混合型缓冲回填材料压实性能研究

 根据国外高放废物地质处置领域缓冲回填材料研发趋势，提出我国混合型缓冲回填材料开发新构想，即在纯膨润土中添加一定量的石英砂，期望在不显著降低渗透性能的前提下明显改善其热传导性能和力学强度。选取内蒙古高庙子膨润土(GMZ001膨润土)为主料，添加0%～50%含量的石英砂，采用标准击实试验和重型击实试验，研究混合土的动力压实特性；采用专门设计的压实模具，研究混合土在20和50 MPa压力下的静力压实特性。研究结果表明，不同掺砂率的膨润土–砂混合物，最大干密度与最优含水率存在统一的幂函数关系，而与压实方法及压实能大小无关。对于不同的压实方法及压实能大小，最优含水率与掺砂率之间存在线性关系。利用这些关系，就可以针对特定的压实目标选择适宜的压实方法。研究表明，高庙子膨润土掺加10%～30%的石英砂有助于改善压实质量，预计防渗性能也不会降低。

COMPACTION PROPERTIES OF BENTONITE-SAND MIXTURE AS BUFFER MATERIAL FOR HLW DISPOSAL

It is proposed that a mixture of bentonite and quartz sand might be a suitable backfill/buffer material for HLW disposal in China after reviewing the foreign research results,because bentonite can be optimized by addition of certain content of quartz sand to improve the heat conductivity and mechanical strength without an obvious increase in permeability. The compaction properties of GMZ001 bentonite-sand mixtures with a series of sand additions ranging from 0% to 50% are studied by standard and modified proctor compaction tests,and the static compaction tests under 20 MPa and 50 MPa pressures are designed. Test results show that the relationship between maximum dry density and optimum water content follows the same power function for all of the mixture specimens prepared in different compaction methods with different compaction efforts,while linear correlations exist for mixture specimens prepared in different compaction methods and compaction efforts. These correlation functions provide useful tools for convenient selection of compaction methods in practice. It is concluded that addition of 10%–30% quartz sand to GMZ001 bentonite can improve the compaction quality without altering the estimated impermeability of the backfill/buffer material.