Coupled damage and friction model for persistent fractured rocks considering multi-scale structures

A coupled damage and friction constitutive model for persistent jointed rocks based on a two-step homogenization technique is proposed considering the influences of anisotropic damage growth of intact rocks, mobilized dilatancy behavior of microcracks, recovery of normal stiffness due to normal closure of closed microcracks, mobilized degradation of multi-order asperities of joints, shear dilatancy of joints, and interaction between joints and rocks. The effects of multi-scale structures (i.e., joint and microcracks) on the deformation characteristics of fractured rocks are better addressed by the proposed model. The existing laboratory triaxial compression tests on crystalline rocks, shear tests on joint specimens, together with triaxial compressive strength tests on Martinsburg slate under different confining pressures and joint configurations, are used to validate the proposed model. The good agreements between the model predictions and the test results demonstrate the accuracy of the proposed model.