Abstract
Bentonite pellet mixtures are considered as one of the candidate sealing materials for deep geological disposals of radioactive waste. One of the particularities of this material is the initial heterogeneous distribution of pellets and porosity within the mixture, leading to complex hydro-mechanical behaviour. In this paper, the hydro-mechanical properties of GMZ bentonite pellet mixtures were investigated in the laboratory by carrying out water retention tests on pellet mixtures under constant-volume condition and single pellets under free swelling condition, as well as a infiltration test on a column specimen of pellet mixture. In the infiltration test, the relative humidity and radial swelling pressure were monitored at five heights, the axial swelling pressure was also recorded. The instantaneous profile method was applied to determine the unsaturated hydraulic conductivities. Results show that, in high suction range (> 10 MPa) the water retention curve of pellet mixture under constant-volume condition was comparable to that of a single pellet under free swelling condition, while in low suction range (< 10 MPa) the latter exhibits a much higher water retention capacity. Due to clogging of large pores, the unsaturated hydraulic conductivity decreases as suction decreases to around 25 MPa. However, with further suction decrease, the hydraulic conductivity increases continuously until the value at saturated state, as in the case of most unsaturated soils. The radial swelling pressure at different heights develops with local sudden increase and decrease, which was attributed to local rearrangement of pellets upon wetting. By contrast, as the axial swelling pressure was measured on the global surface of the specimen, it develops in a more regular fashion.
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References
Alonso EE, Hoffmann C, Romero E (2011) Hydromechanical behaviour of compacted granular expansive mixtures: experimental and constitutive study. Géotechnique 61(4):329–344. https://doi.org/10.1680/geot.2011.61.4.329
Andreasen AHM, Andersen J (1930) Relation between grain size and interstitial space in products of unconsolidated granules. Kolloid-Zeitschrift 50:217–228
Bian X, Cui YJ, Li XZ (2019) Voids effect on the swelling behaviour of compacted bentonite. Géotechnique 67(7):593–605. https://doi.org/10.1680/jgeot.17.p.283
Blatz JA, Cui YJ, Oldecop L (2008) Vapour equilibrium and osmotic technique for suction control. Geotech Geol Eng 26:661–673. https://doi.org/10.1007/s10706-008-9196-1
Chen L, Liu YM, Wang J, Gao SF, Xie JL, Ma LK, Zhao XG, Li YW, Liu J (2014) Investigation of the thermal-hydro-mechanical (THM) behavior of GMZ bentonite in the China-Mock-up test. Eng Geol 172:57–68. https://doi.org/10.1016/j.enggeo.2014.01.008
Cui YJ, Tang AM, Loiseau C, Delage P (2008) Determining the unsaturated hydraulic conductivity of a compacted sand–bentonite mixture under constant-volume and free-swell conditions. Phys Chem Earth 33(S1):S462–S471. https://doi.org/10.1016/j.pce.2008.10.017
Daniel DE (1982) Measurement of hydraulic conductivity of unsaturated soils with thermocouple psychrometers. Soil Sci Soc Am J 20(6):1125–1129. https://doi.org/10.2136/sssaj1982.03615995004600060001x
Delage P, Howat M, Cui YJ (1998) The relationship between suction and swelling properties in a heavily compacted unsaturated clay. Eng Geol 50(1–2):31–48. https://doi.org/10.1016/S0013-7952(97)00083-5
Delage P, Cui YJ (2008) An evaluation of the osmotic method of controlling suction. Geomech Geoeng 3(1):1–11. https://doi.org/10.1080/17486020701868379
Dixon DA, Gray MN, Hnatiw D (1992) Critical gradients and pressures in dense swelling clays. Can Geotech J 29(6):1113–1119. https://doi.org/10.1139/t92-129
Ferrari A, Seiphoori A, Rüedi J, Laloui L (2014) Shot-clay MX-80 bentonite: an assessment of the hydro-mechanical behaviour. Eng Geol 173:10–18. https://doi.org/10.1016/j.enggeo.2014.01.009
García-Siñeriz JL, Villar MV, Rey M, Palacios B (2015) Engineered barrier of bentonite pellets and compacted blocks: state after reaching saturation. Eng Geol 192:33–45. https://doi.org/10.1016/j.enggeo.2015.04.002
Hoffmann C, Alonso EE, Romero E (2007) Hydro-mechanical behaviour of bentonite pellet mixtures. Phys Chem Earth 32(8–14):832–849. https://doi.org/10.1016/j.pce.2006.04.037
Imbert C, Villar MV (2006) Hydro-mechanical response of a bentonite pellets/powder mixture upon infiltration. Appl Clay Sci 32(3–4):197–209. https://doi.org/10.1016/j.clay.2006.01.005
Johannesson LE, Börgesson L, Goudarzi R, Sandén T, Gunnarsson D, Svemar C (2007) Prototype repository: a full scale experiment at Äspö HRL. Phys Chem Earth 32:58–76. https://doi.org/10.1016/j.pce.2006.04.027
Karnland O, Nilsson U, Weber H, Wersin P (2008) Sealing ability of Wyoming bentonite pellets foreseen as buffer material—laboratory results. Phys Chem Earth 33:S472–S475. https://doi.org/10.1016/j.pce.2008.10.024
Li ZZ, Su G, Zheng Q, Nyuyen TS (2019) A dual-porosity model for the study of chemical effects on the swelling behaviour of MX-80 bentonite. Acta Geotech. https://doi.org/10.1007/s11440-019-00762-5(in press)
Liu ZR, Ye WM, Zhang Z, Wang Q, Chen YG, Cui YJ (2019) Particle size ratio and distribution effects on packing behaviour of crushed GMZ bentonite pellets. Powder Technol 351:92–101. https://doi.org/10.1016/j.powtec.2019.03.038
Liu ZR, Cui YJ, Ye WM, Zhang Z, Wang Q, Chen B (2020) Investigation on vibration induced segregation behaviour of crushed GMZ bentonite pellet mixtures. Constr Build Mater 241:117949. https://doi.org/10.1016/j.conbuildmat.2019.117949
Molinero-Guerra A, Mokni N, Delage P, Cui YJ, Tang AM, Aimedieu P, Bernier F, Bornert M (2017) In-depth characterisation of a mixture composed of powder/pellets MX80 bentonite. Appl Clay Sci 135:538–546. https://doi.org/10.1016/j.clay.2016.10.030
Molinero-Guerra A, Cui YJ, Mokni N, Delage P, Bornert M, Aimedieu P, Tang AM, Bernier F (2018) Investigation of the hydro-mechanical behaviour of a pellet/powder MX80 bentonite mixture using an infiltration column. Eng Geol 243:18–25. https://doi.org/10.1016/j.enggeo.2018.06.006
Molinero-Guerra A, Aimedieu P, Bornert M, Cui YJ, Tang AM, Sun Z, Mokni N, Delage P, Bernier F (2018) Analysis of the structural changes of a pellet/powder bentonite mixture upon wetting by X-ray computed microtomography. Appl Clay Sci 165:164–169. https://doi.org/10.1016/j.clay.2018.07.043
Molinero-Guerra A (2018) Experimental and numerical characterizations of the hydro-mechanical behavior of a heterogeneous material: pellet/powder bentonite mixture. University of Paris-Est, Paris
Niu WJ, Ye WM, Song X (2019) Unsaturated permeability of Gaomiaozi bentonite under partially free-swelling conditions. Acta Geotech. https://doi.org/10.1007/s11440-019-00788-9(in press)
Salo JP, Kukkola T (1989) Bentonite pellets, an alternative buffer material for spent fuel canister deposition holes. NEA/CEC Workshop “Sealing of Radioactive Waste Repositories”. (Braunschweig, Germany), OECD, Paris
Seiphoori A, Ferrari A, Laloui L (2014) Water retention behaviour and microstructural evolution of MX-80 bentonite during wetting and drying cycles. Géotechnique 64(9):721–734. https://doi.org/10.1680/geot.14.P.017
Sun HQ, Mašín D, Najser J, Neděla V, Navrátilová E (2019) Fractal characteristics of pore structure of compacted bentonite studied by ESEM and MIP methods. Acta Geotech. https://doi.org/10.1007/s11440-019-00857-z(in press)
Tang AM, Cui YJ (2005) Controlling suction by the vapour equilibrium technique at different temperatures and its application in determining the water retention properties of MX80 clay. Can Geotech J 42:1–10. https://doi.org/10.1139/T04-082
Van Geet M, Volckaert G, Roels S (2005) The use of microfocus X-ray computed tomography in characterising the hydration of a clay pellet/powder mixture. Appl Clay Sci 29(2):73–87. https://doi.org/10.1016/j.clay.2004.12.007
Villar MV, Lloret A (2004) Influence of temperature on the hydro-mechanical behaviour of a compacted bentonite. Appl Clay Sci 26(1–4):337–350. https://doi.org/10.1016/j.clay.2003.12.026
Volckaert G, Bernier F, Alonso E, Gens A, Samper J, Villar MV, Martín PL, Cuevas J, Campos R, Thomas HR, Imbert C, Zingarelli V (1996) Thermal-hydraulic-mechanical and geochemical behaviour of the clay barrier in radioactive waste repositories (model development and validation). Nuclear Science and Technology. EUR 16744. Commission of the European Communities, Luxembourg. 722 pp
Wan M, Ye WM, Chen YG, Cui YJ, Wang J (2015) Influence of temperature on the water retention properties of compacted GMZ01 bentonite. Environ Earth Sci 73(8):4053–4061. https://doi.org/10.1007/s12665-014-3690-y
Wan M, Delage P, Tang AM, Talandier J (2013) Water retention properties of the Callovo-Oxfordian claystone. Int J Rock Mech Min Sci 64(12):96–104. https://doi.org/10.1016/j.ijrmms.2013.08.020
Wang Q, Cui YJ, Tang AM, Barnichon JD, Saba S, Ye WM (2013) Hydraulic conductivity and microstructure changes of compacted bentonite/sand mixture during hydration. Eng Geol 164:67–76. https://doi.org/10.1016/j.enggeo.2013.06.013
Wang SW, Zhu W, Fei K, Xu CY, Zhang N (2018) Study on non-darcian flow sand-clay mixtures. Appl Clay Sci 151:102–108. https://doi.org/10.1016/j.clay.2017.10.028
Ye WM, Schaze S, Qian LX, Wang J, Arifin Y (2007) Characteristics of swelling pressure of densely compacted gaomiaozi bentonite GMZ01. Chin J Rock Mechan Eng 26:3861–3865 (in Chinese)
Ye WM, Cui YJ, Qian LX, Chen B (2009) An experimental study of the water transfer through confined compacted GMZ bentonite. Eng Geol 108(3–4):169–176. https://doi.org/10.1016/j.enggeo.2009.08.003
Ye WM, Chen YG, Chen B, Wang Q, Wang J (2010) Advances on the knowledge of the buffer/backfill properties of heavily-compacted GMZ bentonite. Eng Geol 116(1):12–20. https://doi.org/10.1016/j.enggeo.2010.06.002
Zhang Z, Ye WM, Liu ZR, Chen BC, Cui YJ (2018) Influences of PSD curve and vibration on the packing dry density of crushed bentonite pellet mixtures. Constr Build Mater 185:246–255. https://doi.org/10.1016/j.conbuildmat.2018.07.096
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The financial supports of the National Nature Science Foundation of China (41527801, 41672271 and 41807237) and the Shanghai Pujiang Program (18PJ1410200) are greatly acknowledged.
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Liu, ZR., Cui, YJ., Ye, WM. et al. Investigation of the hydro-mechanical behaviour of GMZ bentonite pellet mixtures. Acta Geotech. 15, 2865–2875 (2020). https://doi.org/10.1007/s11440-020-00976-y
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DOI: https://doi.org/10.1007/s11440-020-00976-y