Numerical modelling of cyclic shear behaviour of rock joints under constant normal stiffness condition

The cyclic shear behaviour of rock joints was investigated in the laboratory under constant normal stiffness condition for low and high values of initial normal stress and asperity angle. The Universal Distinct Element Code was applied (UDEC) to simulate the laboratory behaviour using two available models. The predicted shear stress, normal stress, and dilation with shear displacement were compared with experimental results. It was observed that the change in the shear strength and recovery of dilation upon load reversal are simulated using the Coulomb Slip model for low values of initial normal stress and asperity angle when the shearing mechanism was sliding over asperities. However, the Continuously Yielding model replicated better cyclic shear behaviour of rock joints under breaking mechanism (i.e. high levels of initial normal stress and asperity angle), as this model represents progressive damage of asperities during shearing and approaching to the residual friction angle when asperities are fully degraded.