Review and Prospect of the Formation Mechanism of Landslide Dams Caused by Landslide and Avalanche Debris

Landslide dams are natural dams, which are formed where rivers are blocked by avalanches, landslides, and debris flows. China is a high incidence area of landslide dam disasters. According to the statistics, among the cases of landslide dam in the world, 758 cases occurred in China, accounting for 59%. In recent years, frequent geological tectonic activities and extreme climate disasters (typhoons, rainstorms, snow melting, etc.) have induced a large number of landslide dams, which significantly threaten the lives and properties of upstream and downstream people. The landslide dams caused by landslide or avalanche debris normally have loose structure, poor stability, high breach size and fast breaching velocity, leading to huge breaching flood and catastrophic disaster to the downstream areas. This paper first briefly reviewed the blocking studies of generic landslide dam, and clarified the formation characteristics of landslide dam caused by avalanche and debris. Then, the movement and fragmentation mechanism of debris body and the blocking mechanism of debris body were analyzed, the characteristics of particle separation and accumulation in the process of dam formation were specifically summarized. On this basis, the effects of particle fragmentation and geological conditions on the morphological characteristics, material compositions and dam stability were confirmed with less previous studies. There were usually three dam-forming modes: sliding type, climbing type and reentry type. There were significant differences in the stabilities of different types of dams. The stability of landslide dams was closely related to the dam characteristics (geometric shape, dam structure and material composition) which were jointly determined by the debris colliding and disintegrating during sliding and solid-liquid coupled interacting during debris rushing into river. A research idea was put forward to reveal the internal relationships between the influencing factors of dam formation and the spatial shape, structural characteristics and stability of dams, so as to establish a prediction model of dam characteristics based on the rapid evaluation of dam stability. This research was meaningful in both academic and practical phases to predict the key parameters of landslide dams before its formation, and rapidly assess the landslide dam stability after its formation. © 2020, Editorial Department of Advanced Engineering Sciences. All right reserved.