Physical Mechanism and Numerical Simulation of Landslide Dam Formation

Abstract

AbstractLandslide dam formation creates one of the most hazardous geomorphic phenomena, which often threaten the safety of upstream and downstream communities by causing various secondary hazards, such as backwater inundation, dam breaches, debris flows, and outburst floods. Understanding the conditions and processes of the landslide dam formation is useful for hazard assessment and its disaster countermeasures. This research presents the physical mechanism of landslide dams and their entire formation process through three typical cases, namely the large-scale Kuridaira and Akatani landslide dams in Nara prefecture, Japan and the massive Jure landslide dam in Sindhupalchok district, Nepal, by using ring shear tests and integrated simulation with LS-RAPID model. The results from ring shear tests show that the samples of the sliding surfaces underwent substantial grain crushing and sliding-surface liquefaction due to a rapid generation of pore water pressure and significant loss of shear strength. In the computer model, the formation processes of the three landslide dams consisted of four main stages from stable slopes to local failures through progressive failures to massive slope movement at high speeds and river damming at the end of the motion. The analysis indicates the high mobility behavior that governs the rapid motion of the landslides is a primary contributing factor to the dam formation.