Experimental and numerical study on the breaching mechanisms of landslide dams with non-uniform structures

Landslide dams often exhibit non-uniform structures due to the rapid and dynamic accumulation of various types of landslide materials. These variations in dam composition significantly impact breach progression, causing significant errors in current model tests and numerical simulations with uniform structure assumptions This adversely affects peak flow predictions and decisions related to risk prevention and control. This study conducted a series of flume tests to examine the influence of non-uniform structures on the failure mechanisms of landslide dams. A 3D dam breach model was used to replicate these flume experiments and obtain more detailed information. Large Eddy Simulation (LES) captures the hydraulic features of dam-break flow, while equilibrium equations model morphological changes in landslide dams amid complex terrains using suspended and bed load transport. The findings indicate that in a uniform dam, the presence of coarse particles shifts erosion characteristics from layered erosion to step-pool development. Furthermore, as the content of coarse particles increases, the number of steps also rises. In the vertically non-uniform structure, the upper layer affects the formation of the breach, the middle layer affects the dam break and the breach flow, and the bottom layer affects the remaining dam height. The presence of an armor layer results in a higher water level and accelerates breach formation with a larger breach flow. In the horizontally non-uniform structure, the upper part of the overflow side is the core area of the breach, the lower part of the overflow side and the upper part of the opposite side affect the downcutting and widening rates of the breach, respectively. Preferentially, the breach tends to develop towards the relatively weaker of the two sides.