Experimental study on the river blockage and landslide dam formation induced by rock slides

Abstract

Rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels, resulting in a significant impact on the continuity of mountainous rivers. Based on the extent of blocking, the blockage type is divided into three categories in this paper: no blockage (submerged dam), partial blockage, and complete blockage. The accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams. In this study, rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides, and the factors that dictate the formation of landslide dams are critically analyzed. The experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition. In addition, the less fragmented rocks result in larger maximum deposit height (maxi-DH) and smaller minimum deposit height (mini-DH), while the better fragmented rocks result in smaller maxi-DH and larger mini-DH. Furthermore, the water depth has a significant impact on the river blockage type. A new Blockage Index (BI) that combines the landslide volume and the wet cross-sectional area is proposed to assess the damming capacity of rock slides. Then a method for predicting the river blockage type of rock slides is developed based on the relationship between Blockage Index and the ratio of maxi-DH or mini-DH and water depth. The model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future.