A Soil Erosion Testing Device for Measuring Critical Shear Stress and Erosion Rate

Soil erosion characteristics in embankment dam materials play a crucial role in the evolution of breach morphology because of overtopping-induced dam failure. This study develops a testing technology that directly measures the shear stress at the water-soil interface by detecting the microstrain in the soil. Consequently, a soil erosion testing device (SETD) is designed to directly measure both the critical shear stress necessary for soil erosion initiation and the erosion rate. The SETD includes a hydrodynamic system, a soil erosion system, and a data acquisition system. The hydrodynamic system continuously observes the flow velocity adjacent to the soil sample. In contrast, a sample lifting component monitors the erosion progress in real time, maintaining a consistent height at the water contact point to ensure uninterrupted erosion. The erosion system utilizes a shear stress measurement component to measure the flow shear stress at the water-soil interface directly, and the data acquisition system automatically logs both the flow shear stress and the erosion rate of the soil sample. The validation experiments demonstrate a linear correlation between the erosion rate of cohesive soils and flow shear stress. The critical shear stress for initiating erosion increases significantly with higher compaction levels and clay content. For noncohesive soils, the experiments have established a distinct linear correlation between critical shear stress and median grain size on a double-logarithmic scale, underscoring the impact of particle size on erosion characteristics. Based on the experimental data presented in this study, a predictive model was developed for the critical shear stress and erosion coefficient of cohesive soils. Results indicated that by optimizing model parameters and incorporating more soil-related characteristics, the model effectively captured the relationship between critical shear stress, erosion coefficient, and soil properties. This provides a scientific basis for selecting erosion parameters of dam materials in dam breach simulations.