Characterizing the anisotropic mechanical behavior and failure of synthetic rock mass under true triaxial compression using a DEM-DFN model

A comprehensive understanding of the anisotropic mechanical behavior and failure of jointed rock masses under varying stress paths is essential for the rational design and safe construction of rock excavations. In contrast to previous studies that primarily focused on the anisotropy of jointed rock masses under uniaxial loading conditions, this study examines their anisotropic mechanical response subjected to true triaxial compression, employing a coupled Discrete Element Method-Discrete Fracture Network (DEM-DFN) model. A novel numerical scheme was developed for true triaxial compression simulations on Synthetic Rock Mass (SRM) specimens incorporating six distinct loading paths defined along three orthogonal directions in stress space, the initial confining pressure, and the stress ratio, which is directly associated with the Lode angle. The mechanical behavior and failure characteristics of the SRM specimen in the benchmark case were first presented, followed by a detailed analysis of the effects of various contributing factors. The anisotropic mechanical behavior of SRM specimen under true triaxial compression conditions was quantitatively characterized using the proposed anisotropy index accompanied with the trajectory of true triaxial compressive strength on the π-plane. Furthermore, the anisotropic characteristics of SRM specimen were studied from the perspectives of stress-induced deformation anisotropy, and energy evolution concerning the variation in energy storage capacity under different loading conditions. This study improves the understanding of the anisotropic mechanical behavior and failure of complex jointed rock masses under true triaxial stress paths, thereby providing a scientific basis for the support and excavation design of deep rock engineering.