Experimental and numerical research on the anisotropic compressive mechanical behavior of layered rock

To study the anisotropic mechanical characteristics of layered rock, typical phyllite specimens with bedding plane angles of 0°, 30°, 45°, and 90° were prepared, and triaxial loading and unloading tests under different confining pressures were conducted. Based on the experimental results, the anisotropic mechanical properties and fracture mechanisms of phyllite under different stress paths were analyzed. The results shown that under varying confining pressures, the elastic modulus and compressive strength of phyllite initially decreased and subsequently increased with the increase of bedding plane angle; With the increase in confining pressure, the compressive strength enhanced under both triaxial loading and unloading conditions; The failure modes of phyllite with different bedding plane angles exhibited significant anisotropy; While the residual friction angle exceeded the peak value in triaxial loading tests and showed the opposite trend in unloading tests, the residual cohesive strength remained consistently lower than the peak under different stress paths. Finally, a numerical model for simulating triaxial loading of phyllite was developed using PFC^2D. The numerical simulation results shown a high degree of consistency with the experimental findings, and the post-peak crack counts with different bedding plane angles were analyzed. The occurrence of the layered and matrix composite failure mode was closely associated with the strength ratio between the rock matrix and the bedding plane.