Influence of material characteristics on the failure mode and process of landslide dam

Landslide dams, as frequent natural hazards, pose significant risks to human lives, property, and ecological environments. The grading characteristics and density of dam materials play a crucial role in determining the stability of landslide dams and the potential for dam breaches. To explore the failure mechanisms and evolutionary processes of landslide dams with varying soil properties, this study conducted a series of flume experiments, considering different grain compositions and material densities. The results demonstrated that grading characteristics significantly influence landslide dam stability, affecting failure patterns, breach processes, and final breach morphologies. Fine-graded materials exhibited a sequence of surface erosion, head-cut erosion, and subsequent surface erosion during the breach process, while well-graded materials typically experienced head-cut erosion followed by surface erosion. In coarse-graded dams, the high permeability of coarse particles allowed the dam to remain stable, as inflows matched outflows. The dam breach model experiments also showed that increasing material density effectively delayed the breach and reduced peak breach flow discharge. Furthermore, higher fine particle content led to a reduction in the residual dam height and the base slope of the final breach profile, although the relationship between peak breach discharge and the content of fine and coarse particles was nonlinear. To better understand breach morphology evolution under different soil characteristics and hydraulic conditions, three key points were identified—erosion point, control point, and scouring point. This study, by examining the evolution of failure patterns, breach processes, and breach flow discharges under various grading and density conditions, offers valuable insights into the mechanisms behind landslide dam failures.