Investigation on failure mechanism and mechanical response of layered rocks based on AE monitoring and 3D numerical simulation

The deformation and failure mechanisms of layered rocks under the combined effects of bedding-plane orientation and confining pressure are crucial for maintaining the stability of both surface and underground geotechnical structures. In this study, rock specimens with different bedding orientations were fabricated using a custom-designed compaction device, and uniaxial compression tests combined with acoustic emission (AE) monitoring were conducted. Furthermore, the microscopic failure processes of layered rock under varying confining pressures and bedding orientations were simulated using three-dimensional particle flow code (PFC3D). The results reveal that, near the peak stress, the slopes of the cumulative AE ring-down counts and cumulative energy curves rose sharply, indicating that the surface cracks are expanding rapidly. The dominant AE frequencies were concentrated in two low-frequency bands and one high-frequency band, with the low-frequency components prevailing. Under uniaxial compression, the peak strength of the specimens exhibited a 'U'-shaped dependence on bedding angle, whereas the peak AE ring-down count followed an inverted 'n'-shaped pattern. The peak AE ring-down count displayed an "m"-shaped pattern under confining pressure. Moreover, increasing confining pressure reduced the peak AE activity and attenuated the effect of bedding orientation.