Keywords: lime treatment, reuse of local soils, internal erosion, overflow, durability, dike design

Transcription

1 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction Rostock, April 2014 ISBN: LIME TREATED SOIL AS AN EROSION-RESISTANT MATERIAL FOR HYDRAULIC EARTHEN STRUCTURES: STATE OF THE ART AND PRESENTATION OF THE FRENCH DIGUE.ELITE PROJECT Gontrn Herrier 1, Pscl Leconte 2, Nicols Nerincx 3, Stéphne Bonelli 4, Fbienne Mercier 5, Fry, Jen-Jcques 6, Tchker, Pierre 7, Puitti, Dniel 8 1 Lhoist Recherche et Développement, 31 Rue de l Industrie, B 1400 Nivelles; gontrn.herrier@lhoist.com 2 Lhoist Frnce, 168 Rue de Rivoli, F Pris; pscl.leconte@lhoist.com 3 ISL Ingénierie, 29 rue Murice Flndin, F Lyon; nerincx@isl.fr 4,5 Irste, 3275 Route de Céznne CS 40061, F Aix-en-Provence Cedex 5; stephne.bonelli@irste.fr, fbienne.mercier@irste.fr 6,7 Electricité de Frnce, Centre d Ingéniérie Hydrulique, F Le Bourget du Lc; pierre.tchker@edf.fr 8 DPST Consulting, 6 rue Adèle, F Villemomble; dniel.puitti@dpst-consulting.eu Abstrct. The tretment of silty nd clyey soils with lime (clcium oxide or hydroxide) is technique widely used for soils improvement nd stbiliztion for construction of rods, highwys, rilwys, pltforms. However, the principles of lime tretment for hydrulic erthen structures remins brely pplied or even forgotten (Europen cse). If existing testimonils (levees, dms, minly in US nd Austrli) re evidences tht show effectiveness nd durbility of lime-treted structures, there ws necessity to evlute series of unknown chrcteristics nd relevnt properties of lime-treted soils for n ppliction in hydrulic context, through lbortory studies nd full-scle experiments. Keywords: lime tretment, reuse of locl soils, internl erosion, overflow, durbility, dike design 1. Introduction Lime tretment of soils is well-know nd widely pplied technique for soil improvement nd stbiliztion of infrstructure works (rods, highwys, irfields, rilrod beds) (Little, 1995). The use of lime treted soils in hydrulic context is less known, t lest in Europe, nd existing structures showing the relevnce of this ppliction re quite rre. However, severl benefits of lime tretment for hydrulic structures construction or restortion were reported in the pst (Gutschick, 1978): preventing softening while underwter (the lime-treted soil doesn t revert to mud), preventing the lekge nd resisting erosion from flowing wter, reduction of shrinkge nd swelling movements of high plsticity index soils (hevy clys). Testimonils of the ppliction of this technique cn be found in some plces cross United Sttes nd Austrli, coming from severl Americn nd Austrlin uthorities nd offices for hydrulic erthworks restortions or reinforcement since the 1970 s (Perry, 1977; ANCOLD, 1978; Gutschick, 1978; Gutschick, 1985; Knodel, 1987; Fleming, 1992; USBR, 1998; Stpledon, 2005; USACE, 2010). In 2005, the Lhoist Group, lime producer, lunched series of importnt reserch progrms to identify the conditions nd procedures for lime tretment nd plcement of soils in hydrulic erthworks. The reserch lso sought to estblish the relevnt properties of mterils for their use in erthen structures in contct with wter. Following this series of relevnt cquired dt, the next step ws to build n experimentl full-scle structure build using the specified methodology nd technology tht hd to show on lime-treted silty soil structure: - the fesibility of the specific lime tretment nd plcement procedures t n industril scle, using dedicted mobile tretment plnt nd conventionl erthworks equipment; - the correltions between the lbortory observtions on lime-treted soil properties nd the rel scle The Authors, Published by Universität Rostock Selection nd peer-review under responsibility of Universität Rostock / scientific committee of the conference

2 76 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction - the benefits of lime tretment in terms of mechnicl improvement nd hydrulic behviour over time, compred to nturl (untreted) soil. Recently nd from these chievements, n mbitious French project clled DigueELite ws lunched in June 2013, in order to estblish innovtions in the subject of flood protection levees. 2. Relevnt properties of lime-treted soils: lbortory reserch progrms 2.1 Mterils The limes used for soil tretment studies were Lhoist Provicl DD clcic quicklime CL-90 Q (ccording to Europen Stndrd EN 459-1), with n vilble CO content of 90.9 %, nd t60 (rectivity) of 3.3 minutes, nd hydrted lime (CL-90 S). Six different fine soils with different Plsticity Indexes (PI), from silty (PI=8) to clyey (PI=37) hve been used to perform the following tests: permebility, isotropic compression, oedometric compression, shrinkge-swell, crumb test, hole erosion test nd MoJET (Mobile Jet) test. 2.2 Permebility The construction of hydrulic structure involves the control of its wter permebility, tht hs to be the lowest possible to limit the wter ingress through the bottom nd the slopes. In the literture, few studies were concerned by permebility of lime-treted soils, nd led to contrdictory results. Moreover, preconceived ide is tht permebility increses fter lime tretment, due to the decrese of soil dry density. IFSTTAR (former LCPC) relized n experimentl study on the influence of the procedure of lime tretment nd compction of silty soil on its permebility. This silty soil, coming from Moulin de Lffux, Aisne deprtment (Frnce), hd the following chrcteristics: cly frction (<2 µm) = 23% ; silt frction (between 2 nd 50 µm) = 59 % ; 88% prticles <80 µm, PI=12.7, w OMC =15.8%, d= 1.81g/cm³. Two different moisture contents hve been pplied t compction: the first round the wter content t the mximl density of Stndrd Proctor test (w OMC ), nd the second, humid stte equivlent to 1.2 times bove this vlue (w h ). Untreted mteril, 2 nd 3% quicklime-treted, nd 2.65% hydrted lime-treted mterils were compcted ccording two procedures: - clssicl Stndrd Proctor dynmic compction, to 95% of the mximl dry density t OMC; - kneding compction, performed with specific tool which simultes the ction of sheepfoot roller (Fig. 1) Koussi, This tool llows respecting the following geometricl nd surfce chrcteristics given by kneding compction roller Cterpillr 825C: - the surfce rtio between wheel nd the compcted surfce (rtio = 3.7) - rtio between the thickness of compcted lyer nd the foot height (rtio = 1.5). The specimens were compcted to the sme finl density s tht of the Stndrd Proctor method. In the cse of untreted silt, this lst compction procedure led to similr optiml vlues ( d nd w), but for limetreted mterils, the kneding led to higher optiml wter contents. The permebility tests were performed t LRPC Angers (Frnce), ccording to the XP CEN ISO/TS Stndrd. The smples were directly compcted in the permemeters (Fig. 1b). When the kneding compction ws pplied, the specific tool ws pushed 8 times with pressure equl to 1.25 MP on the soil, with gyrtory movement. The specimen ws obtined fter the compction of 3 lyers of round 4 cm thickness ech. The permemeter set-up ws similr to CBR moulds except tht they were equipped with inox grids nd pierced pltes for the wter entrnce nd exit. The permebility mesurements were performed fter 28 dys curing t constnt wter content (fter compction), fter 28 dys curing + 2 months immersion period, nd 28 dys curing + 5 months immersion; in other words 3 months nd 6 months fter preprtion, respectively. The following results were highlighted: - kneding compction led to the lowest permebility vlues (k) for given mixture; - for given mteril with fixed compction procedure, the humid stte gve lowest k vlues; - the k vlues of lime-treted soils, Proctorcompcted in the humid stte, ws m/s; - kneding compction of lime-treted soils t high moisture content (humid stte) led to k vlues below m/s, even below m/s. The k vlues remined constnt with time, whtever the hydrulic loding ppliction (constnt or vrible loding). This indictes tht the finl permebility ws lredy obtined fter 1 month (curing done with constnt wter content). As result, the preferred conditions for reching low permebility vlues of the lime-treted silty soil (2 to 3% lime) re: (i) high moisture content nd (ii) kneding compction. These results were further explined by mercury intrusion porosimetry which highlighted the chnges in the porl structure of treted soils (Fig. 2). The biggest pores (>3µm), nd intermedite-sized (between 3000 Å nd 3µm) re considered s responsible for the wter pth. When Fig 1. Kneding compction tool () nd permemeter (b) b

3 G. Herrier et l. Lime treted soil s n erosion resistnt mteril for hydrulic erthen structures 77 dv/dlogd (ml/g) untreted, wopn, Proctor compction 2% lime, wh, kneding 0 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 Pore dimeter (Angstrom) Fig 2. Mercury intrusion porosimetry of untreted (red curve) nd lime-treted (blue curve) smples, s function of wter content nd compction procedure (silty soil from Moulin de Lffux, Frnce, PI=12.7) Volume strin [-] (%) Untreted % lime-treted - 6 months curing Stress p' (kp) Fig 3. Isotropic compression of untreted nd lime-treted silty soil from Moulin de Lffux, PI=12.7 (6 month curing). treted with lime, third clss of smller pore ppered (<3000 Å). After lime-tretment in the humid stte nd kneding compction, the mount of pores > 3µm ws strongly reduced in fvour of the smllest pore size (Figure 2, blue curve), tht do not ffect the permebility. As conclusion, the plcement method of lime-treted mterils is fr more importnt thn finl density in the control of permebility (Cuisinier, 2011). 2.3 Mechnicl behviour of lime-treted soil Compressibility Isotropic compression tests were performed on the sme silt s the one used for permebility (Fig. 3). The volume strin of the untreted smple is function of the logrithm of isotropic stress (log p ), which mens tht the yield strength is below the smllest pplied stress. Once treted with 2% lime nd fter 6 months, 2 slopes cn be distinguished on the grph, seprted by the yield strength between 400 nd 500 kp. Oedometer tests were lso performed t Université Libre de Bruxelles (ULB) on clyey soil from Héricourt (Hute-Sône, Frnce), untreted nd 72 hours fter 5% quicklime tretment (dosge corresponding to the lime fixtion point). This soil hd the p s following chrcteristics: 94% prticles <80µm, 75% <2µm, w P =35%, w L =72%, PI=37, d= 1.45g/cm³ t w OMC =27.5%. Severl observtions were mde: the swelling index ws divided by 5 to 10 times fter tretment (C s between nd 0.010), the yield resistnce (p s ) ws lso multiplied by fctor 5 to 10 (p s vlues between 490 nd 660 kp for the treted specimen). The compressibility indexes were similr for the two series Sher resistnce The im of the sher resistnce mesurements is to quntify the improvement of mechnicl stbility of embnkments brought by lime tretment. The results were obtined t ULB, on two silty soils from Belgium (Soumgne soil, PI=16 nd Mrche-les-Dmes soil, PI=11), treted with 3% quicklime (Verbrugge, 2011). Consolidted undrined trixil tests were performed on smples of 3.6 cm dimeter nd 7.2 cm height, beforehnd sturted. The untreted first silt (Soumgne soil) prmeters re c = 5.8 kp nd = The friction ngle stys stble fter lime tretment, wheres the cohesion rises significntly: fter 2 yers, the c vlue is multiplied by 25. Similr results were obtined with the silt from Mrche-les-Dmes (PI=11), which shows c vlue equl to 500 kp t 450 dys fter tretment. The rnge of mesured cohesion vlues ws well bove common stresses met on smll hydrulic structures Interprettion of mechnicl tests The lime-treted soil cn be considered s cemented mteril, in this sense tht the prticles ssembly is relized by the cohesive bonds induced by the lime ction. This new ssembly hs lso new stress resistnce threshold; bove this vlue, the ssembly is destroyed nd the behvior of the mteril becomes similr to n untreted soil. For isotropic nd oedometric compressive tests, this threshold is not considered s preconsolidtion stress, but more s the yield strength of the new lime-treted mteril of low ductility, quntifying the resistnce of the dhesive bounds creted by the lime tretment. The rise in cohesion is lso due to the so-clled pozzolnic rections between lime, dissolved silic nd lumin species from clys nd wter, giving mteril tht is lmost not compressible, nd not subjected to deformtions if submitted to stresses until severl hundred kp. 2.4 Wter sensitivity nd erosion resistnce Dispersivity, swelling nd shrinkge The ASTM D Stndrd ( crumb-test ) ws used to demonstrte the non-dispersive behviour of n initilly dispersive silty soil from Mrche-les-Dmes (94% prticles <80µm, PI=11), treted with 2 to 3% quicklime. This improvement ws still visible 3 yers

4 78 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction Fig. 4. Enhnced crumb-test performed on the silty soil from Héricourt (PI=11), untreted (bove, scle in minutes), nd treted with 2% lime (below, scle in hours). V/V0 untreted 5% lime the Héricourt clyey soil showed tht, fter 5% quicklime tretment, liner swelling of soked CBR smples remined low nd limited fter the soking step. In the mentime, the bering cpcity reched vlue of 19, to be compred to the very low vlue of 1.3 obtined for the untreted smple. Free shrinkge evlution ws lso performed on this clyey soil ccording the Germn Stndrd DIN The principle consists in prepring disc of soil (dimeter 7cm, height 1cm) t very high wter content (110 %), nd mesuring its dimeter vs wter content when left to dry t room temperture. The shrinkge limit w s is the inflexion point of the two tngents to the volume vrition curve (Fig. 5). At this wter content, the shrinkge of the smple reches the mximum mplitude; below w s, no volume vrition is recorded. In other words, shrinkge/swelling risk exists for soil if its wter content is bove w s. Once gin, nturl Héricourt clyey soil ws tested nd showed w s of 16,5%, linked with big volume vrition (more thn 50% shrinkge). Once treted with 5% quicklime, w s is displced towrds higher wter content (w s =55%), well bove the OMC conditions, ensuring the volume stbility of the mteril Erosion resistnce Wter content (%) Fig 5. Free shrinkge curves of Héricourt clyey soil (PI=37) Erosion rte dr/dt (cm/min) untreted Tngentil stress (P) 2% lime 3 dys curing 7 dys curing 14 dys curing Fig 6. Hole Erosion Test: erosion rte vs tngentil stress for untreted nd 2% lime-treted clyey silt from Cmrgue dike (PI= 11). fter tretment. An enhnced crumb-test ws lso performed by IFSTTAR (Frnce) Chevlier, 2011; Phm, A thin wll smpler ws used to cut out specimens from moulded cylinders (Héricourt silty soil, 67% prticles <80µm, PI=11 untreted nd treted with 2% lime). The untreted cylinder collpsed fter 15 minutes immersion, wheres no degrdtion occurs on the lime-treted smple, even fter 45 hours immersion (Fig. 4). The consistency chnges of clyey soils with moisture content re mterilized by lrge volume chnges (swelling nd shrinkge). Lbortory tests on Both internl (by Hole Erosion Test HET) nd externl (by Mobile Jets Erosion Test, MoJET) erosion resistnce were studied, in order to evlute the impct of lime tretment on the criticl prmeters of the mterils. HET ws performed t Irste (Frnce) on clyey silt tken from Cmrgue Dike (Frnce): 95% prticles <80µm, 30% <2µm, PI=11. After lime tretment nd 14 dys curing, the criticl stress ws incresed by fctor 20, nd the erosion coefficient divided by 10. The device didn t llow the erosion initition of the 28 dys cured smples. HET results cn be used to estimte the threshold wter velocity tht induces erosion (Fig. 6). For untreted clyey silt, the erosion threshold corresponds to wter velocity of 2 m/s, wheres for lime-treted mteril, the vlue rises up to 10 m/s. These results re importnt elements for the problemtic of internl erosion, min origin of hydrulic erthworks filures (Benhmed, 2011; Bonelli, 2011). Additionl informtions cn be found in (Bonelli, 2013; Herrier 2013). The surfce erosion ws lso tested by the men of MoJET test, performed t IFSTTAR. The procedure consists to spry 6 rotting wter jets perpendiculr to smple surfce, with wter flow of 600 ml/min, to recover the eroded prticles nd weight their dry mss. On smple of Héricourt silty soil (67% prticles <80µm, PI=11) treted with 2% lime nd cured 90 dys, the erosion could not be initited, even with n increse of wter flow to 2 l/min, when the sme conditions gve 500 g of dry prticles eroded from the untreted soil.

5 G. Herrier et l. Lime treted soil s n erosion resistnt mteril for hydrulic erthen structures 79 Tble 1. Identifiction chrcteristics of the silty soil from Mrche-les-Dmes (Belgium) Cly frction (<2 µm) (%) 12 Silt frction (2 to 50 µm) (%) 82 Pssing through 80 µm sieve (%) 99.5 Methylene Blue Vlue (g/100 g) 2.50 Plsticity index (%) 7 to 8 Moisture content t smpling (%) 17.9 Dry density (kn/m³) Untreted 2.5% lime Sr = 100% 3. An experimentl full scle hydrulic erthen structure in lime-treted soil Following the series of relevnt cquired dt, the next step ws to build n experimentl full-scle structure with three importnt objectives: (1) proving the fesibility of the specific lime tretment nd plcement procedures t n industril scle, using dedicted mobile tretment plnt nd conventionl erthworks equipment; (2) correlting the lbortory observtions on limetreted soil properties t rel scle (3) evluting the benefits of lime tretment in terms of mechnicl improvement nd hydrulic behvior over time, compred to nturl (untreted) soil. 3.1 Chosen soil nd its chrcteristics A silty soil with low plsticity index ws used for the construction of the experimentl dry dikes. This soil ws imported from Mrche-les-Dmes (Belgium). Its min chrcteristics re reported in Tble 1. A crumb-test, performed ccording ASTM D stndrd on compcted smple of this soil, showed qulittively its dispersive chrcter, priori unsuitble for use in hydrulic context. A dispersive soil is defined s one tht will esily nd quickly disperse (deflocculte) in wter, with no mechnicl intervention. Such mterils generlly hve tendency to shrink-expnd, hve little resistnce to erosion nd low permebility if they remin in this condition. Besides improving immedite workbility, fcilitting plcement nd enhncing mechnicl properties in the medium term, lime tretment is known to control the soil prticle dispersion, due to the ctionic exchnge nd floccultion/gglomertion effects (Knodel, 1987; Fleming, 1992). 3.2 preliminry lime tretment studies The lime used for the soil tretment tests is CL 90-Q quick lime ccording EN stndrd,, contining 90.9% of vilble CO nd rectivity (t 60 ) of 3.3 minutes, supplied by Lhoist. The lime fixtion point of the soil, determined ccording the Edes nd Grim test (ASTM D ), ws between 1.5 nd 2%. A lightly higher dosge of 2.5 % ws selected to ensure the development of middle to long-term mechnicl resistnce Wter content (%) Fig 7. Stndrd Proctor compction curves of untreted nd 2.5 % Provicl DD-treted soil from Mrche-les-Dmes (Belgium). The chnges induced by the lime tretment on the compction behvior of the soil re illustrted in Fig. 7. The optiml moisture content for Stndrd Proctor compction of untreted soil is d =18.2 kn/m³ t w OMC =14.5 %. It is known tht lime tretment leds to displcement of the w OMC towrds higher moisture contents nd reduction of the mximl dry density: the specific compction chrcteristics of the Mrche-les- Dmes silty soil treted with 2.5 % quicklime re d =17.3 kn/m³ t w OMC =17.8 %. 3.3 Mixing nd compction opertions nd equipment The wter permebility of hydrulic erth structure must be mnged during construction. Permebility must be sufficiently low to minimise wter loss through the bottom nd sides. The results from the Sotredi reserch progrm of the Lhoist Group (Herrier, 2012) showed tht under specific tretment nd plcement conditions the permebility coefficient reched on silty soil treted with 2 to 3 % quicklime ws in the rnge of m/s to m/s nd remined stble over time (Herrier, 2013). For the construction of the experimentl full-scle embnkment, the most beneficil plcement conditions nd processes producing the lowest permebility of lime-treted compcted mterils were determined s follows: - fter lime nd soil mixing, the finl mterils must be humid, e.g. wet of optimum conditions. In the cse of Mrche-les-Dmes soil tht mens tht wter must be dded to obtin finl moisture content bove 18 %, once treted. - the compction must be performed with kneding opertions (sheepfoot roller). The objective in terms of density level is to rech t lest 95 % of the mximl dry density (17.3 kn/m³). The equipment used for lime tretment ws mobile soil mixing plnt (Fig. 8), ble to precisely control the lime dosge through continuous weighing of soil pssing through the bnd, nd offers regulr ddition of wter directly in the mixing bell. The prti-

6 80 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction cle size of the treted soil is very fine nd rnges between 0 nd 20 mm. The compction equipment is VP5 sheepfoot roller, ccording the French Stndrd NF P (Fig. 8b). 3.4 Experimentl dikes conception Dike built with lime-treted silty soil The biggest of the two experimentl dikes ws entirely built with the 2.5 % lime-treted silty soil from Mrcheles-Dmes (Belgium). For this purpose, pproximtely 1000 tons of soil were brought to the site of CER (Experimenttion nd Reserch Center), close from Rouen (Frnce). The dimensions of the embnkment re 28.2 m long nd 10.3 m wide t the bottom, 21 m long nd 4 m wide t the crest (Fig. 9 nd b, upper nd longitudinl views). The finl height of the structure is 1.8 m, with different slopes on ech longitudinl side, 3:2 nd 2:1 (horizontl:verticl) respectively, obtined by cutting compcted bnds. The dike is virtully divided into 3 sections of 5 m long, corresponding to the 3 successive mesurements periods of 28 dys, 180 dys nd 1 yer (Fig. 9). The ccess rmps were built with nother silty soil, in order to sve the first one for the bulk of the dike, wheres trnsition bnd of 3 m lime-treted soil ws dded to ensure the constnt speed of the compctor on the 3 mesurements zones. The 2.5% lime tretment with controlled wter ddition in the mobile mixing plnt, produced grnulr, fine mteril t humidity level bove OMC. This mteril ws trnsported directly to the jobsite, nd then tken by shovel for the plcement of 50 cm thick lyers prior to compction. The compction step ws performed with kneding compctor in 6 psses t speed of 3 km/h, producing finl thickness of 30 cm for ech lyer. Finlly, the embnkment ws constructed in 6 lyers, giving totl height of 1.80 m (Fig. 9b). Pictures of ech step cn be viewed in Fig. 8. The top of the dike is divided in 2 prts longitudinlly, one side is reserved for mesurements of plcement nd mechnicl properties such s density, wter content, bering cpcity, pressuremeter, collection of smples b Fig 9. Top view () nd longitudinl section (b) of the limetreted silty soil experimentl dike. b c Fig. 8. Lime-treted mteril production (), ppliction nd compction with sheepfoot roller (b), globl view of the lime-treted dike (c) nd of the two dikes (lime-treted nd untreted, on the right) (d). d

7 G. Herrier et l. Lime treted soil s n erosion resistnt mteril for hydrulic erthen structures 81 for trixil testing, nd hole erosion testing. The other side is reserved for permebility mesurements. In situ surfce erosion mesurements will be performed on the slopes Dike built with nturl (untreted) silty soil The second smller embnkment ws built using the sme initil silty soil, but without lime tretment. The structure consists of 3 lyers with compcted height of 30 cm. The totl length nd width t the bottom re 13.6 m nd 5.6 m respectively. The crest is 10 m long nd 2 m wide. The slopes hve 2:1 vlue. The mteril ws plced t the sme humid stte s the lime-treted dike nd ws compcted using the sme kneding equipment. The compction level ws 95 % of the mximum dry density t the nturl stte (1.82 g/cm³ ccording Stndrd Proctor compction). A single mesurement section is foreseen, becuse the mteril properties cn be considered unchnged over time. The sme mesurements were foreseen s for lime-treted sections. 3.5 Results Efficiency of mixing nd plcement procedures Dike built with lime-treted soil The tretment nd plcement objectives were to produce 2.5% lime-treted mteril, with moisture content bove OMC of the Stndrd Proctor; to compct this mteril by kneding, nd chieve compction level t lest equl to 95 % of the Stndrd Proctor density t OMC. Tble 2 presents the mesured vlues of wter content, lime ddition, nd compction level, on severl lyers during the plcement, long with the top lyer fter the leveling opertion. The mesured lime nd wter contents nd the clculted stndrd devitions of the mixture composition show the high level of homogeneity of the treted soil, nd therefore the consistency of the production using the mobile plnt. The objectives in terms of wter content > OMC, trfficbility nd density level re reched. This lst vlue exceeds on every lyer the 95 % of mximl dry density mesured ccording the Stndrd Proctor test. Tble 2. Mesurements performed on the lime-treted dike fter plcement Lime Wter content density level dosge (%) (% (%) d t OMC) bove OMC objective 2.5 equl or bove 95% (>17.8%) verge 19.4 (w-w OMC = 1.6 %) 2.5 mesurements stndrd devition (lyers 2-4-6) 98.5 (top lyer, leveled) 18 (lyers 2-4-6) 24 (top lyer, leveled) 1.1 (lyers 2-4-6) 1.1 (top lyer, leveled) The issue of homogeneity for treted soil is lwys rised when discussing this tretment for hydrulic structures, becuse tht prmeter is closely relted to the permebility grdient. The issue is crucil becuse n unforeseen permebility grdient my result in bnorml nd loclised flows. It seems tht this objection is rection from geotechnicins, nd tht the suspicion hs two probble origins. On the one hnd, it is lwys very difficult to obtin homogeneous soil in civil engineering, notwithstnding the question of tretment. In ddition, pst tretments (with lime or ny other tretments) hve probbly not reflected the importnce of tht prmeter. Consequently, they my hve been performed with inpproprite methods nd unsuitble controls, leding to conclusion tht the tretment itself mkes it impossible to obtin sufficiently homogeneous mteril. This full-scle test hs shown the fesibility of using the process on n industril scle, nd the benefits of processing the soil in centrl unit, which ensures n excellent level of homogeneity. Dike built with nturl soil In order to compre the properties of the lime-treted structure nd their evolution over time, the second experimentl embnkment ws built using the sme soil nd construction procedures, but without lime tretment. The mesured properties re reported in Tble Mechnicl performnces Mechnicl properties of the test embnkment mterils were performed in situ by pressuremeter mesurements, nd on cored smples using trixil testing. The cores were obtined using CETE NC soil investigtion rig (Sedidrill 500), on rubber trcked crwler equipped with double core brrel. Using tht kind of equipment, the core is not in contct with the rotting core brrel nd the drilling fluid. Two coring dimeters were used, 116 mm nd 80 mm. Pressuremeter test (Menrd) is sttic loding test performed by mens of cylindricl swelling probe introduced within verticl drilled hole. The vlues were obtined 28 dys, 6 months nd 1 yer fter the construction of the experimentl dikes, nd re reported in Tble 3. The increse of strength nd cohesion is demonstrted through these lst mesurements. Pressuremeter vlues indicte tht from nturl underconsolidted soil (rtio E M /p l * between 5 nd 8), lime tretment nd conservtion fter plcement produce n importnt Tble 3. Pressuremeter mesurements Structure Mesurement p f * p l * E M period (MP) (MP) (MP) E M /p l * Untreted 28 dys dike 6 months Limetreted 28 dys months dike 12 months

8 82 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction Tble 4. Trixil tests results (CD, residul vlues). Structure Mesurement period c (kp) ( ) Untreted dike 28 dys 0 (<10) dys 41 (fter 75 dys) 39.2 Lime-treted dike 61 6 months (fter 195 dys) months strength increse, mking the soil consolidted (rtio E M /p l * >10). In the sme time, trixil tests identify the initil, untreted soil s non- or little-cohesive (cohesion vlue is rbitrrily 0), wheres the cohesion fter lime tretment incresed to 41 kp fter 75 dys nd to 75 kp fter 12 months (Tble 4). Tble 5. Results of permebility mesurements. Untreted dike Lime-treted dike Mesurement period 28 dys (in m/s) 28 dys (in m/s) 6 months (in m/s) 12 months (in m/s) In situ tests : Vrible hed - 0, Constnt hed Tests on cored specimens : Trixil (CD) Permebility level nd erosion resistnce In situ nd lbortory permebility mesurements were recorded using severl methods. Two in situ methods were used. First, using double-pcker probe (see Fig. 10) t depth between -0.5 nd -1.1 m, the device pssing then through t lest 2 interfces between successive lyers. For this test, n 18-hour sturtion step ws pplied under hydrulic hed of 1.5 m, nd the mesurement ws done by following the decrese of wter level vs time (vrible hed Nsberg test). The second in situ method used ws constnt hed Nsberg test, where perforted pipe is pushed into the structure, to depth of 0.90 m. The hed of the pipe comes out of the surfce nd is covered by lid tht does not contct the pipe (Fig. 10b). Finlly, the verticl permebility ws lso mesured using the trixil test under sturted conditions. Tble 5 reports the recorded permebility vlues on the two structures. Very low permebility vlues were obtined for both structures, in the rnge of m/s. The similr orders of mgnitude cn be seen s evidence tht the lime tretment produces equivlent permebility levels s the nturl soil if the tretment nd plcement methodologies re pplied. Finlly, in situ horizontl permebility vlues show tht kneding compction using sheepfoot roller cn gurntee good overlpping of the successive lyers, voiding wter movement through interfces. b Fig. 11. MoJet externl erosion tests performed on untreted soil (, ccording usul prmeters) nd lime-treted embnkment slope (b, incresed flow to 2 l/min). The left pictures of ech series re tken before the test, the right ones t the end of the test. Erosion studies hve been led by IFSTTAR nd Irste. Interprettion of Hole Erosion Test (HET) results identify significnt increse in the criticl stress with lime tretment. 30 dys fter construction, the vlue ws multiplied by t lest 7 orders of mgnitude to more thn 800 P. The sme tendency is observed for in situ MoJet (Mobile Jets) erosion tests performed on the slopes of the dry dikes. The mount of soil recovered fter the test is divided by 25 times (norml flow of 600 ml/min during 15 min) or by 12.5 times (modified protocol: 5 min t 2 l/min), s it cn be seen on Figures 11 nd b. 4. The French DigueElite project Fig. 10. Double-pcker probe used for vrible hed Nsberg test (); schemtic view of the constnt hed Nsberg method (b). b Recently nd from these chievements, n mbitious French project clled DigueELite (which could be trnslted by Elite Dike ) ws lunched in June 2013 (logo on Fig. 12), in order to estblish innovtions tken

9 G. Herrier et l. Lime treted soil s n erosion resistnt mteril for hydrulic erthen structures 83 from the lime tretment technique nd technology in the field of flood protection levees. This projet is sponsored by Pôle Risques nd Axeler competitiveness hubs, nd includes the following prtners : ISL, ( hydrulic engineering office, project leder), Irste (French Reserch Public Institute), Lhoist Frnce (Lime Producer), EDF (French electric power compny nd owner of hydroelectric structures) nd Arcor Technologies (monitoring systems). Fig. 12. Logo of the French DigueElite project. The lime tretment is relevnt in the field of flood protection levees construction nd renovtion, first becuse constitutive rw mteril is soil. Qulity mterils re rrely vilble on the site nd their delivery involves significnt costs. Conversely, priori poor mterils, vilble in quntity, re difficult to recycle. Since the lte 90s, regultory constrints of French ntionl scope impose rtionl nd strictly controlled nturl resource exploittion. These considertions show tht the use of locl mterils, nmely the existing soil or sediment for the implementtion of hydrulic structures is mjor chllenge in the yers to come. The project ims to propose solution to improve the resistnce of protection dikes, s well for new structure s for existing ones, through developing n innovtive nd economiclly ttrctive dikes resistnt to ll filure mechnisms concept: DigueELITE. This concept is bsed on the development of rnge of new mterils, CONDYMAT (concept for new mterils Dyke ), bsed on the tretment of soils with lime. This tretment gives the soil, including locl soil of poor qulity, remrkble properties. At present, the performnce of soil-lime mteril in hydrulic structures re frgmented nd mostly limited to lbortory scle. Tht is why the formultion CONDYMAT, conditions for its mnufcturing site nd its limittions must be defined nd works full-scle must be designed nd tested to ddress ll issues relted to dikes nd levees: The gols of the project re within 3 yers: - reduce the breching risk due to externl erosion (overflow), internl erosion nd sliding; - propose new wy to design overflow resistnt zones, cting s spillwys for flood control - llow the reuse of locl mterils with poor engineering properties, lso sediments - reduce the overll construction nd mintennce costs of levee - ensure the esthetic, ecologicl nd lndscpe continuity. To meet these gols, ll the stges of civil engineering project of gret mgnitude hve to be controlled nd mnged : - control of the mterils themselves, tking into ccount ll mterils included in the term 'soil', nd its interction with vrious elements ; - the estblishment of concept, resolutely innovtive compred to the conventionl design of dm, to ssess the chrcteristics of the mteril, focusing on the efficcy nd sfety of the work; - control of implementtion, monitoring nd mintennce. The possibility of extending the pplicbility of the concept to the se dikes will be studied throughout the different phses of the project. These technicl spects must be ccompnied by broder considertions relted to both civil engineering project nd n innovtion project. The first jobsites of dikes construction, in South of Frnce, nd dike reinforcmeent (long the Schelde River in Belgium), will be chieved in Q2 Q Potentil Uses in the Future Thnks to the mechnicl improvement, erosion resistnce nd permebility levels conferred by lime tretment using the specific conditions described in this pper, it is possible to foresee future uses in lot of diverse hydrulic pplictions: - reuse of hevy clys in dike or dm foundtion, thnks to the bsence of differentil settlement, creep nd the stbility; - homogeneous embnkments in lime-treted soils for wrm nd dry countries, thnks to the reduction of shrinkge crcks, the improved workbility nd esier compction procedures; - construction of overtopping resistnt nd erosionresistnt dikes nd dms spillwys, externl blnkets of levees. 6. Conclusions Lime tretment of soils ws pplied from the 70 s, minly in US, in hydrulic structures restortion nd construction. It seems tht this technique ws forgotten in Europe. The design of cnls, levees nd dms cn only be done with the proper knowledge of the dequte properties of lime-treded soils nd their evolution. This pper described the corresponding results obtined in reserch progrm lunched by Lhoist in prtnership with Universities nd Reserch Institutes (Irste, IFSTTAR, LRPC ngers, CER Rouen, Université Libre de Bruxelles). A series of relevnt mechnicl, stbility, permebility nd erosion-resistnce properties of limetreted soils ws mesured, which llows the development nd the control of this technique, ccording to specific method of tretment nd compction. The lbortory experiments were followed by the

10 84 Proceedings of the South Bltic Conference on Dredged Mterils in Dike Construction construction of full-scle dike experiment chieved using the specified methodology nd technology, tht showed, on lime-treted silty soil structure: - the fesibility of the specific lime tretment nd plcement procedures t n industril scle, using dedicted mobile tretment plnt nd conventionl erthworks equipment; - the correltions between the lbortory observtions on lime-treted soil properties nd the rel scle - the benefits of lime tretment in terms of mechnicl improvement nd hydrulic behviour over time, compred to nturl (untreted) soil. Recently nd from these chievements, n mbitious French project clled DigueELite ws lunched in June 2013, in order to estblish innovtions in the subject of flood protection levees. This projet is sponsored by Pôle Risques nd Axeler competitiveness hubs, nd includes the following prtners: ISL, ( hydrulic engineering office, project leder), Irste (French Reserch Public Institute), Lhoist Frnce (Lime Producer), EDF (French electric power compny nd owner of hydroelectric structures) nd Arcor Technologies (monitoring systems). The gols of the project re within 3 yers: - reduce the breching risk due to externl erosion (overflow), internl erosion nd sliding ; - propose new wy to design overflow resistnt zones, cting s spillwys for flood control - llow the reuse of locl mterils with poor engineering properties, lso sediments - reduce the overll construction nd mintennce costs of levee - ensure the esthetic, ecologicl nd lndscpe continuity. References ANCOLD (1978) - Bulletin of the Austrlin Ntionl Committee On Lrge Dms, Issue N 51: 55p Benhmed, N., chevlier C., Bonelli, S.: Chpitre 5 - Erosion pr écoulement loclisé dns un conduit. In: Erosion des géomtériux, Trité MIM série Risques Nturels, (2012), Hermès Science Publiction, 37p. Bonelli, S., Benhmed, N. (2011): Piping flow erosion in wter retining structures, Interntionl Journl of Hydropower nd Dms, Vol. 18, No 3, pp Bonelli, S., Nicot, F., Fell, R., Hnson, G., Herrier, G., Mrot, D., Whl, T. Reltionship between the Erosion Properties of Soils nd Other Prmeters, Chpter 5 in : Erosion in Geomechnics Applied to Dms nd Levees. Edited by Stéphne Bonelli, ISTE Ltd - John Wiley & Sons, Inc, ch5/summry Chevlier, C., Hghighi, I., Mrtin, T., Reiffsteck, P. (2011): An Enhnced Crumb Test for better chrcterizing wter effects on soils. 15th Europen Conference on Soil Mechnics nd Geotechnicl Engineering, Athens, Greece. Cuisinier, O., Auriol, J.-C., Le Borgne, T., Deneele, D. (2011): Microstructure nd hydrulic conductivity of lime-treted silt. Engineering Geology, 123, pp Fleming, R., Sills, G., Stewrt, E. (1992). Lime Stbiliztion of Levee Slopes. In: Proceedings of the second intergency symposium on stbiliztion of soils nd other mterils, LA, pp to Gutschick K.A. (1978). Lime stbiliztion under hydrulic conditions. In : 4 th lime congress, Hershey (PA), pp Gutschick, K.A. (My 1985). Cnl lining stbiliztion proves successful. Pit & Qurry, pp Herrier, G.; Lesueur, D.; Puitti, D.; Auriol, J.-C.; Chevlier, C.; Hghighi, I.; Cuisinier, O. ; Bonelli, S.; Fry, J.-J. (2012) - Lime treted mterils for embnkment nd hrdfill dm, ICOLD 2012 Interntionl Symposium On Dms For A Chnging World, Kyoto 5-8 June Herrier, G., Bonelli, S. Internl erosion resistnce of soils treted with lime : n evolutive benefit. 21st Annul Meeting of Europen Working Group on Internl Erosion in Embnkment Dms & Their Foundtions, June 2013, Vienn, Austri Herrier, G., Puitti, D., Chevlier, C., Froumentin, M., Bonelli, S., Fry, J.-J. Lime tretment : new perspectives for the use of silty nd clyey soils in erthen hydrulic structures, in : WsserWirtschft, n 5, 2013, pp Proceedings 16. Deutsches Tlsperrensymposium, Mgdegurg, Germny, Mi Knodel, P.C. (1987). Lime in cnl nd dm stbiliztion. US Bureu of Reclmtion, Report No GR-87-10, (1987), 21p. Koussi, P. (1998): Comportement des sols fins compctés : pplictions ux remblis et ouvrges en terre, Ph.D. Thesis, University of Bordeux, 185 p. Little, D.L. (1995): Hndbook for Stbiliztion of Pvement Subgrdes nd Bse Courses with Lime, Dubuque (Iow), Published by Kendll/Hunt Publishing Compny. Perry J.P. (1977) - Lime tretment of dms constructed with dispersive cly soil, Trnsctions of the ASAE, Vol. 20: pp Phm, T.L. (2008): Erosion et dispersion des sols rgileux pr un fluide, Ph.D. Thesis, Ecole Ntionle des Ponts et Chussées, Pris, Frnce. Stpledon, D.; McGregor, P.; Bell, G.; Fell, R. (2005) - Geotechnicl Engineering of Dms, Tylor & Frncis. U.S. Army Corps of Engineers (2010). Alton to Gle Orgnized Levee Districts, Illinois nd Missouri (Continuing, Deficiency Corrections). USBR, U.S. Bureu of Reclmtion (1998) - Erth Mnul, Denver CO: 349 p. Verbrugge, J.-C., De Bel, R., Gomes Correi, A., Duvigneud, P.-H., Herrier, G. (2011): Strength nd micro observtions on lime treted silty soil, Proceedings of the 2011 GeoHunn Interntionl Conference, in Rod Mterils nd New Innovtions in Pvement Engineering (GSP 223).