Numerical Simulation Of Debris Flow Characteristics And Movement Process In Baishitougou Of A Power Station

With the rapid development of the Belt and Road construction,various infrastructure such as highways,Bridges and water conservancy projects gradually incline to the western mountainous area,and debris flow disaster in the mountainous area is often a major threat to the development and construction.As one of the common natural disasters in mountainous areas,debris flow is characterized by uncertainty,high risk and short duration,which often brings great losses and injuries to people’s production and life.Wuhai pumped storage power station is an important hydraulic engineering hub located in the mountainous area of complex terrain.The frequent occurrence of debris flow in Baishitougou in the upper and lower reservoirs poses a huge security threat.Therefore,it is of great practical significance to study the developmental and kinematic characteristics of debris flow to provide a basis for the design of debris flow control engineering.In this paper,the main gully of Baishitougou is taken as the research object.Based on the existing data and investigation,the topographic characteristics,provenance distribution,development characteristics and dynamic characteristics of the main gully of Baishitougou are analyzed.Combined with CFD,fluid-structure coupling and other relevant theories,the three-dimensional geological model was established by numerical simulation method,and the appropriate mathematical model and parameters were selected to calculate the three-dimensional flow field of the main gully of Baishitou gully at different frequencies(10,20,50,100,200 years)with ANSYS CFX.On this basis,the proposed dam is set up,and the three-dimensional flow field results under corresponding working conditions are given and analyzed.The coupling surface data is obtained based on the numerical results of the flow field,and then the structural module in ANSYS software is used for unidirectional fluid-structure coupling analysis.The main research contents and achievements are as follows:(1)Based on the topographic conditions and watershed characteristics of Baishitougou,the development and dynamic characteristics of debris flow are analyzed and discussed.It is concluded that the debris flow in Baishitougou is a ravine type,high-frequency and rainstorm debris flow,which has obvious zoning characteristics and more unstable material sources.The dynamic characteristic parameters of debris flow such as volume density,velocity and peak discharge are given by combining relevant theoretical calculation and experimental method.(2)The theory of numerical analysis of debris flow is discussed,which mainly includes computational fluid dynamics theory and mathematical model of debris flow movement;The rheological properties,models and two-phase motion models of debris flow are analyzed and discussed.Single-phase and Bingham models are selected as mathematical models,and finite volume method is adopted for calculation.In addition,the mesh partitioning idea,mesh quality and the control of solving parameters are discussed.(3)The three-dimensional finite element model was established,and the three-dimensional flow field of debris flow in the main gully of Baishitou was analyzed with ANSYS CFX numerical simulation software at different frequencies,and the result cloud diagram of velocity and pressure was given.Analysis of motion process at different time;Velocity and pressure characteristic parameters.In addition,the analysis results of debris flow movement characteristics under different frequencies of the proposed dam are given,and the results under the action of the dam are compared and discussed.The results show that the construction of the dam is conducive to reducing the flow rate of debris flow,and the pressure of the channel increases,so that it can be silted in the upstream,which can reduce the damage to the downstream facilities.(4)Based on the flow field results,the dynamic response of the dam body under different working conditions was obtained by using Structural modules for fluid-structure coupling calculation.The dynamic characteristic parameters of total displacement,stress and strain were given,and the relationship between the characteristic parameters and the flow rate was obtained.With the increase of flow and scale of debris flow,the total displacement,strain and stress of the dam body slightly increase,and the maximum stress and strain are mainly located at the foundation and abutment of the dam,and the displacement presents an inverted arch stratification.The characteristic parameters of each dam under the same working condition are compared and analyzed,and the reasons are explained.At the same time,the dam body is judged to reach the critical value,which can provide reference for the planning and design of debris flow control engineering.The results show that the stress value of the dam body does not reach the critical value of failure under the condition of 10,20,50 and 100 years.The No.3 dam is close to the critical value of failure under the condition of once in 200 years,so measures should be taken to reduce the impact effect of debris flow.