Physical simulation experiment for raindrop splash erosion characteristics of shallow loess in hilly and gully region of Yan'an

Rainfall is an important factor that induces erosion and deformation damage on the slope surface in loess gully area. Taking the primary loess in Yan'an area as the research object, using the self-designed physical simulation test platform of normal-head single-droplet soil spallation, we systematically study the evolution of spallation of primary loess under different rainfall characteristics, soil water content and surface slope conditions. The experimental results show that the spattering depth increases exponentially with the rainfall duration, and the maximum spattering depth, spattering volume and raindrop frequency show linear and exponential growth, respectively. The influence of raindrop diameter and drop height on soil spallation deformation is more significant, and the soil is more prone to spallation damage under small rainfall intensity and large rainfall intensity. The soil is more susceptible to spallation damage in the case of small rainfall with high moisture content and large rainfall with low moisture content. The maximum spallation depth decreased linearly with the surface slope, while the spallation volume decreased and then increased with the surface slope. Based on the experimental results, an empirical expression for predicting the characteristic indexes of raindrop spallation of in-situ loess was proposed.