Effect of interface morphology on the heterogeneous development of bedding-perpendicular joints in soft-hard interbedded strata

Bedding-perpendicular joints (BPJs) in soft-hard interbedded masses exhibit heterogeneous distribution. Statistical analysis revealed the impacts of interface morphology on the heterogeneity distribution of joint spacing and strike. It was observed that there existed a negative exponential relationship between joint spacing and roughness of macroscopic interface morphology. Furthermore, the heterogeneity of the microscopic interface morphology also led to a decrease in joint spacing. Additionally, the micro-heterogeneity of the interface morphology has an inducing effect on the fracture direction of the rock, which is one of the main reasons for the discrete distribution of joint strikes. The 3D printed soft-hard interbedded rock mass model reproduced the initiation, expansion and penetration of BPJs. It can be found that the zone of tensile stress concentration near the interface depression was positively correlated with the morphology value of the undulating body. With the progressive filling of the BPJs, the joint initiation points appeared alternately near the upper and lower interfacial concave points of the hard brittle layer. Furthermore, the filling order of BPJ was influenced by the mean stress of the section where the joint was located, highlighting the controlling effect of microscopic interface morphology on the heterogeneous progressive filling of BPJs.