Abstract:The high-speed and long run-out landslide debris flow is characterized by high kinetic energy and long moving distance, which is a kind of geological disaster with a wide range of damage and great destructive power and leads to enormous loss to human beings. Numerical simulation provides an important method to study the effects. In this paper, the numerical manifold method was used to simulate the movement process of high-speed and long run-out landslide debris flow induced by strong earthquake in Niuquangou, China. The accumulation state and movement characteristics of the landslide debris flow were studied through a series of numerical tests. The effects of vegetation coverage, spatial characteristics of retaining-wall on the accumulation state of debris flow were studied, and the disaster reduction effects of retaining-wall was evaluated. The simulation results showed that the effects of increasing vegetation coverage on the landslide movement path was limited. In order to intercept landslide debris flow better, the retaining-wall should be arranged on the motion path to effectively reduce moving distance and long-distance accumulation of debris flow. When the retaining-wall was placed in different positions, it would have different effect on the landslide debris flow, and the optimal position of the retaining-wall was determined. In addition, compared with effects of increasing the height of the retaining-wall, the multiple rows of retaining-wall structure can more effectively intercept the debris flow and reduce its harm to the downstream.