DAM Break Simulation And Flood Risk Research Of Earth-Rock Dam

Dam break has the characteristics of low probability and high risk.Once the dam breaks,it will cause a great threat to the life and property safety of the downstream people.Dam break flood risk assessment is an important non engineering measure in flood control and disaster reduction system.The most effective way to study dam break flood risk is to simulate dam break flood.Because of the complexity of earth rock dam break process,the regional difference of dam break flood evolution process,and the difficulty of flood risk assessment,the research on dam break flood risk has always been a hot and difficult point in academic and engineering circles.In view of this,this paper takes Chengbihe reservoir in Guangxi as the research object,uses HEC-RAS model to simulate dam break and flood evolution,uses the disaster system theory to analyze the dam break flood risk in the downstream Baise City.The main research work and achievements are as follows.(1)The HEC-RAS dam break model is used to simulate the process of earth-rock dam break under 13 schemes,and the influence of break mode on the flow process and water level process of earth-rock dam break is analyzed.The results show that the final bottom elevation,dam break duration and starting elevation of the breach have an effect on the discharge and water level process of the breach.The higher the final bottom elevation of the breach is,the smaller the peak discharge of the breach is;the longer the breach lasts,the flatter the breach discharge process is,and the smaller the peak discharge is;the elevation of the starting breach water level has relatively small impact on the breach discharge process and water level process.(2)Based on the boundary conditions of the four schemes of total breach,1/2 breach,1/3breach and breach lasting for 8 hours,the one-dimensional HEC-RAS model is used to simulate the evolution of dam break flood.The results show that: the time of flood front and flood peak reaching the downstream increases with the decrease of dam break degree and theincrease of dam break duration;the smaller the dam break degree is,the smaller the peak discharge is,and the lower the corresponding flood decay rate is;from the dam site section to the Tianzhou hydrological station section,the peak discharge decay rate of the four schemes is78%,77%,67% and 45% respectively.(3)Based on the flow hydrograph of total breach,1/2 breach and 1/3 breach,the two-dimensional model HEC-RAS is used to simulate the evolution of dam break flood.The results show that the inundation process of dam break flood in the three schemes is similar to that in the downstream Baise City,but the inundation degree is different.the inundation range,inundation depth,inundation velocity and inundation duration increase with the increase of dam breach degree.The maximum error of water balance of the three schemes is 4.85%,which meets the requirement of water balance.(4)Based on the results of two-dimensional simulation and the theory of disaster system,the risk assessment of dam break flood in Baise city is carried out.The results show that:under the condition of total breach,1/2 breach and 1/3 breach,the proportion of low-risk areas in Longjing street,Baicheng street and Yongle Town increases with the decrease of breach degree,the proportion of high-risk areas decreases with the decrease of breach degree,while the proportion of medium risk areas varies with each other;under the condition of total breach,the proportion of medium and high-risk areas in the study area is mainly 50.24% and 35.96%respectively,which are mainly concentrated in the study area Longjing street.The results show that the risk of dam break flood to Baise city is high,which can provide scientific basis and theoretical guidance for relevant departments to formulate flood control and disaster reduction plans.