Abstract Pre-compacted blocks of MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture are chosen as sealing/backfilling materials in the French concept of deep geological disposal for radioactive waste. Creating technological voids is normally unavoidable during installation in the disposal galleries, in the form of axial voids between compacted blocks and radial voids between the compacted blocks and the host rock. In this work, the aeolotropic swelling behaviour of compacted mixture with axial/radial technological voids was experimentally investigated. Results showed that the aeolotropy coefficient (ratio of radial to axial pressures) of samples without voids increased from 0.46 to 0.88 with the increasing dry density from 1.6 to 2.0 Mg/m3 due to the relatively concentrated macro-pores which defined a relatively lower local dry density in the side part. For the samples with axial/radial voids, their final axial swelling pressures were in agreement with the unique correlation with final dry density, regardless of the soil density heterogeneity. Samples with axial voids had a larger aeolotropy coefficient than samples without voids, due to the reduction of the orientation of clay particles upon hydration, while samples with radial voids had a smaller aeolotropy coefficient, due to the relatively lower dry density near the cell wall.

中文翻译：

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具有轴向/径向技术空隙的压实膨润土/粘土混合物的各向异性溶胀行为的试验研究

摘要 MX80 膨润土/Callovo-Oxfordian (COx) 粘土岩混合物的预压实块被选择作为法国放射性废物深层地质处置概念的密封/回填材料。在处理通道中安装过程中通常不可避免地会产生技术空隙，其形式为压实块之间的轴向空隙和压实块与主岩之间的径向空隙。在这项工作中，实验研究了具有轴向/径向技术空隙的压实混合物的各向异性膨胀行为。结果表明，随着干密度从1.6增加到2，无孔隙样品的各向异性系数（径向与轴向压力之比）从0.46增加到0.88。0 Mg/m3 由于相对集中的大孔，在侧部定义了相对较低的局部干密度。对于具有轴向/径向空隙的样品，无论土壤密度异质性如何，它们的最终轴向膨胀压力都与最终干密度的独特相关性一致。由于水化时粘土颗粒的取向降低，具有轴向空隙的样品比没有空隙的样品具有更大的各向异性系数，而具有径向空隙的样品由于靠近细胞壁的干密度相对较低而具有较小的各向异性系数。