A constitutive model for the deformation of a rock mass containing sets of ubiquitous joints

As part of the rock mass, the discontinuities inherently affect the strength and the deformational behavior of rock mass. Existing models can either handle the pre- or post-peak deformation of intact rock or joints alone; however, a model which can determine the failure mode and simulate the complete pre- and post-deformation of rock mass with multi-sets of joints is not yet available. This study focusses on rock mass with multi-sets of ubiquitous joints and establishes a mathematic model and an associated numerical implementation accounting for the anisotropy in strength and deformation induced by the existence of joints. Accordingly, an approach incorporating the existing models or methods to enable simulation of the complete deformation of rock mass is proposed. In addition to the pre- and post-peak deformation characteristics for intact rock, the pre-peak deformation of joint, such as the closure, shear and dilatancy effect as well as its post-peak deformation, such as the reduction on roughness, have also been taken into account. A series of comparisons validates that the proposed model is capable of presenting the joint-induced anisotropy in strength and deformation of rock mass, determining the possible failure modes and reasonably simulating the complete stress–strain relationship as well.