<p>Understanding the failure and movement mechanisms of block-type rock slopes is crucial for reliable hazard assessment and mitigation. This study combines physical experiments and numerical simulations to investigate the instability and dynamic behavior of discontinuous slopes using the discontinuous deformation analysis (DDA) method. A laboratory platform equipped with a binocular high-speed imaging system was developed to capture the complete motion process of block sliding, toppling, and collision. Comparative analyses demonstrate that DDA accurately reproduces the experimental kinematics, showing strong agreement in displacement and velocity evolution, and confirming its capability to simulate discontinuous deformation and contact dynamics. The validated DDA model was applied to the Luoma slope along National Highway G318, where a landslide impacted a downstream dangerous rock mass. Simulation results are consistent with field monitoring data, verifying the rationality of the model parameters and physical assumptions. The interaction between the landslide and the dangerous rock mass induced a coupled sliding–toppling failure with high velocity and long runout. When the dangerous rock mass was modeled as intact, it acted as a rigid barrier that effectively attenuated the landslide’s energy and limited its runout distance. The findings provide a scientific basis for quantitative assessment and mitigation of landslide and rockfall hazards in mountainous regions.</p>