Metro Montreal Successful operation of a state-of-the-art roadheader ATM 105-ICUTROC competing with drill & blast operation in urban tunnelling

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1 EUROCK 2004 & 53 rd Geomechanics Colloquium. Schubert (ed.) 2004 VGE Metro Montreal Successful operation of a state-of-the-art roadheader ATM 105-ICUTROC competing with drill & blast operation in urban tunnelling Author(s) 1 Uwe Restner, VOEST-ALPINE Bergtechnik GmbH, Alpinestrasse 1, 8740 Zeltweg, Austria Author(s) 2 Bruno Reumueller, VOEST-ALPINE Bergtechnik GmbH, Alpinestrasse 1,8740 Zeltweg, Austria ABSTRACT: The Line 2 of Montreal s Metro system is extended towards Laval connecting a large residential area with downtown Montreal. Tunnels with only little overburden in crystalline limestone, fossiliferous limestone and shaly limestone, intersected by shale layers and diabase dykes cross a very sensitive residential area, have to be connected to already existing underground installations of the metro system and underpass a large river as well as existing tunnels sensitive to vibrations. On demand of the engineering consortium SGTM, VOEST-ALPINE Bergtechnik (VAB) was involved at an early project stage for pre-investigating mechanical excavation. The consulting work included a feasibility study for mechanical excavation using a roadheader of the heavy weight class like the ATM 105-ICUTROC. This early involvement guaranteed a reasonable assessment of operating figures for the roadheader assigned to the excavation work and finally laid the foundations of a successful bid of roadheader against D&B operation. 1 INTRODUCTION The use of a roadheader for hard rock tunnelling applications in North America was not very common in the last years. Thus, VAB was trying to place a state-of-the-art roadheader on the North American market, which should be seen as a reference project to prove the suitability of a roadheader for this field of application. In former years the application of roadheaders had been well accepted to coal and industrial mineral mining, but only few machines had found their way into tunnelling projects, where mainly soft rock had to be cut. The reason for that could be found in the size of the roadheaders, which had been on the market at that time the small sized and light weight machines had been limited to cutting in soft rock conditions. Recent improvements of roadheader technology had opened the door to hard rock tunnelling with heavy weight class roadheaders (>100 tons). Especially the ATM 105-ICUTROC has proven to be a highly versatile excavation machine, capable to operate in hard and even fairly massive rock mass conditions. The main arguments for the use of roadheaders for tunnel excavation are the high flexibility in shape and size of tunnel cross sections as well as the possibility of multiple face and step operation, the quick mobilization of the excavation equipment and the absolutely smooth excavation method with only little over profile and very little impact on the stability of the surrounding rock mass by avoiding any significant vibrations.

2 2 PROJECT DESCRIPTION Montreal s current Metro system consists of four lines and was built in the early seventies. Three years ago the Department of Transportation awarded the design contract for extending the current Line 2 from Henri-Bourassa-Station to Laval. The extension of Line 2 connects a large residential area with downtown Montreal. The detailed project engineering as well as the supervision of the ongoing construction work was awarded to the engineering and consulting consortium SGTM. The engineering work started in early 2001 and the construction finally began in July The schedule calls for completing the excavation by July 2004, connecting up to the already existing Henri-Bourassa-Station. The new metro extension has been budgeted at 380 million Canadian dollars and will be commissioned in January Site description and project details The extension of Line 2 consists of various challenging projects. Some tunnels cross very sensitive areas with little overburden and residential buildings. These tunnels have to be connected to already existing underground installations of the current metro system. One tunnel even has to under pass a large river as well as tunnels sensitive to vibrations. The project has a total length of 5.2km and comprises single and double line tunnels, stations and auxiliary structures like shafts and ramps. These constructions have to be carried out either by roadheader or by D&B. The most critical part of the project is a double line tunnel of 600m under passing the river Rivière des Prairies with an intersection to a single line tunnel. In the intersection area the tunnel has a maximum width of over 16m with a minimum rock cover of 9m equalling the distance between the roof of the tunnel and the river bed. Figure 1. Site map of Metro Montreal Line 2 Extension and detailed map of Lot C04 As shown in Figure 1 the excavation of the main tunnels has been divided into 3 lots C01, C04 and C05. The Lots C04 and C05 were projected for either D&B or for roadheader excavation as alternative method. But for C01 there had been some serious concerns about the qualified excavation method. The designers and engineers were concerned about the very thin cover of 9m between the top of the tunnel and the river bed. In case of developing cracks and fractures caused by blasting, the water comes straight into the tunnel and endangers the whole project. Hence a strong emphasis has been placed on roadheader excavation, ruling out D&B.

3 2.2 Geologic description and geotechnical details Montreal is located in Québec, an eastern province of Canada. Almost 90% of Québec s bedrock consists of Precambrian rocks of the Canadian Shield, north of the St. Lawrence River. South of the river, the bedrock is mainly composed of Paleozoic rocks forming the St. Lawrence Lowlands and the Appalachians. The project area is situated in the St. Lawrence Lowlands (age: Ma) and comprises a sequence of shaly, fossiliferous and crystalline limestone with shale interbedding, sub-horizontally bedded, and diabase intersections, vertically oriented. Figure 2. Mechanical rock data according to drill core samples During the pre-investigations VAB was invited by SGTM to visit the site and evaluate the drill cores. The objective was to collect as many information as possible required for rock mass cuttability assessment. Thus, special attention was given to evaluation of rock mass structure. Many data was obtained from drill cores, but highly valuable information could be gathered also in a quarry in Laval, where a large part of Laval s geology is exposed. In this way it was possible to get a very clear and detailed picture of the project area. Further on, some representative rock samples were taken to be tested at VAB rock lab to receive some figures for rock mass cuttability assessment. The figures for net cutting rate and specific pick consumption finally had to be guaranteed to the potential contractors working with the roadheader. Overall UCS has been determined with ~90MPa, resulting in a net cutting rate of 27 solid m 3 /h for intact rock. For the evaluation of rock mass features affecting net cutting rate VAB uses a revised RMR system, called RMR rev, and equation (1) to correct the net cutting rate for intact rock NCR theor and calculate the effective net cutting rate NCR eff considering rock mass conditions. NCR NCR eff = RMRrev theor According to a RMR rev value of ~30 a effective net cutting rate of 44 solid m 3 /h was calculated. Considering a certain risk VAB was prepared to guarantee an effective net cutting rate in the range of 38 to 42 solid m 3 /h and a specific pick consumption of 0.1 pick/solid m 3. Based on the operating figures provided by VAB, Neilson had prepared their bid based on using the ATM 105-IC for the tunnel excavation and turned out to be the lowest bidder compared to other contractors using D&B for the excavation work. (1)

4 3 MACHINE OPERATION The ATM 105-IC started operation at Lot C04 in October First a ramp was cut down to tunnel level and then the machine worked at two faces in the main tunnel. Neilson made a shift setup with two 10 hours cutting shifts and one back shift for rock support installation. The 4 hours idle time was used for maintenance and place change. Average NCR: 39,19 solid m 3 /h Average SPC: 0,103 picks/solid m 3 Operational Daily Data of ATM 105/028-IC at Montreal/Canada Net Cutting Rate (NCR) and Specific Pick Consumption (SPC) Net Cutting Rate [solid m 3 /h] Date 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 Specific Pick Consumption [picks/solid m 3 ] Daily NCR Cumulative Average NCR Daily SPC Cumulative Average SPC Figure 3. Recorded ATM 105-IC operating data at C04 For operation monitoring VAB created a reporting system combined with a complete statistic analysis for operating data. Additionally, some site visits were made to compare recorded operating data with encountered geology and rock mass conditions. Figure 3 gives an overall view of machine operation at Lot C04. Obviously, the obtained operating data net cutting rate and specific pick consumption are in the range of the prediction. Nevertheless, the contractor Neilson pushed the machine very hard to keep the schedule. There were some discussions between VAB and Neilson over the term effective net cutting rate and cutting rate. VAB defines the net cutting rate as follows: The volume of cut rock per effective cutting time defines the net cutting rate. The effective cutting time is defined by the time the cutter head is in contact with the rock and actually cutting. Thus, supplementary profiling or loading time does not count to the effective net cutting time. The objective of Neilson was to cut 10m of tunnel per day. Considering an average tunnel cross section of 44m 2 and the assessed average net cutting rate of 40 solid m 3 /h, realistically 8-9m per day could be achieved in a 3 shifts operation, assuming 90% machine availability and 50% machine utilisation corresponding to 30% effective net cutting time, which are typical average values as past tunnelling operations have shown. The effective operating data gathered by Neilson is listed as follows: Shifts per day: 2 cutting shifts (1 shift for rock support installation, not recorded) Average cutting shift time: 9 hours Machine availability: 97% Machine utilization: 90% Effective net cutting time: 49% of shift time

5 Average daily advance rate: 8.6m Average net cutting rate: 39 solid m 3 /h Average specific pick consumption: 0.1 pick/solid m 3 Total excavated volume: 70,570 solid m 3 Although it was their first tunnelling job with a roadheader for the excavation work, Neilson did an excellent job and learned a lot for future roadheader operations, especially with regard to the probable contract for Lot C01. Figure 4 shows the operational details of the job at Lot C04. Operational Data of ATM 105/028-IC at Montreal/Canada Machine Utilization and Standstill Times according to Total Shift Time 3% 4% 1% 1% 1% 90% 49% 73% Total Time of Machine Utilization Total Cutter Motor Hours Total Net Cutting Hours Total Time for Pick Exchange Total Time for Maintenance Total Time for Lunch/Travelling Total Time for Standstill-Machine Total Time for Standstill-Job Site Figure 4. Statistic analysis of operating data at C04 The downtime for the job site 4% of total shift time was exceptionally low, which indicates a very good infrastructure and organisation of the job site. The machine utilization of 90% is quite impressive, but it has to be mentioned that this percentage is based on the hydraulic hours of the machine and consequently also includes the tramming time from one face to the other. Also the job site staff was very lean. For the operation of the roadheader 2 men are required, 1 for operating the machine and 1 for assisting the operator. For the complete operation there were 30 people on site, including 5 people for job site administration. 4 MAIN ADVANTAGES OF ROADHEADER EXCAVATION Although Neilson had some concerns about meeting their target figures, finally the roadheader operation proved to be the right choice. The schedule as well as the costs for the excavation were met and when the final lining was installed the real benefits of mechanical excavation came to light. 1. No problems meeting vibration limits. Absence of complaints or litigation from the local residents. 135 complaints issued on the D&B tunnel section. 2. No stability problems according to smooth mechanical rock mass excavation. No activation of joints and fractures due to absence of blasting shock. 3. Average over break or over cut respectively of 8cm cm reported on the D&B tunnel section. This resulted in significant savings on installation costs for final lining! 4. Higher advance rate based on a single face operation. The very accurate profile of the cut tunnel turned out to be beneficial to the installation of the final lining. The cost savings in concrete and working time have shown a tremendous effect on the entire tunnelling project. On the total length of Lot C04 of 1200m the savings in concrete compared to the D&B tunnel section were calculated with 4,960m 3 or 1,785,600 Canadian dollars (360

6 Canadian dollars per m 3 put in place) not counting any time loss. Moreover, no additional low strength floor concrete had to be placed for the D&B tunnel section up to 1m 3 of low strength floor concrete was required. Also the additional grouting work in the D&B tunnel section took more than 1 month for 2400 tunnel meters in the roadheader tunnel section the grouting work for 1200m was done in 3 days. Figure 5. Profile of cut tunnel (left side) and blasted tunnel (right side) 5 CONCLUSION All in all the mechanical excavation at Lot C04 turned out as an outstanding success. The operation showed that a roadheader can not only compete with D&B in urban tunnelling projects, but is definitely advantageous for certain project criteria such as restrictions in vibrations, excavation profile accuracy, avoiding stability problems, etc. Finally, the success of the use of the ATM 105- IC roadheader for the tunnel excavation at Lot C04 caused the contractors Neilson and EBC, which had used D&B at Lot C05, to form a joint venture and to become the lowest bidder to win the bid for the Lot C01, which had been tendered out for mechanical excavation. Specifying the method of excavation in the tender documents is not a normal practice in North American tunnelling, but with the experience gained in Lot C04 using mechanical excavation in comparison with Lot C05 using conventional D&B, the project owner specified mechanical excavation for Lot C01 to reduce or even avoid potential problems. ACKNOWLEDGEMENT The authors acknowledge the important contribution by Neilson excavation, SGTM and the owner in supporting the introduction of the ICUTROC ATM 105-IC in North America. Special thanks are also due for permission to disclose the operational results. REFERENCES Gehring, K.H. & Reumüller, B Hard rock cutting with roadheaders the ICUTROC approach. In R. Hammah, W. Bawden, J. Curran & M. Telesnicki (ed.), Mining and Tunnelling Innovation and Opportunity, Proc. NARMS-TAC 2002: Toronto: University of Toronto Press. Restner, U. & Gehring, K.H Quantification of rock mass influence on cuttability with roadheaders. In Proc. TUR 2002: Kraków-Krynica: University of Mining and Metallurgy. Rodney, G Montreal breaks new ground with roadheader. World Tunnelling October 2003: