Modeling the Approach of Non‑mated Rock Fracture Surfaces Under Quasi‑static Normal Load Cycles

This paper examines the quasi-static behaviour of a non-mated rock fracture during the first and second loading cycles. Asperity deformation, substrate deformation, asperity interaction and gouge production are included in the modelling. The composite topography assumption is revisited, and the irregular fracture topography is idealized by representing the asperities as ellipsoidal surfaces. It is shown that the modelling can capture the closure behaviour and hysteresis response of rock fractures on both the first and second loading–unloading cycles with an acceptable accuracy. The model is then used to examine sensitivity of deformation behaviours to mechanical properties. It is shown that Young’s modulus of the rock is the most sensitive parameter with regard to the estimation of the closure behaviour of joints, followed by the compressive strength of the material, while the deformation is independent of the Poisson’s ratio variations in the range of ± 0.1. Moreover, while the closure behaviour is sensitive to variations in the joint roughness coefficient on the first loading cycle, this sensitivity reduces considerably on the second cycle.