Physical Model Experimental Study on Landslide-Generated Impulse Waves: A Case of Near-Dam Reservoir Landslide on the Upper Yellow River of China

Reservoir-bank landslides may become unstable after reservoir impoundment and generate impulse waves, posing serious threats to hydropower hub structures, reservoir navigation, and downstream safety. The H1 landslide, with a volume of approximately 5.35 million m3, is located on the left bank of the near-dam reservoir area of Yangqu Hydropower Station. Reservoir operation and water-level fluctuations may affect the stability of the H1 landslide; if instability occurs, rapid water entry could generate impulse waves that threaten the hydraulic structures. To evaluate the impulse-wave hazards associated with the H1 landslide, a three-dimensional physical model was constructed at a geometric scale of 1:200. Representative experiments were conducted under landslide instability volumes of 100 × 104, 200 × 104, and 500 × 104, reservoir water levels of 2710.0 m and 2715.0 m, and the corresponding prototype-oriented water-entry conditions. The generation, propagation, opposite-bank run-up, and wave responses in front of the hydraulic structures were investigated. The results show that both the initial wave height near the water-entry point and the wave height in front of the hydraulic structures increase with increasing landslide volume. At the water-entry point, the maximum wave height increases from 3.10–3.27 m for the 100 × 104 m3 landslide to 4.50–4.64 m for the 200 × 104 m3 landslide and further to 7.18–7.21 m for the 500 × 104 m3 landslide. In front of the hydraulic structures, the maximum wave height at the spillway reaches 5.61 m for the 200 × 104 m3 landslide under the ecological restricted water level of 2710 m. After superposition with the wind-wave run-up, the corresponding total wave elevation is 2718.8 m, which remains below both the dam crest elevation of 2721.0 m and the wave-wall crest elevation of 2722.2 m. However, under the normal pool level of 2715 m, the total wave elevations at the spillway and power station intake after superposition with wind-wave run-up exceed the wave-wall crest elevation, indicating a potential overtopping risk. The research results provide a scientific basis for reservoir impoundment scheduling, landslide-generated impulse wave risk prevention, and the safety protection of key hydraulic structures at Yangqu Hydropower Station.