Experimental and Numerical Investigation on Shear Failure Behavior of Rock-like Samples Containing Multiple Non-Persistent Joints

The instability of rock slopes and underground engineering structures is usually caused by shear sliding along discontinuities, such as joints or faults, which are usually non-persistent. It is important to study the shear failure behavior of non-persistent joints to better understand the instability mechanism of jointed rock masses. In this research, rock-like samples containing multiple non-persistent joints were prepared and used for direct shear tests under constant normal load. The test results showed that the shear failure of multiple non-persistent joints usually involves multiple coalescence modes of rock bridges, which are affected by joint configurations and normal stress. Under the same normal stress, the shear strength, and dilation behavior are mostly dominated by joint persistency, which essentially determines the roughness of the macroshear fracture surface. Furthermore, the acoustic emission characteristics of non-persistent joints were evaluated by the hit rate, energy rate, and b value. A lower b value, indicating a more intense shear failure, is usually related to a smaller joint persistency and medium joint spacing. Finally, the cracking process, force evolution, and micro-cracking mechanism of multiple non-persistent joints were revealed using particle flow code.