<p>The impact of bedrock disintegration in source areas constitutes a critical internal factor contributing to the instability and deformation of granular slopes. This study analyzes granular slopes along the Duku Highway to identify susceptibility zones and develops a "V"-shaped experimental apparatus based on a representative slope profile. Through physical accumulation experiments and complementary numerical simulations, we investigated how orifice diameter, material release height, and batch supply mass affect slope development and deformation during source material impact on pre-existing accumulation slopes. Results indicate that during slope formation, particle size distribution exhibits pronounced spatial sorting patterns both on the surface and within the slope mass. The overall particle velocity and deformation magnitude increase with greater material release height and batch supply mass, simultaneously extending the duration of particle movement. Larger orifice diameters expand the affected slope area, while smaller orifice diameters tend to trigger localized instabilities, producing characteristic bimodal velocity distributions. Numerical simulations reveal that the maximum disturbance ratio of the slope mass consistently occurs under conditions of high batch supply mass, with this effect being significantly enhanced as release height increases. Additionally, high batch supply mass stabilizes the spatial distribution of the disturbance ratio, while low batch supply mass triggers pronounced fluctuating patterns. Based on these findings, this study seeks to offer a novel theoretical framework for quantitatively elucidating the deformation mechanisms of granular slopes under the influence of material supply.</p>