Overtopping of embankment dams from landslide generated waves
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A landslide entering a reservoir transforms its kinetic energy into an impulse wave. This wave propagates across the basin, runs up the shores and may overtop the dam. The consequences of such event are damages to nature and infrastructure, as well as a risk of human life losses. Due to their topographies, this danger threatens both Norway and the Alps areas: reservoirs, lakes or fjords are often located below steep shores with potentially unstable sliding masses. This thesis is a parametrical study on landslide generated impulse waves, based on experiments conducted in a laboratory on a 1:190 scale model. The landslide is simulated by blocks sliding down a ramp on the reservoirs sides, entering the water, creating a wave running up on the opposite shore and propagating towards the dam. The resulting overtopping is thereby also influenced by the run-up waves along the lake shore. The primary objective of this thesis is to use the scale model to investigate the overtopping of embankment dams due to landslide generated impulse waves. In order to better understand the parameters influencing the overtopping volume, height and discharge, different parameters were varied over the tests. Dam roughness, dam upstream slope, freeboard, landslide volume, shape and impact velocity were investigated, as well as the influence of a wave wall integrated into the upper part of the dam. Furthermore, overtopping speed and discharge, plus wave generation and propagation pattern were observed and described. The lateral position of the landslide in the reservoir has caused a complex wave reflection phenomenon resulting in an uneven overtopping along the dam crest. The results of the tests indicate a major influence of the freeboard on the dam overtopping as well as, an additional impact of landslide volume on the overtopping volume, and landslide length on the overtopping height. The best way to mitigate the hazard is therefore by lowering the water level in the reservoir. Additionally, the implementation of a vertical wave wall has also shown to have an influence on the overtopping volume and needs to be further analysed. Finally, it is observed that the lateral landslide model makes it harder to apply impulse wave equations established in flume or wave basin.