Mechanisms of sidewall collapse in fine gullies due to water erosion

Abstract

The collapse of fine gully sidewalls significantly exacerbates soil erosion; however, the processes and mechanisms driving these collapses remain insufficiently studied. In this study, we developed a specialized slope erosion test system to examine fine gully sidewall collapses across varying slope angles, water head heights, and sidewall heights. Using 3D reconstruction, fixed grid coordinates, polyethylene trajectory tracing, and direct shear testing, we systematically captured and analyzed the collapse dynamics of fine gully sidewalls. Key findings indicate that capillary action and scouring contribute distinctly to the varied collapse morphology of fine gully sidewalls. Based on collapse test results, we derived an expression to characterize the soil moisture field, and using direct shear test data, we formulated an expression for the soil friction angle under varying moisture conditions. Further theoretical derivation yielded a method for accurately calculating the top crack location and critical collapse state. The findings presented herein establish a theoretical foundation essential for advancing erosion control strategies and preventive measures.