Predisposing factors and hydrodynamic conditions controlling the failure of earth dams by overtopping based on physical modeling experiments

Dam landslides occurred frequently during recent years, and the secondary disasters caused by it can cause great harm to local resident in an extensive area. Therefore, it is important to understand the mechanisms of dam failure. Experiments were designed to study the mechanisms of dam failure, analyze the effects of multi-factors, and establish a method for the critical condition of dam breach. The results showed that before the collapse, the existence of the notch surface accelerates infiltration and causes advancement of the speed of the wet front. The dam failure process can be divided into three stages: erosion initiation, erosion acceleration, and erosion weakening. During the breaching, three important erosion phenomena were observed including slope instability, steep slope, and collapse. Based on statistical analyses of the changes in the longitudinal slope profile and erosion rates observed during the dam failure, characteristics of erosion rate along the longitudinal profile have been summarized well. The slope of the bottom groove, size of the dam body, upstream inflow discharge, and median particle size of the dam body significantly affected the characteristics of the dam body collapse. Then, a critical water head that leads to an overtopping outburst was established based on the experimental data and theory of incipient motion of sediment, providing critical information to predict dam failure. The results of this research would be helpful to predict the disaster chain and enhance the risk management of this kind of disaster chain.