<p>This study introduces a rough interface construction method that considers the morphology of surrounding rock in mining stopes, applied to backfill-rock samples and numerical models. Using a smooth-joint model in the PFC3D numerical software, accurate contact conditions were achieved at the backfill-rock interface. This approach overcomes the limitations of simplified geometries in capturing the influence of rock morphology on shear behavior. Comparative analysis between experimental and simulation results showed that increasing cement content and normal stress enhances the shear strength of backfill-rock samples. Increased normal stress promoted microcrack propagation in concave regions of rough surfaces, strengthening failure resistance by improving backfill sliding resistance. Conversely, decreased cement content led to rapid microcrack development along mold edges, suggesting that lower cement content reduces shear resistance and influences failure characteristics. The PFC3D simulations successfully replicated stress responses and failure patterns observed in experiments, providing a robust framework for investigating the mechanical behavior and failure mechanisms of backfill-rock interactions. These insights provide a valuable basis for optimizing backfill-rock stability and improving underground mining safety and efficiency.</p>