| Debris flow is a complex multiphase fluid,which carries a large number of solid materials inside,and has a huge impact force,which often causes great casualties and property losses.Since debris flow is often sudden,it is often difficult to observe in real time.The three-dimensional numerical model of debris flow can intuitively reproduce the movement and accumulation process of debris flow when it flows through the gully.Therefore,the research of three-dimensional numerical simulation of debris flow has important theoretical significance for the prediction of damage scope of debris flow and the optimization layout of prevention and control engineering.Based on the coupled numerical methods of smooth particle fluid dynamics(SPH),discrete element method(DEM)and finite element method(FEM),the two-phase dam break simulation analysis was carried out to verify the reliability of the coupled numerical model.Taking Xiaohegou debris flow in Manyao Town,Gejiu City,Yunnan Province as a typical study area,the SPH-DEM-FEM coupled model considering the channel erosion process was proposed to analyze the movement,erosion and accumulation process of Xiaohegou debris flow.SPH-DEM-FEM coupling numerical method was used to build a fluid-structure coupling model between debris flow and arresting engineering,and on this basis,the dynamic response process of debris flow solid-liquid mixture to arresting structure was analyzed,and the prevention and control effect of arresting engineering was quantitatively evaluated.The main contents and achievements of the research are as follows:(1)Through field investigation,the geological environment and formation conditions of Xiaohegou debris flow were discussed,basic characteristic parameters of debris flow were calculated,and a prediction model of debris flow accumulation range based on geomorphic investigation method was proposed.(2)The SPH-DEM-FEM coupled numerical theory was discussed,the existing dynamic models of debris flow were summarized and analyzed,and the SPH-DEM-FEM coupled numerical model of two-phase dam break was constructed,and the numerical model was verified by previous experimental results.The results show that the time-history curve of the fluid front displacement is basically consistent with the time-history curve of the indoor physical model test.The rationality of the coupling numerical analysis method proposed in this paper for the dynamic process simulation of debris flow is demonstrated.(3)Based on SPH-DEM-FEM coupled numerical method,a three-dimensional numerical model of Xiaohegou debris flow was constructed to simulate the movement process of gully debris flow,the erosion process of gully debris flow and the accumulation process of gully debris flow.The dynamic characteristics and accumulation range of Xiaohegou debris flow were analyzed.The results showed that:The simulation results of debris flow accumulation area are in agreement with those of geomorphic survey method.The influence of structures on the accumulation range of debris flow is quantitatively analyzed.The results show that the farthest movement distance of debris flow decreases to 48m,the maximum accumulation depth increases by 1.89m,and the peak velocity decreases by 0.9m/s.(4)Based on SPH-DEM-FEM coupling numerical method,a three-dimensional fluid-structure coupling model of debris flow and arresting dam was constructed,and the impact effect of debris flow solid-liquid mixture and dynamic response characteristics of arresting dam were analyzed.The results show that the sweep area of debris flow decreases significantly,and the farthest moving distance decreases from 1.584×10~3m to 1.394×10~3m.Through the buffering and blocking effect of the barrier dam,the danger area of debris flow is reduced effectively,and the effectiveness of the control measures is revealed.Through the dynamic response analysis of the dam,the change rule of debris flow impact is obtained,and compared with the empirical formula,which can provide a certain reference for the calculation of debris flow impact force and the design of the dam. |
