Simulation Analysis And Impact Study Of A Dam Failure In A "head-top Reservoir" In Yunnan On Downstream Highway Facilitie

"Overhead hold" means that tail ore and sand gather at a high part to form a man-made hazard source with high potential energy.Tailings pond dam break accidents are often induced in flood season and earthquake conditions.Once the accident causes huge safety risks to important downstream facilities and personnel gathering place,it may lead to serious casualties and economic losses.Therefore,it is very necessary for important facilities and engineering construction projects to control such risks under disaster conditions.Taking an "overhead warehouse" as an example,this paper uses FLO-2D numerical simulation software to study the impact of the dam break of the "overhead warehouse" on downstream important facilities.The main research contents include the following aspects:(1)Establish the dynamic numerical model of tailings pond dam break.The rheological model and calculation method of tailings sand flow evolution law after dam break are analyzed,and the numerical simulation theory and calculation module used for sand flow evolution are determined.The relevant parameters of numerical simulation were selected and the processed measured figure was imported into 3D-mine software to establish a three-dimensional model and extract DEM data.(2)Study the impact of sand flow on downstream important facilities in the process of dam break.Through the FLO-2D numerical simulation software,the influence analysis of the evolution law of sand flow(mud flow)after the tailings pond dam break is carried out,including:sand collapse amount,submerged range,final buried depth,maximum flow depth,maximum velocity,impact force,static pressure.(3)According to the damage characteristics of pier column,build a risk analysis and evaluation model.The risk of sand flow to the pier column is assessed at different amounts of sand.First,the maximum flow depth and maximum flow velocity were used as evaluation factors to draw the risk zoning map.Secondly,the vulnerability analysis system is established through site survey and data collection.Thirdly,the risk assessment was carried out for the severity of dam break consequences.The expression model of "risk=risk ×vulnerability" was adopted to conduct risk zoning according to the risk value.Finally,according to the results of risk zoning,corresponding risk prevention and control measures are proposed.The research results are as follows:(1)Since the terrain through which the soil and sand collapse fluid flows after dam break is groove-like,relatively narrow and deep,and the drop is large(87m),the impact range is far away and the burial depth is relatively large after dam break.The results show that:according to the most unfavorable situation,the overflow range reaches about 1km,and the overflow fluid can reach the downstream highway,but will not reach the downstream village.Under the influence of terrain conditions,the impact width of the flowing fluid is small,in the range of 18m-53m.The maximum flow depth after the impact of soil and sand collapse fluid is generally between 2-6m,and the flow depth can reach 9.3m in some low-concave zones.When the fluid spout reaches highway No.2 and No.3 pile,its flow velocity reaches 3.8m/s,and then the flow velocity gradually decreases(except for the local steep section).After passing through a small pond,the flow velocity basically decreases to 0.5-2m/s,and the covering thickness(final buried depth)of the soil and sand spout fluid is 1-3m.(2)Risk analysis method and vulnerability analysis method are used for dam break risk assessment.The results show that the risk level of pier No.1 and No.6-9 is no risk,and the risk level of pier No.2-5 is low risk.Under the condition of average sand collapse amount,the risk level of pier 1,7-9 of expressway is no risk,and the risk level of pier 2-6 is low risk.Under the condition of maximum sand collapse amount,the risk level of No.1 and 7-9 piers of expressway is low risk,and the risk level of No.2 piers is medium risk.(3)According to the evaluation results,the following prevention and control measures are proposed:It is suggested to take engineering protection measures of sand barrier and diversion dike for pier No.2 to No.6,and engineering protection measures of diversion dike for pier No.l and No.7-9;It is suggested that tailings pond enterprises and downstream high-speed management units establish joint prevention and joint warning mechanism.