The erosion-entrainment process of landslides involves disturbance and incorporation of basal materials by the sliding body during motion, driving a rapid increase in landslide volume. This process is especially pronounced in long-runout landslides with high-altitude, where high-energy sliding body strongly impacts the basal surface. However, limited experimental conditions constrain the understanding of the internal dynamic behavior during impact. To address this, 51 large-scale flume experiments were conducted, varying in sliding body type (characterized by different particle sizes), mass, velocity, and deposition layer thickness. Particle image velocimetry (PIV) was used to quantify erosion modes, while normal stress sensors recorded basal stress responses. The dynamic coefficient k_d was used to evaluate the dynamic behavior of impact process. Results reveal two distinct erosion phases: an initial impact-induced erosion stage associated with peak basal normal stress, followed by motion-induced erosion. During the impact-induced erosion stage, k_d increases with mass and velocity, but decreases with deposition layer thickness. k_d increases with particle size under low mass conditions, but decreases when the mass is high. In addition, a linear relationship between k_d and the initial momentum p of the sliding body was established. The negative effects of particle size and deposition layer thickness on the linear relationship were preliminarily identified. In summary, this study provides a reference framework for future laboratory investigations into the internal mechanical responses of deposition layers during impact-induced erosion caused by landslides.

Experimental investigation,Impact-induced erosion,Dynamic coefficient,Long-runout landslides with high-altitude