Joints, as inherent weak structural planes within rock masses, interact with bedding planes and govern the stability of layered rock slopes. Numerical models incorporating different levels of joint persistency and bedding dip angles were developed, followed by direct shear simulations under varying normal stresses. The coupled effects of multiple factors on mechanical response and failure mechanisms were systematically analyzed. The results show that shear strength increases with normal stress and decreases with joint persistency, exhibiting pronounced anisotropy. Microcrack evolution exhibits three distinct stages: elastic, initiation, and coalescence. The synergistic evolution of shear cracks along bedding planes and tensile cracks within the matrix primarily drives macroscopic failure. In contrast, tensile cracks along bedding planes and shear cracks within the matrix play a secondary role. The final failure is dominated by the concentration, expansion, and coalescence of shear microcracks, which penetrate bedding planes and form continuous failure zones. The bedding dip angle controls the geometric orientation of microcracks, normal stress governs the failure mode, and joint persistency affects the continuity of the failure path. The combined effects of these three factors determine the ultimate failure pattern and engineering stability of layered rock masses. These findings provide new insights into how joint persistence governs the shear behavior and failure characteristics of layered rock masses, offering both theoretical and technical support for engineering practices such as slope stability analysis.
Dong et al. (2026) studied this question.