<p>The stability of rock slopes is heavily influenced by the shearing characteristics of rock joints, which dictate the mechanical properties of discontinuous rock masses. This study focuses on examining the failure mechanism of rock joints, particularly those with rough surfaces. Through analysis of experimental data from existing literature, the relationship between shear stress and shear displacement is established. A damage-based mechanical model is proposed, utilizing rheological elements and incorporating asperity angles. A mathematical equation is derived to enhance the predictive capabilities of the model. Validation results demonstrate the model’s effectiveness in capturing the mechanical behavior of rock joints based on the referenced data. Factors such as shear damage evolution, asperity angles, surface contact area ratio, shearing rate, shear stiffness degradation, and scale effects are investigated to highlight the difference in the shear behavior of rock joints. Furthermore, roughness degradation of rock joints and the modified safety factor for the rock slope considering uncertainties are discussed in detail.</p>