Interactive effect of soil dispersity and rainfall intensity on splash erosion: Insights from laboratory tests

Dispersive soil is a common problematic soil that segregates in water, resulting in instability of slopes and posing significant threats to the safety of earth structures. However, there is a limited amount of research on the hydraulic erosion of dispersive soil. Splash erosion is the initial stage of hydraulic erosion. A clear understanding of splash erosion is crucial for investigating dispersive soil hydraulic erosion. This study explored the influence of soil dispersity and rainfall intensity on the characteristics of splash erosion by conducting consecutive single-drop rainfall tests on artificially prepared non-dispersive and dispersive soil samples with varying sodium carbonate content. High-speed cameras and single-lens reflex (SLR) cameras were used to capture the variations of the splash crown, splash pan, and splash crater. Results showed that the content of sodium carbonate significantly affected splash erosion. High soil dispersity resulted in smaller masses of splashed soil material and infiltration water, but a larger mass of splashed water. It also led to a smaller volume and depth of the splash crater. The critical value of the content of sodium carbonate for soil dispersity discrimination was 0.15 %, the same as the threshold for the splash process to stop significant changes. The shape of the splash crown also helped analyze the process of splash erosion and was relevant to the splash crater shape. Increasing soil dispersity diminished the impact of rainfall intensity on splash erosion. These findings provide new comprehension of the mechanism of splash erosion of dispersive soil and lay a foundation for the systematic study of hydraulic erosion of dispersive soil in engineering slopes.