Influence of joint geometry and roughness on the multiscale shear behaviour of fractured rock mass using particle flow code

The geometry of natural discontinuities varies greatly, and the shear properties of joints are influenced by their geometry and roughness. The majority of the existing discrete fracture network (DFN) models simplify joints as flat (planar in 3D or linear in 2D) structures. Therefore, a rough discrete fracture network (RDFN) model that considers the variability in joint geometry and roughness was introduced here. Three types of RDFN models were established, and numerical shear testing was performed using a particle flow code (PFC). Then, the multiscale mechanical behaviours of RDFN models during shear testing was numerically simulated and compared with that of DFN models by using PFC2D code. The numerical results show that the proposed RDFN model can efficiently characterize the geometry of the rough joints. The peak shear strength of the RDFN model was improved over that of the DFN model. The magnitudes of the peak shear stresses of the RDFN models at various scales were higher than that of the DFN model. According to the comparison, the shear capacity of a fractured rock mass would be underestimated if joint roughness is ignored.