Shear-induced anisotropy analysis of rock masses containing non-coplanar intermittent joints

The macroscopic mechanical behavior of granular materials is closely related to the fabric anisotropy and contact force anisotropy. In order to investigate the microevolution of fabric and force anisotropy of rock masses containing non-coplanar intermittent joints under direct shear loading, this paper establishes a numerical model using the particle flow code (PFC) based on the distinct element method (DEM) and investigates the effects of non-coplanar intermittent joints on the evolutions in the fabric and force anisotropy and the distributions of contact forces of rock specimens by setting up specimens with different ligament angles of joints. Meanwhile, the shear strength, deformation characteristics and failure mode, energy dissipation were analyzed to deepen the understanding of the macroscopic mechanical behavior of the specimens from the microscopic mechanism. Three anisotropic tensors \({a}_{ij}^{c}\) $a_{\mathit{ij}}^c$ , \({a}_{ij}^{n}\) $a_{\mathit{ij}}^n$ and \({a}_{ij}^{t}\) $a_{\mathit{ij}}^t$ are defined to characterize the anisotropic behavior of the granular materials which can show the evolution law of fabric and mechanical anisotropy of the system under direct shear load. The findings indicate that the degree of fabric anisotropy increases with increasing ligament, and the length of the load side significantly influences the initial mechanical anisotropy of the specimen. Concurrently, a rise in the ligament angle impedes the progression of anisotropy within the specimen, leading to a substantial reduction in the macroscopic mechanical strength of the rock.