Impact of Inclined Fault and Spherical Cavity on Sandstone Failure and Acoustic Response Under Triaxial Compression

Fault and cave are two traditional fracture structures in the original rock mass. To detect the specific failure characteristic of hard sandstone containing fault and cave, two centrally symmetrical sandstone blocks are cemented together to a cube combination specimen; then the true triaxial compression test is carried out, accompanied by acoustic emission technology monitoring the development process of micro fractures. The main results and conclusions are as follows: (1) The maximum horizontal strain coincided with the minimum principal stress, and different fault occurrences affected the development process of horizontal strain. (2) Secondary failure process could be divided into two stages, the first sudden stress drop phenomenon accelerated the first round of local failure, manifested by the relatively small axial strain, gradually decreasing b -values, higher AE (acoustic emission) counts, and sharp increase of RA (rising angle); the second round of failure was caused by the intrusion of the loading head, accompanied by the relatively large axial strain and more complex failure modes. (3) Different fault occurrences not only changed the initial growth rate of lateral strain and final distance between ε 2 and ε 3 , but also impacted the occurrence time of maximum RA and the change trend of AF (average frequency). (4) The inclined fault and cement fill controlled the first sub-strength of composite rock specimen, and different cavity filling conditions lead to various failure modes during the second round of destruction. The above conclusions can provide important references for safety evaluation and smooth construction of engineering projects under similar condition.