Experimental investigation on the erosion characteristics of landslide dam failure induced by overtopping

This study addresses the limitation of laboratory tests with underestimated storage capacities by conducting experiments on the breach failure of landslide dams with larger storage capacities. The erosion characteristics and evolution patterns of the breach were observed and analyzed. The research identifies three stages in the erosion process: the initial stage, accelerated erosion stage, and decelerated erosion stage, each exhibiting distinct hydraulic and erosion characteristics. Notably, the initial stage displays 'local drop' type headwater erosion, the accelerated erosion stage features high-speed downward erosion across the entire section, and the decelerated erosion stage is marked by erosion in the upstream and sedimentation in the downstream. The study suggests that small storage capacities in previous experiments may contribute to the failure in simulating the characteristic decelerated erosion stage. Peak erosion rate occurs during the accelerated erosion stage, and peak discharge follows afterward. The downstream surface slope of the landslide dam varies continuously during the initial and decelerated erosion stages, while it increases and then decreases during the accelerated erosion stage. The dam crest slope increases in the initial stage and decreases in both the accelerated and decelerated erosion stages. Upstream inflow significantly affects the duration of the initial stage, with a smaller impact on the accelerated and decelerated erosion stages. Materials with strong local erosion resistance in the spillway hinder headwater erosion during the initial stage, influencing its duration. These findings provide valuable insights into the breach failure mechanism of landslide dams and contribute to flood control and disaster reduction efforts.