Experimental Investigation on the Breaching Mechanisms of Landslide Dams with Heterogeneous Structures

Landslide dams are natural dams formed by river blockages with high speeds caused by landslides, collapses, and so on. Dam failures pose great threats to people and infrastructure upstream and downstream. A deep understanding of the influence of heterogeneous structures on dam breaching can provide an important scientific basis for the risk assessment and emergency treatments of landslide dams. In this study, laboratory physical modeling tests were conducted to investigate the effects of homogeneous, vertical heterogeneous, and horizontal heterogeneous structures on the breaching process. The experimental results showed that: 1) The erosion process of landslide dams was significantly affected by the material properties of the local location. 2) For the homogeneous dams, when the median diameter of materials increased, the breaching character- istics would change from laminar scouring to scarp erosion, then to multistage scarp erosion, the peak discharge would decrease, and the peak arrival time would be delayed. 3) For the vertical heterogeneous dams, the upper material mainly affected the duration and the upstream water level of the breach initiation stage; the middle material mainly affected the vertical erosion rate in the breach development stage; the bottom material mainly affected the stability of the downstream slope and the geometry of residual dam. The material distribution of the middle and bottom layers had the most significant effect on the peak discharge, because of the positive interaction between the breach deepening and the outflow accelerating. 4) For the horizontal heterogeneous dams, the upper material on the overflow side affected the initial vertical erosion rate; the bottom material on the overflow side and the upper material on the opposite side affected the subsequent vertical and lateral erosion rates, respectively; the influence of the bottom material on the opposite side was minimum. When designing the discharge channel, the influence of heterogeneous structures should be considered. Engineering measures should be adopted to restrict the breach deepening and promote the breach widening to minimize the peak discharge. © 2023 Editorial Department of Journal of Sichuan University. All rights reserved.