高放射性核废料深地质处置库中的缓冲层由膨润土块堆砌构成, 而块体由膨润土粉末压制而成, 其强度可能存在各向异性. 采用直接拉伸试验方法, 测得压实高庙子膨润土在不同条件下的抗拉强度, 探讨了干密度和含水率对抗拉强度各向异性的影响, 并进行了机理分析. 试验结果表明: 随着含水率的增加, 抗拉强度先增大后减小, 存在一个峰值; 抗拉强度随着干密度的增加而增大; 当拉力方向与制样压实力方向垂直时, 试样的抗拉强度大于拉力方向与压实力平行时的抗拉强度, 并且在同一含水率下, 抗拉强度各向异性的程度随干密度的增加而增大. 原因在于压实过程中蒙脱石层叠体排列趋于一个方向, 导致各向异性显著. 研究成果可为我国核废料处置库膨润土块体在运输和吊装过程中的抗拉强度特性提供参考数据.

The buffer layer in a deep geological repository used in the disposal of high-level radioactive waste (HLW) is composed of bentonite blocks that are compressed with bentonite powders, and their strength may show anisotropic characteristics. In this study, the tensile strength of compacted Gaomiaozi (Gaomiaozi, China) bentonite under different conditions was measured by direct tensile tests, and the effects of dry density and moisture content on the anisotropy of tensile strength were analyzed and discussed. The results showed that the tensile strength initially increased and then decreased with increasing water content, during which a peak value was observed. The tensile strength also increased with increasing dry density. When the direction of the tensile force was perpendicular to that of the compaction force, the tensile strength was greater than when the direction of the tensile force was parallel to that of the compaction force. In addition, under the same water content, the degree of anisotropy of tensile strength increased with increasing dry density. This could be explained by the fact that montmorillonite laminae tend to be arranged in a direction perpendicular to that of the compaction force, leading to significant anisotropy. These results can provide a reference for assessing the tensile strength characteristics of bentonite blocks in transportation and hoisting processes in the disposal of HLW in China.