Experimental Investigation of The Scouring of Quake Dams During Dam-break

Earthquake can trigger debris flow that can result in formation of quake lakes. The break-up of the quake dams can lead to catastrophic flooding for residents living in lower reaches of the rivers. By using high-speed photography, a set of laboratory tests were conducted to study the processes of downward erosion, head cutting erosion, and the characteristics of dam-break flows with different dam configurations. Experimental observations indicated that the quake dam's evolution was a gradual process during dam failure. In cases wherein flow took place without a discharging channel, head cutting appeared in every test, with the downstream edge of the eroding crest retreating upstream. As flood water overtopped the dam, knick points appeared and moved upstream. The case of flow through a discharging channel with small dam seepage was then studied. It was observed that the bottom erosion leads to a head cutting process in the longitudinal direction, while both sides of the discharge channel collapse gradually into the channel. The alluvial fan enlarges and extends sideway and forward continuously. Finally, the case of flow with a discharging channel and large dam seepage was studied. For this case, the breach development process was similar to that when discharging through a discharging channel with small dam seepage. In addition, cross-sectional depression and slope-break points developed during the scouring process. The discharge channel finally extended to both sides of the flume, with the upstream part deepening and forming a channel with an irregular shape. The amount of post-discharge residual debris of three cases was also measured. After 200 s of the discharging, the model in which flow occurred without discharging channel left behind the smallest amount of residual debris. On the other hand, flow through a discharging channel with large dam seepage led to the largest amount of residual debris. The findings from the experiments can provide useful reference for mitigating the risk of potential dam-break from quake lakes.