Stability analysis of landslide dams under surge action based on large-scale flume experiments

Abstract

In recent years, large magnitude earthquakes have caused the formation of a large number of landslide dams. The rising water level in the landslide lakes may induce a large number of landslides in the lake areas. When landslides rush into a lake area, large-scale surges may be produced and would then strongly impact on the dam stability and cause a breaching process. To understand the erosion failure modes of dam bodies caused by surges and the variation in the pore water pressure in the dam body, large-scale wave flume tests were carried out in this study. Six groups of comparative tests were carried out to study the two main influencing factors, namely, the upstream water level and the wave height. It was found that (1) when subjected to surge waves, the landslide dam stability is determined by the difference (ΔH) between the effective water level (the sum of the water level and the overlapping wave height) and the effective dam height (the dam height after lowering due to local sliding); (2) when ΔH < 0, overtopping does not occur, and the landslide dam remains stable. A stable upstream erosion surface eventually forms, the surface slope angle decreases and the erosion volume increases as the wave height increases; when ΔH > 0, the dam is overtopped and breached by the next waves; (3) During dam breach by overtopping with surge waves, the erosion in the breach initiation phase is much faster than by overtopping without surge waves, but the difference in the breaching development phase is not very significant; and (4) the pore water pressure close to the upstream slope is much more sensitive to the action of the surge waves than deeper inside the dam body.