Tangjiaxi Landslide and Impulse Wave Analysis in Zhexi Reservoir of China by Granular Flow Coupling Model

Abstract. Rocky granular flow usually forms after rocky bank slopes are failed and rushes into rivers at a high velocity, causing impulse wave disasters. Currently, the granular mass/water coupling study is an important trend in the field of landslide-induced impulse wave. In the paper, a full coupling numerical model for landslide-induced impulse wave is built based on non-coherent granular flow equation. In this model, Mih equation for continuous non-coherent granular flow controls the movement of sliding mass, two-phase flow equation regulates the interaction between sliding mass and water, Re-Normalisation Group (RNG) turbulence model governs the movement of water body. Taking Tangjiaxi landslide as an example, which is located at Zhexi Reservoir in Hunan Province, China, the motion characteristics of Tangjiaxi landslide and the following impulse wave process were analyzed by the coupling model, and the validity of this model was checked. On July 16, 2014, rocky blocks debris flow was formed after the failure of Tangjiaxi landslide, damming Tangjiaxi stream and thus causing an impulse wave disaster with which left three persons dead and nine persons missing. The full coupling numerical analysis showed that after the failure of Tangjiaxi rockslide, rocky granular flows impacted the water at the maximum velocity of about 22.5 m/s, with waves propagating at the maximum celerity of up to 12 m/s. The deposited topographic modeled is similar to that accumulated in the actual situation. The maximum run-up calculated is 21.8 m, close to the value of 22.7 m obtained in the field survey. A series of run-up values in the field survey matches well with the calculated values. Therefore, the full coupling numerical model built in this study can be used to simulate impulse waves generated by rocky granular flows.