A dynamic damage constitutive model for a rock mass with persistent joints

The strength and deformability of a rock mass is one of the most important problems in the rock engineering. Rock masses are usually fractured as a result of many flaws of different scales through various geological processes. The joints and microcracks are the macroscopic and mesoscopic flaws, respectively. In this study, a dynamic damage constitutive model for jointed rock mass is proposed and applied to the rock mass models with many persistent joints. First, the mesoscopic damage variable and macroscopic damage tensor are introduced to describe the damage caused by microcracks and joints, respectively. Second, the coupled damage variable (tensor) is obtained with Lemaitre strain equivalence hypothesis. Finally, the dynamic damage constitutive model for the rock mass with persistent joints is proposed based on Taylor-Chen-Kuszmaul (TCK) model. The results show that the initial deformation stage of the samples coincides with each other under the different load strain rate. A further increase of strain increases the climax strength and the total strain of the materials. The parameter is studied further from the number of joints in rock mass, the climax strength gradually decreases with increase in joint number, but the reduction level gradually becomes less and tends to be a constant. The above conclusions agree well with the existing experimental and theoretical results.