Confinement-dependent behavior of a jointed rock mass: Insights from a 3D numerical perspective

Understanding the anisotropic characteristics and failure mechanisms of jointed rock masses is essential for reliable stability evaluation in rock engineering. However, accurately quantifying the influence of in-situ stress on the mechanical properties and failure modes of such systems remains a challenging and unresolved issue. To address this gap, we developed a discrete fracture network (DFN) model based on outcrop data from a dam site in southeastern Tibet. The representative elementary volume (REV) was determined using discrete-element analysis with mechanical upscaling, and a series of numerical triaxial compression tests were conducted on REV-scale models employing the synthetic rock mass (SRM) approach. Based on the anisotropy index, an advanced method is proposed for the quantitative evaluation of rock mass anisotropy and the analysis of the failure mechanisms in 3D jointed rock masses. Our results reveal that low confining pressures primarily induce joint slippage, whereas higher confining pressures reduce the anisotropy index of the jointed rock mass. Additionally, variations in crack orientation under different stress conditions highlight the pivotal role of confinement in governing fracture development. These findings offer new insights for enhanced stability evaluation in rock engineering.