<p>The stepped failure of slopes with intermittent joints represents a critical challenge in engineering geology, particularly concerning the fracture behavior of rock bridges and the stability assessment of such slopes. In this study, uniaxial compression numerical experiments are performed on specimens with varying rock bridge angles to investigate microcrack propagation, force chain evolution, and mechanical behavior. Analysis of the local displacement field allows identification of the angular ranges corresponding to shear, tension-shear, and tensile fracture modes, highlighting the evolution of rock bridge fracture behavior within distinct angular intervals. A mechanical model and theoretical analysis are developed to determine the critical angle governing fracture mode transition. This critical angle is shown to depend on tensile strength, internal friction angle, and in-situ stress conditions. Finally, by incorporating the critical angle, a limit equilibrium stability model is proposed for slopes under different fracture modes, encompassing slopes with complex fracture modes. This study offers geologists a practical tool for analyzing in-situ rock mass failure and provides a theoretical basis for hazard prevention and mitigation.</p>