Transversely Isotropic Slates Subject to Compressive Differential Cyclic Loading, Part II: Numerical Modeling of Mechanical Responses and AE Behaviors

Anisotropic behaviors of layered rocks, characterized by the distinct mechanical responses to varying loading directions, have been widely studied in laboratory tests. However, understanding the microscale failure mechanisms of beddings and rock matrices is still challenging in laboratory scale. In this study, we present a numerical modeling based on PFC^3D to investigate the mechanical responses of slates with five bedding angles (0°, 30°, 45°, 60°, 90°) under differential cyclic loading (DCL). The beddings and matrices are modeled using the same contact model to ensure the comparability of parameters, with the weakened parameters of beddings reasonably determined through X-ray diffraction (XRD). The damage evolution paths are characterized by the degradation of the bond diameter. The simulation results replicate realistic stress–strain curves documented in laboratory tests. We develop an acoustic emission (AE) algorithm for respectively monitoring the AE events occurring in beddings and matrices. Additionally, the release of the bond energy is captured to determine the b-values in simulation, and experimental data are used to validate its rationality. Finally, the macroscopic failure patterns obtained from numerical simulations are compared to the failed samples in laboratory test and the nuclear magnetic resonance (NMR) results, demonstrating a consistent correlation and verifying the validity of the proposed model.