DEM modelling of the shear behaviour of rock joints

The constitutive behaviour of rock discontinuities is highly controlled by the roughness of the surface. Its contribution is a combination of two aspects of overall roughness: the morphology of the surface (or shape) and the strength of the asperities (related to the strength of the surrounding rock). Appropriate description of rock joint behaviour entails accurate description of the morphology and provision for asperity degradation. In this study, we propose to take advantage of the latest developments in numerical techniques. The DEM code PFC3D has been used to generate a numerical replica of a joint. Microproperties have been calibrated to mimic the physical rock. The morphology has been obtained using 3D photogrammetry. The derived triangulated surface is then introduced into PFC3D to generate a synthetic rock joint. The recently developed Smooth Joint contact model is used to describe the interaction between particles lying on opposite side of the surface. The smooth joint model allows to get rid of the artificial roughness introduced by particle discretization. The generated discrete model replicates the two aspects of overall roughness: shape and strength. Direct shear tests are then performed to characterise its mechanical behaviour. Results of the simulations are presented