Influence of reservoir water level variations on slope stability and evaluation of landslide tsunami

Reservoir filling and water level variations are important factors that induce slope failures near the reservoir banks. Once a landslide occurs, a tsunami might form which can result in a far greater disaster. This study provides insight and a method for analyzing the disaster chain of a landslide near the reservoir water by taking a slope near the bank of A’lagou reservoir in Xinjiang, China, as an example. The instability mechanisms of the slope are studied based on the field investigation and numerical analysis. The results show that there are two factors that increase the process of slope instability: the rock structure of the slope, which is an important internal factor, and the reservoir filling, especially the rapid drawdown which is an important external factor. Then, a numerical simulation that is based on SPH-DEM coupling method is used to evaluate the landslide tsunami process. The quantitative analysis of the tsunami indicates the initial wave height is about 22 m, the tsunami run-up on the opposite slope is about 44 m high, the maximum overtopping flow is about 1.35×10⁴ m³/s, the maximum velocity is about 9 m/s, the maximum overtopping depth is about 7 m, and the erosive velocity on the downstream slope of the dam is > 20m/s. The results of this study will be useful for preventing and mitigating landslide hazards in reservoirs.