Flow amplification from cascading landslide dam failures: Insights from flume experiments

Abstract

The 2008 Wenchuan Earthquake triggered numerous co-seismic landslides, and formed many landslide dams. Debris flows or floods during intense rainfall can cause the sequential collapse of those landslide dams. There is an amplification effect of the cascading landslide dam failures, which increases the magnitudes of debris flows or floods. Runs of flume experiments with different initial conditions were conducted to study the scale amplification effect. Among them, a large-scale flume experiment was performed to reduce the size effect of the miniaturized physical experiments to some extent. Experimental data such as the flow discharge, pore pressures, and microseismic and acoustic signals were used to investigate the dam failure processes and to quantify the amplification scale. The experimental results show that channel gradients and dam-failure patterns have significantly influences on the amplification effect. The intrinsic mechanism of the amplification effect can be interpreted from the perspective of energy, which is a progressive storage of potential energy and subsequent rapid release of the energy. Steep channel gradients imply greater potential energy and lower stability of the landslide dam. The sudden dam collapse related to internal pore pressure evolution will lead to rapid release of the accumulated potential energy to downstream, and cause a maximum instantaneous dam-break discharge. Experimental results show that the peak dam-break discharge caused by sudden failure can be 2–3 times that of overtopping, which should be fully considered to avoid underestimating the scale of the potential catastrophe.