Numerical experiments on rough joints in shear using a bonded particle model

Rock joints and rough faults exhibit two prominent characteristics. First, the relation between peak shear strength and normal stress is nonlinear; second, the peak dilatation angle is strongly dependent on normal stress. The accepted explanation for the dependence on normal stress relies on the influence of surface roughness. At low normal stress, the two sides of the joint “ride up” over each other with minimal damage to asperities, giving rise to a high dilatation angle and a high apparent-friction angle. At high normal stress, some asperities fail because their strengths are comparable to local stresses developed near contact points. The apparent friction and dilatation angles are therefore lower, as less “riding-up” occurs.