(1. School of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China；
2. School of Civil Engineering，Lanzhou University of Technology，Lanzhou，Gansu 730050，China)
Abstract：In this study，an indoor simulation test is conducted to monitor the swelling process of joint area which is backfilled with bentonite powder. The basic mechanism of swell-sealing of joint between blocks is investigated with microstructure analysis. According to the swelling test，the swelling stress development in the joints of blocks is anisotropic. The growth rate of swelling stress at joint area is higher than that of axial direction. The swelling stress at top surface，which is far away from the wetting surface，lags behind that at the bottom surface due to the water migration and sidewall friction. With the increasing of saturation degree，the joint areas are squeezed and compacted under the radial and axial swelling stresses of blocks. The final dry density of blocks decrease and of joint area increases. According to the microstructure analysis，the number of micropores in the soil aggregates decreases and the number of macropores and connected pores increase gradually from the block center to the joint area. A certain width of transition zone is formed between blocks and joint areas.
WANG Q，TANG A M，CUI Y J，et al. The effects of technological voids on the hydro-mechanical behaviour of compacted bentonite-sand mixture[J]. Soils and Foundations，2013，53(2)：232-245.
[4]
CHIJIMATSU M，SUGITA Y，MATSUMOTO K，et al. Mechanical and hydraulic properties of block joints of buffer[R]. [S. l.]：Power Reactor and Nuclear Fuel Development Corporation，PNC TN8410 98-058. 1998.
[6]
陈 宝，陈建琴，曹永超. 接缝对高压实膨润土工程屏障自封闭性能的影响[J]. 岩石力学与工程学报，2012，31(3)：618-624.(CHEN Bao，CHEN Jianqin，CAO Yongchao. Influence of joint on self-sealing behavior of highly compacted bentonite in engineering barrier[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(3)：618-624.(in Chinese))
[7]
GEET M V，BASTIAENS W，ORTIZ L. Self-sealing capacity of argillaceous rocks：Review of laboratory results obtained from the SELFRAC project[J]. Physics and Chemistry of the Earth Parts A/B/C，2008，33：S396-S406.
[9]
张虎元，王学文，刘 平，等. 缓冲回填材料砌块接缝密封及愈合研究[J]. 岩石力学与工程学报，2016，35(增2)：3 605-3 614. (ZHANG Huyuan，WANG Xuewen，LIU Ping，et al. Sealing and healing of compacted bentonite block joints in HLW disposal[J]. Chinese Journal of Rock Mechanics and Engineering，2016，35(Supp.2)：3 605-3 614.(in Chinese))
[12]
SABA S，BARNICHON J D，CUI Y J，et al. Microstructure and anisotropic swelling behaviour of compacted bentonite/sand mixture[J]. Journal of Rock Mechanics and Geotechnical Engineering，2014，6(2)：126-132.
[14]
SABA S，CUI Y J，TANG A M，et al. Investigation of the swelling behaviour of compacted bentonite-sand mixture by mock-up tests 1[J]. Revue Canadienne De Géotechnique，2014，51(12)：1 399-1 412.
[16]
LLORET A，VILLAR M V. Advances on the knowledge of the thermo-hydro-mechanical behaviour of heavily compacted“FEBEX”bentonite[J]. Physics and Chemistry of the Earth Parts A/B/C，2007，32(8/14)：701-715.
[10]
崔素丽，张虎元，刘吉胜，等. 混合型缓冲回填材料静力压实样的膨胀特性[C]// 第三届废物地下处置学术研讨会论文集. [S. l.]：[s. n.]，2010：431-439.(CUI Suli，ZHANG Huyuan，LIU Jisheng，et al. Experimental Study on Swelling Character of Statics-Compacted Bentonite-sand Mixture[C]// Proceedings of the 3rd Conference on Underground Waste Disposal. [S. l.]：[s. n.]，2010：431-439.(in Chinese))
[8]
SANDÉN T，BÖRGESSON L. System design of backfill-methods for water handling. KBSR-14-09[R]. Sweden：Swedish Nuclear Fuel and Waste Management Company，2014.
[5]
FURUICHI M，OKUTSU K，TANAKA T，et al. A Study of the sealing concept of high-level radioactive waste repository[J]. Journal of Geotechnical Engineering of Japan Society of Civil Engineers，1998，594：21-33.
[15]
SABA S，DELAGE P，LENOIR N，et al. Further insight into the microstructure of compacted bentonite-sand mixture[J]. Engineering Geology，2014，168(2)：141-148.
[1]
MARCIAL D，DELAGE P，CUI Y J. A laboratory study of the self sealing behaviour of a compacted sand-bentonite mixture[J]. Geomechanics and Geoengineering，2006，1(1)：73-85.
[3]
MOKNI N，BARNICHON J D，DICK P，et al. Effect of technological macro voids on the performance of compacted bentonite/sand seals for deep geological repositories[J]. International Journal of Rock Mechanics and Mining Sciences，2016，88：87-97.
[11]
张 明，张虎元，贾灵艳，等. 缓冲回填材料的室内制样方法研究[J]. 建筑材料学报，2012，15(5)：638-643.(ZHANG Ming，ZHANG Huyuan，JIA Linyan，et al. Method for sample preparation of buffer/backfilling materials in laboratory[J]. Journal of Building Materials，2012，15(5)：638-643.(in Chinese))
[13]
孙发鑫，陈正汉，秦 冰，等. 高庙子膨润土-砂混合料的三向膨胀力特性[J]. 岩石力学与工程学报，2013，32(1)：200-207.(SUN Faxin，CHEN Zhenhan，QIN Bin，et al. Characteristics of three- dimensional swelling pressure of GMZ bentonite-sand mixture[J]. Chinese Journal of Rock Mechanics and Engineering，2013，32(1)：200-207.(in Chinese))
2018, Vol. 37 
