Failure characteristics of landslide dams considering dam formation features in laboratory experiments

The geometries and material properties of a landslide dam depend on the dam formation process and affect the breaching process. A comprehensive understanding of the entire process of dam formation and breach is necessary for a more accurate analysis of the dam stability and failure characteristics, but little research has been done in this area. In this study, the effects of debris composition, sliding width, and valley shape on dam breaching by considering dam formation features were experimentally investigated. Results reveal that the stability and failure modes of landslide dams are predominantly governed by the debris composition. The dam stability increases with mean grain size, especially the grain size at the overflow location. Dam height and width are largely influenced by debris composition and sliding width, and the lake volume is highly dependent on the valley shape. The arrival time of peak discharge for balance-grained dams is more related to the dam height than the lake volume, while fine-grained dams are the opposite. The peak discharge is significantly influenced by the lake volume and released water volume, while the effects of dam height, downstream slope, and lake shape coefficient are negligible. Balance-grained dams exhibit two longitudinal evolution models in different shaped valleys. The evolution model of fine-grained dams is different from that of balance-grained dams and is independent of valley shape. This study improves our current understanding of the whole process of landslide dams from formation to failure and the effects of dam formation features on dam breaching.