Effect of crack surface slip and shear dilatation on damage and failure of rocks

The current research on the impact of slip and dilatancy along fissure surfaces in discontinuously fractured rock masses on rock damage and failure is insufficient. This study improves the macroscopic damage model of rock masses in two aspects by employing fracture and damage mechanics. Initially, we considered that during slip under uniaxial compression, the irregular rough asperities on the fissure surface cause frictional energy loss. Secondly, based on the Bardon dilatancy model, we took into account the fact that closed sliding fissures generate certain normal dilatancy displacement, resulting in the loss of strain energy. Furthermore, using the Mohr-Coulomb rock micro-element strength criterion and assuming that the micro-element strength follows a Weibull distribution, a meso-damage model for the rock mass was constructed. Finally, based on Lemaitre's strain equivalence hypothesis, a macro-meso coupled damage model was developed, considering fissure slip and dilatancy. Comparison with experimental data shows that this model can show the uniaxial compression mechanical behavior of rock masses well. The analysis of parameter sensitivity of such parameters as the inclination, length, internal friction angle, and dilatancy angle of rock fissures demonstrates that considering slip and dilatancy along fissure surfaces is crucial for studying the uniaxial compression mechanical properties of rock masses. This research provides a reference for accurately explaining the physical and mechanical behavior of fissure surfaces in fractured rock masses under uniaxial compression.