale sdid Peak Load Depth (mm) Perimeter (ml Shear Stmgth W a ) have been perfonned in Austnlia [Fh et. al., to compare MineguarP with a latex mataial, Everbond. One set of tests d a d pli-plate (1 m2) with a surface coating ofmineguarp, with a concxete slab as the substrate
283 The pull-testing revealed a palr lod of 70 W. A disaission with the application pasoaael indicates that the membrane was abut 4-mm thijc rround the plate [Cahcü, perscommun, This yields a lod a+ty of about 4.4 Wdmm. VariousapprosdierwercdtoenminetheloadcspsPty~fMineguard"c~ Iniapastioaof the test data indicates thpf the Iuia as by adhesion loss and tende rupture of the membrane. The test data was processed to obtaui Id capacities in terms of fwe pcr unit kngth 1) Adhesion testing yielded a losd capchy estimate of 3.6 kn/m for supporthg a welidefined wedge or block. Using this load capady, two additional analyses were COndLlaed: (1) det ernunation of the largest size of wedge that can be supported by the liner, without displacement, and (2) dei ennination of the kgest site of wedge that can be supported if some debonding and -ch occurs with the Mineguard'w Iiner- The calculations indicate that the MineguarP Liner has sufficient losdenyhg capacity to support small wedges (with an edge length of 0.65 m and a block weight of 7 IrN) mthout rockmass deflection Comparatively, with allowances of 5 cm of deflection and 50 cm of debonding, the liner has inaeased capacity for supporting a larger wedge (with an exige length of 1-07 m and a block weight of 3 1 H). 2) Pull-testing data yielded a range of capacity values h m 1.7 to 12.5 Wdmm. This data was derived 6om GRC's largesc.de pull-tests, MIROC'S pull-tests and punching-block shear tests, and an Australian pull-test. With the large-scie pull tests, the peak loads and rupture load losses were used to estimate the capacity with point-ldi and support arwnd thc periphery. Thc peak load estimates varied fiom 1.7 to 8.5 kn/m/mm, with an average load capacity of 3.4 IcN/m/mm. The rupture capacities varied hm 2.5 to 12.5 kn/m/mm, with an average vaiuc of 5.4 kn/m/mm. The average apicity, using both sets of data, is 4.4 W/m/mm.
284 Atta fihering the puli-test datq an average lod aprciry of32 Wmlmm is achieved fm the liner acting to resist a poht-load. Atter some debonding and st- the Liner ultimately M s under d i i tension Basai on the tirnitad data, the suggested due for the load &ty (tensile) is 3 kn,/dmm This cepsaty is appiicable tiw poody-definad wedges whereby the lina provides support h g the periphery of the wedge base- An d*col approach, using (discussed later), can validate these results. A capacity of 3 W/m/mm would over&ate the MkgunP luier mpcity where the liner is oniy providing support dong two edges of the tunnel (parallei to the ds). The anaiytical analysis thaî is used to address the capacity of a liner, whn the support is ody provided dong two tunnel walls, is dled the membrane aqput d i (discussed h), Table 5 1 sununarizes the suggested design values for a 2-mm thick membrane of M i n e - for support of a welldefined wedge (adhesive capacity) and a priydefined wedge (tensile failure). Table 5 1. Summary oemineguard design values Parameter Tensile strength Adhesive strength Effdve bond width Range of Vducr 8to 10MPa 0.6 to to 5.4 mm Assumai Design Vdue 9 MPa 0.9 MPa 4.4 mm 3 to 3.9 kn/m/mrn 3-6 IcN"m/mm * (tensile hilwe)
285 752 Membrane and Beam Chpadh~ The edge capaciry of a thin liwr has been dûcussed whereby the iiner acts to support a wedge that is either M y defined witb joint traces or is poorly-deked, as a point-load For both situations, it is assumed that the liner is providing 36ûdegees of support around the edge or base of the load. Edge capacity estimates were derived brn laboratory tests and some analyticai equations, for adhesive capacity and for tensile capacity of MineguardTM. These estimates can be used in support design where loading is a function of the stnictud geology. For the stress-driven domain of loading, another approach to assessing the spray-on liner support capacity must be considered. For a given drift with stress fracturing, Figure 143 a spray-on liner Liner Support dong Dn Aburment 1 Wall support system must have the capacity to hold up the dead- weight loading. The support rnechanisms are beam d o r membrane actions. Figure 143. Stress-driven loading system For the membrane mode1 and the beam m u, Figure 144, the tensile strength of the liner is the main factor for esthaîhg the load-carrying capacity. The tensile strength is required to resist rupture and for distributing the load across the liner and rockmass. For MineguardfM, the established tensile strength, a, is 9 MPa wrylon, Applied Load Applied Load MEMBRANE BEAM Figure 144, Membrane and beam models for assessing liner support of fkctured ground. 264
286 Membrane Mode1 As summarized prieviously, tbe load capacity de- from the large-scale pull-test data is applicable for support design against wedge-type failure. It is assumed that the load is distributed around the circumference of the wedge. There is an obvious question, however, whether this capacity would be valid for design of stress-slabbed materiai in the back of a tunnel. As shown in the above Figure 143, it is likely that the liner support is ody king provided dong the tunnel walls (Le- on two-edges) and not fully encapsulahg the stress- fi-actured gniund. An intuitive estimate is to reduce the capacity by 5Wo for application to stress-dornain support design (Le. reduce the capacity hm 3 kn/m/rnm to 1.5 kn/m/mm). This is based on the diffetence between '360degree support" vs. "180-degrees" (in a manner of speaking). A more analyticai estimate is discussed kïow. In reference to Figure 145, the area for circuiar loading is equated to the area for rectangular loading, with a value of m2. This area value is based on the domed region hm the large- scale pull-tests, with a radius of m. Assuming that the load hm a wedge is distributed on ail sides of the block (in a complete circle), and assuming that stress-fhctured rock wiii only be supporteci dong the drift walls (on two sides of the rectaagie), the ratio of perimeter-to-area can be estirnated for the two cases: (i) for circular loading, the ratio is 5-46; (ii) for the rectangular "strip" loading, the ratio is This is a ciifference of 44%. As a result, an approximate load capacity for liner support design of stress fktured rockmass is 1.7 kn/m/mm, 1 1 Figure 145. Circular versus paraliel-wall support To test the validity of the load capacity estimate for stress hctured ground, the foiiowing cable analysis can be useci, with a uniformly disui'buted load The Mineguardm liner is assumed to provide membrane capacity, with two-sided (parailel or sub-parailel) support, analogous to a cyiindrical model. The Liner can be madelleci as a suspension cable with a uniforxniy distributed load acting dong its length.
287 The analysis is describeci by Beer & Jobton , with reference to Figure 146. The cabie hangs in the shape of a c we and the force in the cable (at any point) is a force of tension, T, acting tangentid to tbe cable. The cable is fixed at the end-points A and B, with the lowest point of the cable at C. The vertical distance between A and C is the deflection of the cable, y. The horizontal distance h m A to C is defined as the half-span, x. The resultant load force, W, accounts for the disiributeci load between A and C. This load acts at (x/2). For the case of support design for stms fnctured ground, the distributed cable load îs equivalent to the dernand value from a depth of failure andysis. Figure 146. Force diagram for a unifonnly distributed load on a cable Using the definitions provided by Beer & Johnston [I981], the foliowing relationships can be established for the unifody loaded cable (liner): MaximumTension: T=(T.~+W')~ =(ot area ) Minimum Tension: To = T cos 0 (where: W = T sin 0 ) Load: W=(p-x)=(T-sine). Deflection or Sag: y = ( x )/ ( 2 T ). for MA = O (Equation 6) For this andysis, an aliowable deflection of the mkrnass and ber in the back of the tunnel must be assigneci. This value of sag should be based on the acceptable limitts currentiy used in the mining industry. For instance, excessive sagging of the back of an excavation woutd cause concem for most mine operators such that the area would be reconditioned. From experience, a 5% sag limit is assigneci as a reasonable limit for allowable deflection. This percentage of deflection is equivalent to a downward deflection of 0.25 m over a total excavation span of 5 m.
288 Using a 5% aüowable sag limit, the capacity of the MineguaraCM liner can be estimaid. As weli, the depth of failed rock that is supportable with this capitcity can be determine& Based on an aiiowable vertical deflection or sag of 5%: Then: y=o.osx-2=0.10x Substituting Eq. 7 into Eq. 6: :. p = ( T / 5 x ), where x = half-span For a, = 9 MPa wrylon, 19981, T = 9 C;N/dm.cn.*. pdr=t/(5x)=( 1.8/x) k~/m'/mm Assume: y = 27 kn/rn3 (rock unit weight) Then: djdk=(l.8/x)/(27k~/m3)= (l/lsx)mlmm :.the load capacity and the depth of supportable rock is a function of the span, For membrane support (based on distributed loading dong a cable with a Liner thickness of 10 mm), refer to Figure 147. Soan (metres) +p (distributed) d f (distributed)- right axis Figure 147. Load capacity and supportable depth of failed rock for distnbuted loads 267
289 For mmparison, the large-scaie piii-test data am k apminsd using the fdae Tor the able (distn'buted Iding) Maiysis. This comparison is seen as a validasian acercise. Based on the capady estimdcd fiam the iarge-scaic pull terrts [Tamant, lm: Load: W-=3Wm/mm Since: w=p-x :. p-=(3/ x) ~rn'/nun Since: p eibit= ( 1.8/x), as hwnbefore.o. Then: (pw)= (pcaic-1-67) This result indicates that the large-de load capamty is 67?A hi* than the d ue of the I d capaeity determineci by the distni-id dytid mechod. Similarly; Assume: y = 27 wm3 (rock unit weight) :- (cl,-) =(p4ru)l(27knlm3)=(1.671 lsx)m/mm :. (4-) = (dfd-1-67) This secund caladation indicates thaî the supportable depth of failure for pdy dehed wedges or with stress aacaued graud should be estjmaîed with the disrriôuted ioad a point-id approach The large-scale pli-test over-estimates the supportable depth of fàilurc by 67% for the lodig of a pooriy de- wedge or stress fhctured rock 7521 Point-Laad Anmis The analytical a p p d to dma$hg membrane capacity by using classicai mathemdics can be fbther explored for a cabfe with a cotlcenûated central point-id. This approach is valid for the case where the wedge is poorly defined, stnicturalty. The point-load calculath [Beer & Johnston, for the temile sûength of MineguW is estimated, Figure 148.
290 It is assumed that a 5% deflection limit is ailoweà, and thaî the liner Lias debcmded over a 1engi.h ofx = 50 cm. The load, W, is applied at point C. The deflection is represented by y = 5 cm. The support capacity (resistance) is W/2, for a given span of x. Figure 148. Point-load force diagram From the force diagram, the foilowing relationship is developed, as applied to a ber: Where: T = the tensile force in the liner o, = the tende strength of the liner = 9 MPa area = the area over which the load is acting ( = a point load, for this case) 0 = angle between the liner and the horizontal plane Assume: y = 5 cm; x = 50 cm :. 0 = 5.7O :. W = 2 (9)/(sin5.7l0 )=: 1.79kN/m,11ll1l :.the max aiiowable point-load is 1.79 kn/m/mm (for 5% sag and a, = 9 MPa) For: t = 10 mm and y = 27 kn/m3 (rock unit weight).-. W = 17.9 kn/m for 10 mm thickness.: wedge volume = 0.66 m3 (per metre span) The result of the point-load analysis, for a liner thickness of 10 mm, is shown on the following Figure 149.
291 C \ i Supportable Depth 1 t 1 u of Broken Rock O Span (metres) - W (centre point-load) in MWm WI2x Figure 149. Load capacity and supportable volume of rock for a point-load The resulting point-load capacity of the liner is equivalent to the result of the distnibuted load analysis. The liner capacity for a point-load is determineci as 1.8 kn/m/mm, or a 0.66 m3 volume of rock Based on the analysis of the distributed and point-load chia, a depth of failure of 0.2 m is supportable with a thin liner assuming a 3 m span, Figure 149. This result is dependent on the unit weight of rock being 27 lnm3 and no adverse stress changes and ground detenoration. In addition to the point-load calculation for a cable, an alternative method for estimating the liner capacity due to point-loadhg is to use a Srnichuai Engineering approach to plate theory. In this method, a centrai point-load (P) is distributed over a plate, wbich is repcesented by two strips, Figure 150. Figure 150. Point-Id distributed over plates
292 Each strip has a given width, w, and a thickness, t. The loading on the strips is shed to four supports (the bolts holding the membrane) such that each anchor c& one-fourth (P/4) of the total load. The edge capacity is estirnated as: Capacity = Load / ( 4 w t ) The data hm GRC's large-%ale tests, panel 4, can be used in this equation. The input values are: a peak load of 40 kn, 8 to 12 mm liner thickness, and a plate width (w) of 50.6 m (haif the boit spacing and half the spacing between the test hme legs). A value of 21-7 kn/m/mm is estimated with this data This analysis suggests that the capacity estimate hm the large-sale puli-tests over-estimates the liner's capacity by 67% if the liner is acting as a membrane with a concentrated point-load, SUMMARY OF RESULTS FOR MEMBRANE MODELS: The cable analyses (with a distributeci load and a point-load) as weil as the above approach using plates and support columns estimate a liner capacity that is 40% lower than the value derived from the large-scale puil-test data. The large-scale pull-test capacity is higher due to the interaction of the concrete slabs with the liner and due to the lower load area per edge length ratio. Based on these analyticai analyses, the estimated membrane capaciry of MineguardTM is 1.8 W/m/mm- This value assumes a tende support mode and a total aîlowable deflection or sag of 5%. This value should be used for support design where the liner is only providing support dong parailel tunnel wails Beam Mode1 The higher I d capacity of 3 kn/m/mm fiam the large-scale puli tests indicates the importance of fomiing rock bearns or arches, for increasing the capacity of the Liner and rockmass system. The beam modei (whkh is created hm the continuous membrane coverage of her across the rock surface) is Mer explore& analytically, to estimate a beam cupcify for support design. This type of support design is applicable to stress fiactured ground with the added influence of stnictumi discontinuities.
293 It is conceivable that a spray-on liner cm effitively bond the strpss knired slabs together to form a reinforce. rock arch. This codd be further enhanced with a pattern of mkbolts, depending on the anticipaied &mand. With the beam model, Figure 15 1, a series of bricks are adhered together dong their base with a ber of thickness, t. The brick length, 1 b, thickness, h b, are variable and WU influence the overaii capacity of the beam smicnire. The span of the beam is &&ed as 2x Figure Beam and membrane model For the defined beam model, the following relatioaships are cietennineci: Assume: no crushing of the bricks during loading.*. ttc=i-~tl Mm-=(Px)-(px2/2)= 2.O. ~ t.*hb=m-=(px t 12) :. p=(2crt-t.ht,)/(~') -(px2/2)=(px2/2) [Equationg] The data from the GRC large-sale pull-tests can be examined using this relationship. Specifically, the data for the panel 4 test can be examined, as foiiows:
294 a Assign: a, = 9 MPa; t = 10 mm; 4, = 50 mm; x < 0.6 m (panel 4 data) :. p > 25 kn (the beam capacity for pl0 mm) :. p k ~/m~ per mm of liner thickness The analysis iodicates h t the i d capacity froxn the beam and membrane support mode is 2.5 kn/m2 per mm of liwr thickness, for the blocks (or beam) king H) mm in thickness. The analysis can be repeated for panel 5, where the thicker rectangulat blocks were tested with a Mineguitfd- liner (t = 2 to IO mm). Assign: G = 9 MPa; t = 6 mm; :. p = 27 kn (the beam capacity for t = 6 mm).: 4.5 kn/m2 per mm of liner thickness = 90 mm; x = 0.6 m (panel 5 data) The analysis indicates that the load capacity fiam a beam and membrane support mode is 4.5 kn/rn2 per mm of Liner thickness. for a beam (or block) that is 90 mm in thickness. Beam theory States that the capacity will be improved with thicker blocks, as demonstrated above. Since the blocks used in panel 5 are 44% thicker than the hexagonal bricks in panel 4 testing, the ciifference in the beam capacity for the wo panels is also 44%. The overall capacity of the bearn is further dependent on the thickness of the membrane Liner. A thicker membrane improves the beacn and membrane support capacity. In an analysis of the large-sale pull-test data, it is interesthg to note that the peak loads (norrnalized to liner tbickness) were 33 to 38% higher for the pull-tests on the rectangular blocks, as cornpareci to the hexagonal block tests. This was consistent for all test scenarios: (i) the thick liner, (ii) the thin liner and (ii) the taped-block application. It is also interesthg to note that as the bricks were crushed during the puil-tests (with defonmtions greater than i5 to 50 mm, approximaîely), the load capacity gradudy decreasecl.
295 The gradua1 load drop for each test is clearly evident on the post-peak portion of the laddeformation cwes for the tes~g. This portion of the test was accompanied with audiie cnishing and snapping noises of the paîïo slabs. There were also sudden load drops associated with distinct cnishing, snapping and sbearing of the edges and corners of the patio slabs. The loss in loadcarrying capacity (either gradudy or suddenly) is assaiated with the cmshing of the concrete slabs. This cxushing action causes the value of hb to be reduced, which in tum reduces the overall beam and membrane capcity (i.e. the effective height of the patio slabs is reduced during ioading, due to cmshing). These results are important for support design, especially for blocky &or stress fractured rock conditions. In fact, a bolt-and-liner support system could provide significant capacity the tendons pin rock slabs together while the liner prevents loosening between bolts such that a thick, reinforcd beam is created. Figure 152 demonstrates the impact of the beam thickness on the load capacity, assuming there is a membrane Liner of 10 mm thickness. As shown, even the creation of thin bearns (c 1 m in thîckness) bas a ciramatic effect on improving the support capacity, particularly for spans less than 2 m- This graph also illustrates that a wide bolt pattern cm be used if and when it is expected that there is beam action (h b >> O) in an excavation. O 1 Span (metres) 2 3 -hb = 50mm -hb = 75mm -hb = loomm - hb = 200mm -hb = 400mm +hb = 600mm Figure 152. Load capacity estimation for various beam thicknesses
296 As an alternative to aiiivernional bits, sasen anâ shaccrcte, the podud must have the capabiiity to pavidc adapte lod-krring apoaty fa wdges, rtrry SLWhg and the rock buntuig corditiaasaicountaed~~c0. R e s u h s t o ~ ~ ~ s University, INCO's mdeqmud truls ud GRC's -de puil tedng with INCO's Miacs Research DepartmnS inditates to perform weîl as a retaining dement in roclrburst prone amas. the appiicability of using MkguanP to support dges and Untortunatefy,~km~derr-cut~toddamimtheerad~Ofalnia,~is.. there an exact means of determinhg the inherent rocbripss streagth and Ming conditwwis (ie- the demand). For this and dm rcasons, the trend in mining has been to muxt to anpirical support design methods. Empincism is the basic d e of "if it works in a given apptication, it is bwnd to s u d in an application with similar parameters". In the last few decades, much of the geomechanics research has oentred on developing anpirical methods to hate the mechanical properties of the rocbnass. From this wodq several rockmas classification schernes have been developed to the relative integrky of the rock, using a range of input parameters. Some of the design charts have ben developed speciticaily for civil engineering projects, although there is a growing fiom underground mining successes and failures, to provide valuable information for drift and stop designs. The popularity of empirical design methods is likely due to the relative egse of application of such approaches, -y some standard niles are followed or a value is read h m a chut oc table. The design method is simple and based on an expandimg how ledge. of expience and In general, if your design parameters coincide with parameters of examples used in the crdon of an empirical chart, the un- in a new design begin to vary h m higher and the level of confidence drops. associated with the resuiting design W low. As parameters the parameters in the daîabaq the mc&ahty becornes
297 Despite the ladc of aimnt rmt basic coniprrioau can be made using the stpndsrd support recomrnendaîions asociaîed with the Rock Mass and the Tunneiiing Quality Index (Q) rbckmass classification systems originally proposed by Bieniawski [19î3; 1976; 1989; a d Barton et. al. [1974, respectivvely. The Modifieci Rock Quality Index (Q'), whkh was developed for the design of tunnels in rock parton et al., 19921, can also be used to assess the roie of thin Liners as a support component in underground herdrock mining applications. Whiie providing a usefhl starhg point for thin spray-on liner support design, t h ernpiriad designs!àll short si- a Factor of Safi is not known There is only O* clear distùidion: those cases where the FOS is greater than one (for stable excavations) and those cases where the FOS is less than 1 (when fkilure ocairs). Despite sorne shortcomings, rodonass classification offi a means to consuit with empincal charts for support design. RMR ducs in the INCO (Ontario Division) mines tend to be in the 35 to 60 range (particuiarly for production headings, where blascing has Uifluenced the integrity of the rock). The majority of the dmlopment heaâings, in comptent host rocks, have RMR values in the range of 60 to 80. Likewise, the Q' values range between O. 1 to 1, for some distinct zones, while the rnajonty of the Sudbwy rocks are in the upper range of Q' = 1 to 10. Some development headings in the INCO mines have been unsupported for ddes, and these areas are stiu in excellent dition. The raîing fbr the host rocks with these heridings would be vesy high (RMR > 80 and Q' > 10).
298 The Rock Quality Designation (RQD) rockmass classification Wre et. al, 1967; 1%9] is a routinely collected value at INCO, hm diamond drill cores. This value is usudy only very poor in rockmass areas where there are signifiant stmctural influences, such as dykes or fauits. Otherwise, RQD falls into the 70 to 10% cluster for most rocks in the INCO mines (at low to moderate depths). At depths greater than 1500 m, approximstely, the idluence of high stress can causes disking of the core, which makes the in situ RQD diflicult to ascertain. Rockmass classification schemes were developed to chatacterize the strength and deformation behaviour of the rock Bieniawski and Barton et. ai developed their classifkation systems for estùnating turne1 support- Four common design charts that cm be used to assist in support design for tunnels are listed as foliows: 1. Merritt's DesignChart 2. Bieniawski's Design Chart  3. Barton's Design Chart parton et. al., 1974; Grimstad & Barton's Design Chart  The TumeLing Quality Index [Barton et. al., 1974 Barton, 1988; can be used for rockmass classification and for determining the no support limit or maximum unsupported span. The Stability Graph Method (Mathews et. ai., 1981; & many others] can be used to assess stabiiity of stopes. More recently, cable bolting design charts were developed for underground mining situations [Ponin & Milne, 1992; Hutchinson & Diedenchs, The modified design chart for drifting by Grimstad et. al.  can be used to estimate support categones based on Barton's original charts [1974; 1988; This chart plots Q versus the excavation span (Le. span is nomialized to the Excavarion Support Ratio, ER). The ESR value relates to the intended use of the excavation and the degree of safety that will be reqwred from the support system for excavation stabiiity. ESR values chat are common for underground mining are in the range of: (1) 3 to 5, for temporary mine openings, and (2) 1.6, for permanent mine openings. As expecteü, the assigned ESR value is much lower for civil engineering projecrs, due to the life of the project and a high level of safety requïmi.
299 On this chart, the level of support gradually increases relaîive to the decreashg quality of the mkmass and relative to the critical span and Me of the opening. As the expected demand increases with lower quality tockmass conditions, the support recommendations inccease hm unsupported, to spot bolmg, to pattern bol& to paaem bolts and shotcrete (again, with vaiying additives and thickness requirements as the dernaads are increased), to the upper support level of cast concrete. The upper-most zone of the chart (exceptionally poor rockmass quality and excessively wide spans) is the worst-case zone that is not supportable. For the generalized tockmass quality ratings for the Ontario Division Mines at MC0 (Q' = 0.1 to IO), the no suppm limits can be calculated using the relationship developed by Barton et. al. : The values in Table x are the maximum spans that can be excavated and remain stable without support, for the given Q rock conditions. These values can also be estimated using the design chart by Barton et, ai. (19881 with the region defined in the lower-boundary. For the Table 52, the stress reduction factor (SRF) is considered to be equal to 1.0 and the excavation stability mihg was assumed to range hm 1.6 (for permanent mine openings), to ESR = 3 and 5 (for temporary mine openings). For this analysis, a SRI? = 1.0 provides an estimate whereby Q = Q', as long as the rockmass is dry. Table 52. No support limit spans (in m) for a range of Q and ESR values
300 Based on the no support limit data in Table 52, a boltless and thin coating of MineguardTM (2 to 4 mm in thickness) could be used to enhance safety in permanent mine excavations with spans of 3.2 m or less. This recommendation is oniy valid for a rockmass quality of Q and for moderaie stress levels (where SRF = 1.0) and where there are no detrimental water effects in the drift. As well, this is only valid for conditions where the mining induceci stress changes do not adversely affect the heading. Specificaiiy, areas of possible stress relaxation would not be candidate sites for using a stand-alone Liner support system. Ah, areas of rockrnass degradation due to blasmg effects, water influences, and micro-seismic activity are not appropriate for the thin liner support, without bolting Support ResureEsh'uiltrtes According to Grïmstad and Barton , a relationship exists between the Tunnelhg Quality Index (Q) and the permanent support pressure in the back of an excavation. This calculation can be used to estùnated the pressure demand for a range of Q values for NCO rock conditions, to compare with other appropriate support capacities. The equation is as foliows poek et. al., 19951: (Equation 10) Where: J, is the number of joints in the rockmass J, is the joint roughness value Q is the Tumehg Quality index P,f is the support pressure in the back of the heding [ kg/cm2 ] = P d-,j An analysis of this equation shows that the support pressure will decrea~e as the roughness on the joints is increased. As wei.1, the support pressure increases when the number of joints increase and when the quaiity of the rockmass is deteriorating.
301 Assuming typical conditions in the rockmasses at INCO's Ontario Division mines, the J, is generdy in the range of 1.0 (smooth and plana) to 1.5 (rough and irregular), to 3 (rough, irregular and undulating). The J,, value ranges h m 12 (three sets plus random), to ihree joint sets (9). to 6 (two joints plus random). Using these values, and the range of Q values and ESR vdues previously discussed, the suppott pressures can be detennined for the WC0 hardrock mines, Table 53. Table 53. Support pressures (in MPa) for typicai INCO rockmass conditions 1 Estimateci Support Pressure &Pa) I Suppon Pressures Assume: J, = 9, SRF = 1.O and J,,, = 1.O Assuming a joint roughness of 1.0, the no support limit and corresponding estimated support pressures can be plotted for a range of Q' values (O. 1 to 1 to IO), Figure 153. l O Span (matres) I +No-Support Iimit [ml Figure 153. No-support Iimit for typical INCO rockmass conditions
302 Where: P~oqriLyi~thecaplcityofthe~portsystem,inMPa P M ~ is determllied M i?om Hoek a al. [1980b in temu ofmn for bolhg s2 is the supportable area or bolt spacing, in mz - Assign: P~-iaa=0.11MNfor16mmdiamet~~~. PM-=(0.11MN)/(2.3 m2),since spacing=lsrn(=5ft).o. P M- = MPa.* 16 mm rockbolts on a 1.5 m spacing provides a support pressure of MNh2 This dculation can be repeated for medium rod<bdts which have a puü-out load of 0.27 MN. It is assumed thaî - these bolts wiu be place on the same spachg as the 16 mm dimeter bok Assign: m P = 0.27 MN for 25 mm diameter rockbolts :. Pw~=(0.2SMN)1(2.3m2),since spacing=l.srn(=sft) :. P = O.1W MPa. 25 mm rocl<bolts on a 1.5 m provides a support presure of0.109 MN/^^ From this analysiq a support cspsoty of O.CM7 MPa csn &dvely support an ma of2.25 m2, or an equivaient span of 1.5 rn The MineguarP liner can provide the support cspraty f9r spans on the order of 1.5 m, to retah the roclanass between the boits.
303 This is valid for poor quality grouod conditions (Q' = 0.1) with snooth and planar joint surfka. This does not consider the additional degradation aspects of joint water and stress relaxation. As well, this maximum unsupported span (for liner support) estimate does not consider the benefit of using bolts and a iiner to create a reinforced beam In this case, the capacity of the system is pater than the capacicy of each component part. This is discussed furcher in the next section. in order to estimate the support capacity for a thin sprayan liner, several aoaiytical and empirical methods have been investigated. The following modek were used to examine membrane and beam support hm a liner Membrane Model: with two cases: (1) distributeci loading, and (2) central point loading on a cable. BeamModel The capacity estimates fiom these k analyses can be overlain with the capacity estimates h m analysis of the pull-testing &ta and fiom empirical approaches to support design. The summary of the analyses are provided in the Figurie 154. : SQan (ml -üistributed Load (Cable) -Point Load (Caôie Centre) -0-Beam (hb-543 mm) - c Ecige Capacity = 3 kwrn/mm.-q'(rnin) = O. 1,-QNo-Support limit -df(astribuîed) - nght ais [ml Figure 154. Cornparison of support design techniques for tbin liners 282
304 k e are many intangible &écts stmmdng the support mechanisan of ünas th0 am Wavlly impossible to pmcklyy For example, the folbwing highlight the intangible bene- of an impcrvious spray-on The impervious nature of the liner prevents weaîherhg Md chernical &aiorption that occurs with the presence ofwata in excavations. The membrane action of the liner maintains the cohesive and fictional strength of rockmass, by ailowing the rochass to ad as a beam. The preravation of r d bridges aids to maximize the self-supporting action ofthe rockmass. Consequently, the support design must ansider these bene&% in reference to the underground environment that the support is being designeci for, i-e. the size, shape, depth and the siand-up tirne for the sccavation. Also, JI aspects regardhg the stress anci stnichual d e d s mut be clearly dehed and considered, 7.81 Limitations Since the following support guidelines are based on generai assurnptions, caution Jhwld be used until fùrther validateci is completed. In f a the laboratory and underground testing results and the mmpanying adyticai design considerations are prelim'i whaeby the folbwuig limitations apply: The support design represerited in this thess has ben based on typical harbodc sttengths and rocbirpss chuacteristics fbmd in the Sudbury basin mines. The rodc is gemdkd as beig poor to good, with Q' = 0.1 to 10 or better-
305 Failmes of the IbhqunP lincr have omimd whm the rodoiuiss is vay weak For instance, in ippihîbs with massive dphides, il u wmmon fm the ore to k vay aiable andweak AlthaighthcbondbehHcnthe~udtheulphidesisvayg~itU possible for the ore itselfto brak aprt ad peel fkom the excavation ôcnmhy. This is les of a problem for ~now vein mining where the liner is able to bridge across the higbgde ore string- to the adjacent ho* rocks. The liner effidively spans the weak rmtaiil to provide a kvel of support in the excavation In ctha headings, whac the ore is d v e, there m y be cancans for proper support if MineguarcP is u d as a rtmdslone 0-e. boltless) systern Using MinegurrdTY and bol& in the massive sulphide hdings wiu.. overcome this concemclcetn The support guidelines assume that then is no delamuiatian occurring 4 t h the rockmass. The quality contrd of the application &If must be assud. This is me for 9 support systerns. These design guidelines assume appropriate qualitty 1- are applied. The design guidelines are bad on limited laboratory testing a d unlaground pafomvn~e data Care must be aacid when applying these guidelines for fùture thin liner support designs. The design guidelha ut basecl on the perfomuuiee and chsraderistics of pdyurethone coatings (MîneguarcP) with specific rssumptions for the *ion ancl temile The recornmendahns cannot be directly applicable to atha produas wnai the straigihc and other physical charaderistics vairy hm those assumed.
306 Whensuppoctdesignisrspuindîorex~1~inaUCllOddbysmicarrdtht~ physical chsractenstia (ad mt hm the inauen# of highbw stress), a guiddint for rlloanbk spans can be estimated- F m the anaiyticai ud unpirial dm tk fbibwiiig maximm spanguidelinesiueprovided, f9rtwovaybroadmdanassqunlitydompinr. For SRF =: 1.O and for permanent = 1.6): 1. ForQ'=O.lto > the liner can be used as screen replacement > the aiiowable span = 1.3 m for boltless > for spans > 1 m, bohs must be used 2. For Q' = 1 to 10 (fàk to gmd rockmass quality): > the liner can be used as screen replacement P the allowable span = 3.2 m for boltless excavations > for spans > 3 m, bolts must be used in the back > for ( 3 c spans c 6 m ) use a centre row of blts in the back > for ( spans > 6 m ) use a systematic bolting patteni 7.83 S~onti.oUcd Fdun- AEowabk Spans Numerical modelling is used to assess whether stressdriven fàilure is likely for a given excavation, The value of ( a,,/ a, ) is used to predia whetfier stressanven fkilure is likely to influence the sbbility ofthe excavation. If stress is a concern for support design, the deph of stress-slabbing and fidure is predicted using the deviator stress crit&on These support guidelines assume support is requïred for permanent = 1-6). 1. For(o,/a. <0.4)strrssisnotaa>nzmfornippaidesigr5thereforethcsbovc design guidelines, buod on rockmass charsderistics, are used.
307 These recommend8u101~ are bmd on some very g d assurnptiow and shouid k used with caution until didateci.
308 The fouowing Table 54 summaka some ofthe hy kncotr of a thin polyrnetbpne sprayon liner: Table 54. Benefits ofa thin rapid-setting sprayon liner Low matmal handling requirements Reducad developmenf cycle time and immedia~e support fw re-eritry Reduced fiction losses Reduced powa a>st for vaitilaîbn (where appropriate applic-ations hpvt ocnirred). Refiective Non orrosive, prothe coating Tmproved visibility Eliminates corrosion of screen and boits + Flexible and able to defom No rehabilitation ofqacked/chipped COlifings Liquid application Support Capacity of 4 tons (for 6 to 8-mm thickness) Lowrebound 1 Able to span joints and coat the rock 1 Elirninate screen and expand bolt paîteliminaîe screerr-and-bolts in Reduces waste and c h p time and Polyurethane spray-on coaîings wen initially designed and introduced îo the hardrock mining industry to be used for ground support via rock stebilization. Howevr, other cmstmdion projects in the underground mines or surface plants may dur ben& fbm the use of rapidlydeployable, fast-setting sprayen materiais.
309 In the realm of ground support, pdyurethuie ünar offa an &ili to sipificantly incrasc productivity with highspeed drieing opaotions. In thu d o, the liner is usai as cornpletc replacement of screm whilc the bits miy be idled off4ine at a lrta date. In fàct, depending on the span of the excavrtion and the danud hm Wichnc ud stress, bits may not be required fa the rie of the excavrtion Acumiing to the rrultr of the support design section of this thesis (chipa 7), a rpui limitation ofapproximately 3 to 4 metm is rc~sonable for stand-atone linor support fbr typid hardmdr conditions at INCO mines. 1t mua be clearly noted, however, that wider spens md/w zrfres~-hcûmd and/ot poor gmund conditions wwld require the immedîate instolhion of bdtr with the liner- A wida bolbig prnan (than that used with screen) could be implemented- For wall support, it is estimatecl that a strong polyur- liner is capabk of replacing both bolts-and-screen for most development and production headings. Only highly stressfiactured gound conditions in the wdls would require additional bohiig with the lina. It is also feasible that short bolts, used in conjunction with the sprayon liner, wdd provide enough beam support for the stability of the excavation for most excavations. Polyurethane liners also offer a potentid to replace shotaete in some operations, as a means of controliing rockmass bulking about mine openinp. Additional testing at INCO has demonstrated the usetùlness of a polyurethane liner to replace shotctete in certain produdion environments (eg. dot and slash) whae repeated blow-back fkom production blasting is not anticipated. Some recent uniaxial tests on coated and uncoated cores and cas& conuete cylinders have demonstrated the ability of polyurethane liners to control the pst-peak failure of the materid [Archibald et. al., Wii this knowledge, the liner offers potential application for stability to rib pillars and pst pillars. In this scenario, the pillar integrity is maintained by limiting spalling of the pillar wails by the confinement off& by the liner. This is analagous to the sbbilizing mechanism wmson & Kazakidis, offered by maintainhg ore passes fil1 of muck in high stress enwonments.
310 Specific underground applications can also be considaed in the uranium mining inbstry, since the sprayed coating is an effdve radon p ôanier. A thin COBting (0.4 mm in thidowss) hr been demonstrateci as king more than 99% effective at shielding radon gas [Archiid et. al., 1997J. The spray-on Liner couid potentially be used as a support product during sinking of a mine SM- The rapid-dg liner then allows for UKxeased sinking rates, since the timecorwming bohing and saeening requirernent wodd be eiiminated or greatly reduced. For the long-term support of the shaft, a concrete Sig is generally required- In der to achieve o &&nt bord between the conaete and the pre-sprayed pdyurethane tining a polyvïnyl acetate coatuig d d be u d to prepare the liner surface (Carey, 1996). This coating d l ensure an adhesive strerigth in the order of 2.76 MPa (400 psi for the concrete to liner intediace. Additional underground mining uses for fastnring spmy-on liners that are king investigated by INCO researchers include some of the following: conveyor belt coating agent - to enhance beit longevity sump liner - to captwe mine wata and make sump cluning easier ventilation tlow barriers - using sprayed geotextile surfaces in place of timber bankades
311 raisebore holes - for mck support in bored raises where res tric ted worker access hinders conventional support instdlation (Le. for ventilation raises or manways), Figure 155. There are cases of rockrnass deterioration in a number of INCO ventilation raises, where no support has been installeci. These failures do not threaîen the stability of the excavation; however, the friction factors would be adversel y affected. Figure 155. Raise bore hole in high-stress mining environment production holes - to line and support ïïh or tophammer holes, to prevent spalling and cmshing of the blasthole walls when mining in broken ground or in high-stress, high- convergence areas ore/waste passes - for support dong the walis of passes in high-stress ground, Figure 156. The abrasion-resistance of polyurethane liners is reportedly very good, but the constant Wear from free-fang muck and the impact from large chunks may make this inappropriate for INCO' s hardrock mines. Figure 156. Stress-convergence in an unsupported ore pass at INCO Figure 157. Post-pillar at INCO's McCreedy East Mine, Main Zone
312 .. temperature mamtad at 1 S.S0C, minimum nitrogen blanket is utiiued fm the Uocyrnste chemicals, to prevent regdion of isocyanates with moishue in the air Prior to each application, it is recomrnended that the chernid raaion be testai, to aiaurr thst material quality will k achievable- Onah samples of liquid shaikl k drawn fhm ea~h d m and Mxed within a separate buckct As soon as the two liquids are paired together, the tester is to agitate the liquids with a stick mixer whib immediaîely starting to time the setup. The following table dehes the Pssociated set-up times with the approwmate d i n of the materials, Table 55. The daion of materid quality is based on experienced applications personnel [Co- person, commun-, Table 55. Set-up times correlateci to material qudity Sct-Up Timc (seconds) 3to5 7to 10 loto 15 > 15 Ma- Excellerit Good Poor Expired Qudity This table obviously requk that sw judgment will nted to k mde on the part of the applications person Fa inswce. for a set-up Eime beyond 7 seconds, new materials mpy be required.
313 the condition of the cxcz1vation surerce (i.e. the h l ofdampness) the intended use of the liner, ud A very wet environment would rsquirr a riq6d-w mitalll. Pmnr qwlity materials wiil likely result in an inefféctive vrsta scavenger be diminished. Specincally, a long shelf-life d l pn4 as a ma&, the lina quaiïty will lkdy m h in the water scavenger behg consurneci during stomge. Thedore, during application, the moirrturr on the rock Sumcc will attack the liner itself since the water mvenger will no longer be presemt in the mix The lack of scavenger chernicals will p~nt the adhesive bond hm ocarrlig between the pdyurethuw liner and the rodç A&r the application, the incffedive lina wiil padually bsanne dctrhcd fkom the rock &. nie properties of the Mineguardrrr polyurrthane liquids and the final cured &g Table 56, with the associated ASTM testing standard: an üsed in Table 56. Properties of Mineguar-: cornponents and aired caating prylon, 02/98] ViçoositY AS-D cps cps Specific Gnwity ASTM D
314 The liquids SM bc thoroughiy mixai prier to eppiicptiois with partinilar cmphsis on the component B, resin, pfoduct Failurt to mix propaiy will yicld a poa qudity coafing. A submersible mixa is used at PICO, wah the mixa bang p W in the dmm for agitation. Ifthe product has been Sitting for extendeci tirne, in the order of weeks to rnonths, the agitator is used for 6 to 8 hours. Ofteri, the mixer is placed in the drum at the end of the aftemmn shift, with mixing overnight, in preparation for spraying the next day shift. Foaming of the coating indicaîes moisture problems that are typically foliowing problems, with suggested remedies: by one of the Moist surface: the ventilation volume and/or rate can be incrcased to allow for ber drying of the rock surface, once it has been washed down. As well, air drying with a blow pipe or similar device will remove obvious puddles on the walls etc. Water in the isocyanate dmm: use of a nitrogen blanket by using a nitrogen cartridge will eliminate the possibility of water fiom the air reacting with the isocyanate material. The use of a nitrogen blanket is recommended once the ISO4mm has ken opened and any liquid remnants will not be used for a while. Very high humidity a dor low temperature: portable heatm and ventilation alterations can aid in reducing the humidity and increasing the air temperature (to prevent dew point fiom being achieved).
315 Alurninum Plate Test: MinegwrP is spraycd onto an binum plate and an immediate response and set-up must occur for 1: 1 mixing Touch Test: an acpaied opana will detm grossly off-ratio k ing by touching the liner immediately der application. A tacky texture indicotes a resikrich liner while a brittle texture indicrites ISO-rich k ing. Colour Test: an ofehtio colour change across the spmyed surface. mix will cause strcaking of the liner, with obvious fingers of Thickness Test: an experienced operator can gauge the rate of application to an estimated thickness of application Remote wntrolled application will also allow for accurate thickness applications. MineguarP is sprayed onto the excavation dace using GracoTM air operated punps. The two chernical components are punped fiom their respecîive 55-gallon (US) drums by air operated Gracmm Monarch dmm pumps to a Gracum Bulldog pçtaging proportidng pump at a one-twne ratio. Electric heaters are used to heat the tesin and isocyanate liquids to 5WC. At this temperature, the two liquids have near-identical viscosities, which is requirrd for the popa mixing. The high pressure pro-staging pump delivers the two oomponents at a pressure of 138 to 172 bar, which ensures adequate mixing of the materials in the mixing chamber ofthe gun. The application equipment for plural componnit sprayon materials is rcddy availabk fbm the polyurethane industry, although the manufkûmm have not fdly eddressad dmstne~ fot underground rnining use yet.
316 The srpicd application equipment consists of the following arrangement: 1) two submersible pumps (one in each dnim), Figure L58, 2) two proportionhg pumps to ensure 1:l voluxne draw of the liquids, 3) dmm heaters to raise the temperature of the liquids to F (50-60 C), 4) a heated hose unit to transport the heateâ Liquids, 5) a short 15-ft. whip hose, and 6) the spray gun. Figure 158. Drums of polyurea chemicals: submersible pumps ùiserted through bung holes The heated hose assemblage contains three internai hoses: one for isocyanate liquid, one for polyol, and a hose for compressed air to operate the hose valves at the gun, Figure 159. For application, the two chemicals are heated to a temperature of 1WF. At this temperature, the two chemicals have virtudy the same viscosity that aliows for complete polymerization and curing of the coating. The mixing of the two chemicals actually occurs at the exit point of the nozzle, with a mixing ratio of 1: 1. Figure 159. Spray gun The curing of the product is practically instantaneous, depending on the thermal characteristics of the substrate that a polyurethane product (like Mineguq is sprayed onto. For instance, application on styrofoam results in immediate curing, while application on rock results in 90% cui-ing over a pend of 10 to 40 seconds. All material properties are achieved within 10 to 15 minutes of spraying.
317 At NO, the fouowing solvaaplchemcals are used to flush a d clan the ippüdon equipment: 0 Cellosolve is ussd to dean the spray gun This pdud is approved for use at INCO both on surîàce and underground. Cellosolve is similar to MEK (methyl ethyl keione) yet MEK has a very strong odour whereas the Cellodve is vinually odourless. As with al1 chemicalg the Ceilosolve product must be Mled with caution and with common sense. DOP is used to flush the heaîed delivery hoses and the punps at the end of the application job. This is a strong dianical that must be used with caution Although DûP is approved for use u n d m only sdl quantities are used in this "closed" environment Nominlly the produd is deiivered in a 55 gallon (US) drum, but the flushing of the hoses g e d y only requks two 5 gallon pails for the cleaning process. The DOP is vay thiclq so th* is not suitable for use with the spray gun cleaning. The products are d l y left in the hoses at the end of an application shift, mth the hose heaters lef3 on. As weü, the pumps are l& in the drums. The only exception to this is Y n the area is very damp. In this case, the nitrogen blanket is injected to the d m prior to rosdhg, while the purnps are cleaned.
318 Fordundagroinda<cintioirs,itbimpoc~~t~ywuhdomithcioclrJliinceMd aliow for sufficient drying thee Wdh adapte ventil.tion rates, a 4 hairtim is usuaily enough tirne to dry the rock sudb. As a rescorch initiation, air bbwing on a khiy blasted round during an underground MmcgumP application at INCO was tested as an ahanative to hi& pressurewaterwadhg. Thiscausedwdueduscinthtkding. Furthermorc,thc~~oRen contain traces of water, end this ~#~llted in poor dcruiing of tht rock As a result of the Ml of ground during the underground trial at McCreedy East Mine, the need for a remot8.1;ontroîied application system became apparent. The initiative for cquipment development was takm by Engincerai Coatings Lirnited, of Cambridge, Ontario, with test collaborations with Tracks-and-Wheels and INCO, Mines Research A spray am was mounted on the rear end of a Kubota-520 forklift trador fiom Tracks and Wheels. This carrier was deemed a good choice since this is a commonly used piece of equipment in the INCO mines. Furthemore, the Kubota is small enough to be cageable (for most N O mines) and it is easy to operate. An auto gun fiom m e r (GX7) was selected for the equipment since this spray-gun has proven success an the robotic cunu in the manuficturing inckry. A speciollydesigned bmckeâ was construded, to mount the GX7 gun on the end of a shotaete boom Once the gun was mounted on the remote am, a newly designed elecüical conad sysiem was hooked up for opaating the gun remotdy from the shotcrete am control panel. The new conîrols were also fitîed with safi featurrs, such as ground hlt intemipters, an emergency stop kmon, and water-tight connectors. The entire mup is easy to assemble and disassemble, for maintenance and repairs.
319 A carry-cage was also desigwd and built, to fit oato the forks of the Kubotaw-520. The equipment for the polyurethane her application is easiiy stored and transported in bucket. Specitically, the cage is large enough to carry and store the pump, the hose, two drums of matenal, and four breathing-air boales. As weli, a smaii tml kit is carried with the unit, for rninor repairs. This entire unit enables quick and complete eransportation of ail the necessary equipment and materials for an application. Afier initial Iab tests by the fabricator, the remote-contml system and spray-arm unit was tested underground at INCO's Research Mhe, the 175 OB [Seitz, This test was compteteci in April 1998, with excelient results. Although the controls require some experience, the application was achieved easity and smoothly, without indications of problems or waste. Some of the testing parameters that were completed include the foilowing: 1. rnaneuverability of the spray ami, 2. total reach of the am, 3. ability to properly apply MineguardTM with the remote-controls, 4. compatibility of the spray-gun controls with the spray-arm controls, and 5. performance of the osciilating head and tilt features on the arm Typical rates of Mineguardm application approximating 2.0 m'/min, ar final layer thickness approximating 1.5-mm, were obsewed. Because such rates were achieved using Figure 160. Remote-controlled shotcrete application equ i pment photo Courtesy of Miller Technologies,
320 Alternative equipment design is unchuay at MEYCO as wdl, with an em~hpsis on sbataetc appiicatjons Bschumi, 199ûI. This is a biuy robaticacd piecc dequiprnent drit win CMpUlly have the capability to acamtdy appiy 8 designaj thidntsr of rhoterric iiptcrpi tû the excavation m ke- This snuipmmt wül dso be capable of applying a thin sp;py-on ha material. Polyurehne materiaiq since thcir Untroduaion in d y varîanî fomi in 1989, continue to be the subject of intense investigation by varbus mine operator gmups. Although origidly developed only to k a replacement for the screen component of boit-and-screen support, this produd has dernonstrateci signifiant potentid benefit in otha mining applications. Based on field and laboratory studies, this material has demonstrated that 5 is capable of achieving a retaining support capacity that lies intermediate beniveen that genewed by sct8enand-bolt and shotcrete support systems. For a variety of reasons, the least of which include the ability to be spray-installed at exceptionally high rates and to cure within seconds der installation, polyurethane materials exhiiit noticeable production and handling advantages over both other forms of traditional area rock support evaluated. During a six-year study intemal at INCO, in which polyurethane liners were shown to be capable of generating significant levels of rock support, these thin liners have also demonstrated other significant mining-related benefits. For instance, by the nature of its colouring spray-on liners are able to generate significant lighting impmvement in underground environments. The capability to mitigate oaen inadquate lighting conditions and worker dety hazards.ssociateâ with these conditions (although mt a primuy design feaîure of these products) mld provide significant potential safi and mat ôenefits to operators in the long terma
321 Physical property evalwtion of the sotid, aôcasiokfesistant polywethaae liner mataial bas also reveafed Minegu~rcP and Rockgmd to be two of the moà &dve sprayable barri- to radon gas diision yct meamrai. In d m mine applications, specincaiiy, or at other mines whert radon moy aie Ma cuatings ofthw mrtaiel have thaoreticaiiy becn shown capable of signifidy rsduung ndoa idowr d p o u worlrer envi.oiimcntrl hputds associated with radon Limited laboratory and field site tests have dso indicaîexi that reduced ventiletion operathg costs may be a ttrii to abation of fncîion fjictor ditions seen to resuh hm polyurethane liner applicaîion onto airway sudkas. Should widespread mine use of this agent eventually develop, it is expected th& reduction in material cost would develop due to ecunomies of scale. in this regard, potential adoption might also be eventuaily contemplaîed by operators who currently view MineguarP's high cost as an impediment for its use as an acid mine drainage barrier agent fbr surficc tailings mitigation In the cases of radon rnitigation and fiction fkctor enhancement, no large+scale field assessrnent trials have yet been conducted to verie promising iaboratory and dl scale insitu test results. This limitation exists, in part, due to the short operating history and limiteci use by the mining industry of the MineguardTM product. With additionai and continued successfiil field testhg by interestecl openitors, such as INCO Limited and Falconbridge Lirnited, adoption of thin spray-on liners may becorne a reality for use in the varieiy of positive findional roles for whkh they have demonstrated. The work describeci in this thesis applies to the irnplementation of spray-on liners in the hardrock mining industry, with a main foais on using liners for gnxuïd support at INCO. W~th regard to polyurethane materialq the technical, operational and practical solutions h m a APcaAt of testing (prirnarily by MIROC and INCO Ltd) have been completely documented.
322 .. ofarocksupport The following Table 57 summarizes the ideai properties and hmckmks produd lespley, Table 57. Idd spny-on liner propertics and chrrcteristics Non-combusli'ble - High tensile sirengdi High achsive stmgth Tough membrane (hardness) Fiame Spread Raîïng, < 200 >SMPa > t MPammcksubsaates Shore 4 Hardness 80 1Wh to 15Wh- High shear strength >lmpa 1 Rapid cure tirne 1 <lhora 1 Able to be sprayed onto humidwet surfaces Rapid application nites Long pot life I Simplistic application I Minimal swface preparatioon I
323 Archiid, J. F. and De Soiaii, E M "Mine Sqqmq Râdi;itim and VedMon Cmtrd wirh Spray- Barries." Symposium 00 High Lcvd Nuclcar Wasic Mamgenmu, Las Vega& Nevada, U.S.A, Apd 26-30, American Nudear Society, La Grange Pa* Illuiois, pp. 177û-1777.
324 Barton N. lm, "A Q-S- Diflicuit Condi- h Rpeoed d Cavcrn Design in Fadial Rd". an T- in Th, My, 16: Carey K ApgiigtKns d~ateskaycradrminc,b.c Pd- * -
327 Hoek E.,Kaisa PX, and Bawden W.F SUppwr of Undergnnuid-n Roctedm HadRaak AA BaILaiq