Study on local shear mechanism in direct shear test of rough rock joints based on DEM

Rough joints widely exist in natural rock mass, and their shear mechanical properties control the safety and stability of rock mass. In the existing studies, the contribution of different protrusions to resisting shear stress is not mentioned. In this study, the local shear mechanism of different protrusions of rough joints in the shear process were well presented by combining quantitative and qualitative results using the discrete element method (DEM). Firstly, Barton's 10 standard roughness joint profiles were digitized. Rough joints were established using the modified smooth joint model (MSJM). The direct shear tests of joint specimens under constant normal stress were successfully conducted based on servo mode. Secondly, according to the test results, the law of shear stress was discussed. Then, the failure mode of joint specimen was discussed in detail based on the crack tracking module and force chain analysis. Next, the relationship between the number of cracks and shear stress was investigated. Finally, the variation law of average stress in different 10 segments of joints during shear was tracked based on the measuring circle function. The contribution of local joint segments in resisting shear stress is quantitatively described by 3 stress indexes.