Influence of fracture roughness and micro-fracturing on the mechanical response of rock joints: a discrete element approach

The closure and shear behaviors of 3D self-affine rock joints are simulated by the Discrete Element Method using PFC3D. First, a methodology to produce rough self-affine rock joints using DEM is presented then eight self-affine rough joints, having low and high values of roughness exponent, self-affine correlation length, and height variance, are considered. After the calibration of the elastic and fracture behaviors of an elementary volume formed from spherical discrete elements bonded by elastic beams, the numerical rock joints are submitted to closure tests at 14 and 21 MPa followed by a shear test at constant velocity and under constant normal load. Each DEM joint is tested using three different mechanical models: rigid, ideally elastic and elastic-fracturing. The use of these three models allows highlighting the distinct influences of the morphology, the joint stiffness and the micro-fracturing on the closure and shear behaviors of the joints.