Research On Dynamic Process Of Landslide Inrush Wave Based On CFD-DEM Fluid-solid Coupling

The landslide located around the river and the bank of the reservoir,once sliding,will lead to landslide into the water and cause a huge surge,which poses a great threat to people ’ s lives and property safety.Therefore,it is of great practical significance to study the change of landslide into the water and the propagation process of surge.However,due to the landslide water inrush disaster is a process of solid-liquid-gas three-phase medium interaction,and the space and time scale are large,the traditional single medium model cannot be solved accurately.To this end,based on the computational fluid dynamics method and discrete element method,comprehensively constructs a set of solid-liquid-gas three-phase coupling model based on CFD-DEM by embedding VOF model to consider the change of solid-liquid-gas three-phase,so as to carry out the research on the dynamic process of landslide water inrush disaster.After the accuracy of the coupling model is verified by three classical experiments,it is applied to the flood disaster of large-scale real terrain landslide in mountainous areas,which provides a scientific basis for disaster prevention and mitigation in mountainous areas.The main research results are as follows:(1)Reveal the applicability of computational fluid dynamics and discrete element method in coupled model of landslide water inrushTaking the flume experiment and Daanshan rockslide as the research objects,combined with the control equations of computational fluid dynamics method and discrete element method,the characteristics of the two calculation methods in the simulation of geological disasters and the applicability of the two calculation methods in the coupling model of landslide inflow and surge are explored.The results show that the computational fluid dynamics method has good accuracy and applicability in the calculation of the wave propagation dynamic process of landslide water inrush disaster.The accuracy of discrete element method for Daanshan rockslide sliding calculation is82.41%,which can flexibly study the dynamic process of landslide sliding and water inflow.It is proved that the two methods can be effectively applied to the study of landslide water inrush disaster.(2)Programming the fluid-solid coupling model based on CFD-DEMIn view of the current research status of multiphase medium model,based on the opensource CFD software Open FOAM and opensource DEM software LIGGGHTS,the VOF model is embedded,and the interaction between solid,liquid and gas is considered.The C++ programming language is used to construct the fluid-solid coupling model based on CFD-DEM to realize the efficient transmission of information between fluid and solid.The coupling model is verified by three classical experiments,namely,single particle motion experiment,underwater particle flow experiment and Lituya Bay reduction experiment.The results prove the efficiency and accuracy of the coupling model,which provides a tool for the numerical simulation of landslide water inrush disaster.In the calculation of single particle settlement,the sensitivity of the mesh is analyzed.The results show that the coupling model can effectively reduce the error under the condition of ensuring the calculation efficiency when the mesh and particle diameter ratio is 5:1.(3)Application of real terrain landslide flood disaster-Chongqing Hongyanzi landslideHongyanzi landslide in Wushan County,Chongqing is selected as the research object.Combined with topographic data and geotechnical parameters,the coupling model is used to simulate and analyze the sliding process and surge propagation process of Hongyanzi landslide.The results show that the landslide body slides into the water about 16 s and causes about 5.69 m high surge,which is consistent with the field survey results.The surge height of Wushan wharf and the maximum distribution of surge in the basin are analyzed.The results show that the maximum surge of Wushan wharf reaches 5.19 m,which will pose a major threat to the safety of people’s lives and property near the wharf.The fluid-solid coupling model based on CFD-DEM overcomes the disadvantages of single medium model which is difficult to calculate the fluid-solid coupling geological phenomenon to a certain extent,improves the reliability and applicability of the calculation,and provides a new method and basis for the calculation of large-scale landslide water inrush disasters in mountainous areas.