掺砂率对高放废物处置库中缓冲/回填材料收缩特性的影响

缓冲/回填材料的收缩特性对高放废物处置库的长期安全性和稳定性具有重要影响。以高庙子（GMZ） 膨润土-砂混 合物缓冲/回填材料为研究对象，探究了0~50%掺砂率下，试样蒸发失水过程中的收缩特性。试验结果表明：（1） 试样的水 分蒸发过程可分为常速率阶段、减速率阶段和残余阶段，且掺砂率对各阶段水分蒸发过程均有显著影响；（2） 掺砂率对试 样缩限值基本没有影响，但收缩应变却随着掺砂率的增大而减小；试样收缩系数在掺砂率为30%时达到最大，之后随掺砂 率的增大而减小；（3） 在不同掺砂率下，试样收缩均呈现出明显的各向异性；（4） 掺砂率越高，试样进气点对应的含水率 越大，最终孔隙比也越大。

Influence of Sand Mixing Ratio on the Shrinkage Characteristics of Buffer/Backfilling Materials in High-level RadioactiveWaste Geological Disposal

The shrinkage characteristics of bentonite-sand mixtures have a significant impact on the long-term safety and stability of HLW repositories. Taking Gaomiaozi (GMZ) bentonite-sand mixture as the research object and quartz sand as additive, the shrinkage characteristics of the sample during drying and water loss at 0-50% sand mixing ratio are explored. The results show that: (1) The water evaporation in the mixture is divided into the normal rate stage, the deceleration rate stage and the residual stage, and sand mixing ratio has a significant effect on each evaporation stage. (2) For the bentonite-sand mixtures, the effect of sand mixing ratio on the shrinkage limit is not significant, but the shrinkage strain decreases with the increase of sand mixing ratio. When the sand mixing ratio is greater than 30%, the shrinkage coefficient of soil sample decreases with the increase of soil mixing ratio. (3) The diametral shrinkage is greater than the axial shrinkage, showing obvious anisotropy. And the diametral shrinkage makes greater contribution to the volume shrinkage. (4) With the increase of sand mixing ratio, the soil sample is more easily to enter the unsaturated state from the saturated one, and the final void ratio also increases continuously