Numerical investigation of strength and micro-cracking behavior of anisotropic sandstone under true triaxial stress

Anisotropy is a common behavior of bedded rock in underground engineering. Evaluating the influence of bedding plane on both mechanical property and failure behavior of anisotropic rock under true triaxial stress is of great importance. In this study, a comprehensive numerical investigation is conducted utilizing a three-dimensional discrete element method to explore how minimum principal stress, intermediate principal stress, and inclination angle of the bedding plane affect the deformation and strength properties, failure pattern, and associated micro-cracking process in anisotropic rock. True triaxial simulations on a numerical model possessing seven different bedding plane inclination angles are conducted under various stress conditions. The results reveal that the peak strength and failure mode are governed by the coupled effects of principal stresses and bedding plane inclination. A U-shaped strength variation with inclination angle is observed under low differential stress and the trend gradually diminishes as differential stress increases. The failure plane changes from bedding-controlled to intermediate-principal-stress-controlled with increasing differential stress. Micro-cracking analysis further elucidates the underlying mechanisms driving these macroscopic behaviors.