(1. Key Laboratory of Mechanics on Disaster and Environment in Western China，The Ministry of Education，
Lanzhou University，Lanzhou，Gansu 730000，China；2. School of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China)
Abstract：Swelling of compacted bentonite buffer blocks plays a great role on the sealing of the high-level waste(HLW) depository，which is controlled by dry density and water content distribution in the blocks. Anisotropy in swell properties of bentonite blocks is inevitable because of the differential stress during compaction. This study provides a prototype of fan-shaped bentonite blocks compacted in specially designed mould for constructing HLW buffer barrier in China. The mixture of 70% bentonite and 30% quartz sand was prepared in a target moisture content of 12%，and compacted to a target dry density of 1.87 g/cm3. The compacted block was primarily cut in small cubes to measure dry density and moisture content，and then cut further into standard rings with specific directions to conduct a series of swelling tests. The results show that：(1) The compacted block has a better uniformity in dry density and moisture content distribution except the position far away from the pressure head. (2) Swell stress and strain distribution is highly corresponded to the dry density distribution，that is，the larger the dry density，the greater the swell. (3) Swell anisotropy is displayed in the vertical，or the compressed direction，rather than the horizontal directions of the block. By defining anisotropy coefficients of swell stress α and anisotropy coefficients of swell strain ?，statistic results indicate that ? = 0.856 to 0.926，while ? = 0.885 to 0.934，both of them are elevated with increase dry density.
[1] HANSEN J，KORKIALA-TANTTU L，KESKI-KUHA E，et al. Deposition tunnel backfill design for a KBS-3V repository[R]. Olkiluoto：Posiva Working Report，2010：53–63.
[2] OECD/NEA. Geological repositories：Political and technical progress workshop proceedings[R]. Sweden：Swedish Nuclear Fuel and Waste Management Company，2003：1–12.
[3] PUSCH R. Highly compacted sodium bentonite for isolating rock-deposited radioactive waste products[J]. Nuclear Technology，1979，45(9)：153–157.
[4] KOMINE H，OGATA N. Experimental study of swelling characteristics of compacted bentonite[J]. Canadian Geotechnical Journal，1994，31(4)：478–490.
[5] MARTíN P L，BARCALA J M. Large scale buffer material test：Mock-up experiment at CIEMAT[J]. Engineering Geology，2005，81(3)：298–316.
[6] PACOVSKY J，SVOBODA J，ZAPLETAL L. Saturation development in the bentonite barrier of the Mock-Up-CZ geotechnical experiment[J]. Physics and Chemistry of the Earth，2007，32(8–14)：767–779.
[7] CUI S L，ZHANG H Y，ZHANG M. Swelling characteristics of compacted GMZ bentonite–sand mixtures as a buffer/backfill material in China[J]. Engineering Geology，2012，141–142(2012)：65–73.
[8] 叶为民，SCHANZ T，钱立鑫，等. 高压实高庙子膨润土GMZ01的膨胀力特征[J]. 岩石力学与工程学报，2007，26(增2)：3 861–3 865.(YE Weimin，SCHANZ T，QIAN Lixin，et al. Characteristics of swelling pressure of densely compacted Gaomiaozi bentonite Gmz01[J]. Chinese Journal of Rock Mechanics and Engineering，2007，26(Supp.2)：3 861–3 865.(in Chinese))
[9] 秦 冰，陈正汉，刘月妙，等. 高庙子膨润土的胀缩变形特性及其影响因素研究[J]. 岩土工程学报，2008，30(7)：1 005–1 010.(QIN Bing，CHEN Zhenghan，LIU Yuemiao，et al. Swelling- shrinkage behavior of Gaomiaozi bentonite[J]. Chinese Journal of Geotechnical Engineering，2008，30(7)：1 005–1 010.(in Chinese))
[10] ENRES A. FEBEX Full-scale engineered barriers experiment in crystalline host rock，pre-operational Stage[R]. Madrid：Summary Report，1998.
[11] GRUMER M，SITZ P，RUMPHORST K. Design and emplacement of bentonite barriers[C]// International Conference of Underground Disposal Unit Design and Emplacement Processes for a Deep Geological Repository. Prague：IAEA，2008：13–1–13–9.
[12] HIDEKAZU A，SATOHITO T，YUMIKO Y，et al. Full-scale demonstration of ebs construction technology，(ii)design，manufacturing and transportation of pre-fabricated ebs module(PEM)[C]// International Conference of Underground Disposal Unit Design and Emplacement Processes for a Deep Geological Repository. Prague：IAEA，2008：12–1–12–12.
[13] 张虎元，张 明，程世红，等. 缓冲材料1/6扇形压实块[P]. 中国：ZL201220374874X，2013–01–16.(ZHANG Huyuan，ZHANG Ming，CHENG Shihong，et al. Buffer material 1/6 sector compacted block[P]. China：ZL201220374874X，2013–01–16.(in Chinese))
[14] 张虎元，张 明，程世红，等. 缓冲材料1/12扇形压实块[P]. 中国：ZL201220371712.0，2013–1–30.(ZHANG Huyuan，ZHANG Ming，CHENG Shihong，et al. Buffer material 1/12 sector compacted block[P]. China：ZL201220371712.0，2013–1–30.(in Chinese))
[15] 张虎元，梁 建，刘吉胜，等. 高庙子膨润土与砂混合物的击实性能研究[J]. 岩石力学与工程学报，2009，28(12)：2 585–2 592. (ZHANG Huyuan，LIANG Jian，LIU Jisheng，et al. Compaction properties of bentonite-sand mixture as buffer material for HLW disposal[J]. Chinese Journal of Rock Mechanics and Engineering，2009，28(12)：2 585–2 592.(in Chinese))
[16] 刘月妙，温志坚. 用于高放射性废物深地质处置的黏土材料研究[J]. 矿物岩石，2003，23(4)：42–45.(LIU Yuemiao，WEN Zhijian. Study on clay-based materials for the repository of high level radioactive waste[J]. Journal of Mineralogy and Petrology，2003，23(4)：42–45.(in Chinese))
[17] 张虎元，张 明，程世红，等. 缓冲材料1/12扇形压实模具[P]. 中国：ZL201220373629.7，2013–1–16.(ZHANG Huyuan，ZHANG Ming，CHENG Shihong，et al. Mould of buffer material 1/12 sector compacted block[P]. China：ZL201220373629.7，2013–1–16.(in Chinese))
[18] 张虎元，张 明，程世红，等. 缓冲材料1/6扇形压实模具[P]. 中国：ZL201220373505.9，2013–3–27.(ZHANG Huyuan，ZHANG Ming，CHENG Shihong，et al. Mould of buffer material 1/6 sector compacted block[P]. China：ZL201220373505.9，2013–3–27.(in Chinese))
[19] 张虎元，彭 宇，王学文，等. 冰–土混合法调配膨润土缓冲回填材料含水率研究[J]. 岩土力学，2016，37(增2)：144–150.(ZHANG Huyuan，PENG Yu，WANG Xuewen，et al. Research on ice-soil mixed method to adjust water content of bentonite as buffer/backfill material[J]. Rock and Soil Mechanics，2016，37(Supp.2)：144–150.(in Chinese))
[20] 王学文. 高放废物缓冲砌块压实性能研究[硕士学位论文][D]. 兰州：兰州大学，2017.(WANG Xuewen. Research on compacting properties of bentonite buffer block for HLW disposal[M. S. Thesis][D]. Lanzhou：Lanzhou University，2017.(in Chinese))
[21] JOHANNESSON，ERIK L，B?GRESSON，et al. SKB report R-99-12 Development of techniques for production of blocks with different shapes and sizes[R]. Stockholm：SKB，1998.
[22] 中华人民共和国国家标准编写组. GB/T50123—1999 土工试验方法标准[S]. 北京：中国计划出版社，1999.(The National Standards Compilation Group of People?s Republic of China. GB/T50123—1999 Standard for soil test method[S]. Beijing：China Planning Press，1999.(in Chinese))
[23] KENDALL D G，FELLER W. An introduction to probability theory and its applications[J]. Journal of the Royal Statistical Society，1951，114(2)：249–250.
[24] 叶为民，黄 雨，崔玉军，等. 自由膨胀条件下高压密膨胀黏土微观结构随吸力变化特征[J]. 岩石力学与工程学报，2005，24(24)：4 570–4 575.(YE Weimin，HUANG Yu，CUI Yujun，et al. Microstructural changing characteristics of densely compacted bentonite with suction under unconfined hydrating conditions[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(24)：4 570–4 575.(in Chinese))
[25] MICHRAFY A，DODDS J A，KADIRI M S. Wall friction in the compaction of pharmaceutical powders：measurement and effect on the density distribution[J]. Powder Technology，2004，148(1)：53–55.
[26] 孙发鑫，陈正汉，秦 冰，等. 高庙子膨润土–砂混合料得三向膨胀力特征[J]. 岩土力学与工程学报，2013，32(1)：200–207.(SUN Faxin，CHEN Zhenghan，QIN Bing，et al. Characteristics of three-dimensional swelling pressure of Gaomiaozi bentonite-sand mixture[J]. Chinese Journal of Rock Mechanics and Engineering，2013，32(1)：200–207.(in Chinese))
[27] HALLETT A H. Prediction and regulation by linear least-square methods[J]. International Journal of Forecasting，1963，2(1)：125–127.
2019, Vol. 38 
