Effects of bedding angle and confining pressure on the mechanical behavior, energy dissipation and micro damage evolution mechanism of layered rock mass under triaxial compression conditions

To reveal the anisotropy characteristics of mechanical behavior, energy evolution and fracture morphology of the layered rock mass during triaxial compression tests, MTS 815 mechanical test system is used to perform the relevant experimental studies on layered rock mass specimens with different bedding angles and confining pressures by combining energy analysis and CT scanning. Effects of bedding angle and confining pressure on the energy evolution characteristics of layered rock masses are deeply studied. With increasing bedding angle, the elastic energy, dissipative energy and total energy at the peak strength showed two changing trends: first increase and then decrease and then increase, first decrease and then increase. With increasing confining pressure, the anisotropy coefficient of elastic energy first decreases and then increases, the anisotropy coefficient of dissipative energy first decreases and then increases, and the anisotropy coefficient of total energy first increases and then decreases and then increases. The sensitivity of dissipative energy at peak strength to bedding angle is the highest and the sensitivity of elastic energy is the lowest. Micro-cracks reconstruction and quantitative characterization are first used to reveal the mechanism of confining pressure on the failure modes of layered rock specimens. At bedding angle = 45°, the two-dimensional crack area rate first increases and then decreases along the change of specimen height. When the confining pressure is 10 MPa, the dispersion degree of two-dimensional crack distribution along the specimen height is the largest, and the dispersion degree of two-dimensional crack along the specimen height is the least at 20 MPa.