A numerical study to investigate the influence of surface roughness and boundary condition on the shear behaviour of rock joints

The shear behaviours of rock joints with and without rock bolt support are numerically studied using the discrete element code PFC2D. A cohesive contact model was employed to reproduce the damage response of the synthetic intact rock (i.e. asperity degradation). We used the smooth-joint model to simulate the micro-scale roughness of the joint surface. We calibrated and validated the proposed numerical framework against the experimental results. A series of numerical constant normal stiffness (CNS) direct shear tests were conducted on idealised and natural rock joints to investigate the influence of the boundary condition on the shear behaviour of rock joints. In particular, the importance of CNS condition, surface roughness, asperity angle, and the initial normal stress were studied. Additionally, the shear and damage mechanism of bolted rock joints under constant normal load (CNL) and CNS condition was numerically investigated. The results presented show that the shear resistance of the joint increases under both CNL and CNS conditions, but at a high degree of roughness, no significant enhancement was observed on the value of peak shear stress.