Abstract:

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.

Key words: Gaomiaozi bentonite, tensile strength, anisotropy, prediction, unsaturated soil