Study On Stability And Dam Break Simulation Of Tailings Dam Under Rainfall And Water Level Change

Tailings pond is a structure for stacking tailings waste discharged from concentrator.The tailings stored in the pond contain a large number of pollutants.Once the tailings pond is unstable and breaks the dam,it will seriously endanger the safety of downstream residents,public facilities,and bring serious environmental pollution.Therefore,it is of great significance to study the safety and stability of tailings pond and dam break.Based on the research of domestic and foreign scholars,this paper takes Wanli tailings pond in Liaoyang County as an example.Firstly,the indoor rainfall model device of tailings soil slope is established,the shallow stability test of slope under rainfall conditions is carried out,and the volumetric moisture content,pore water pressure and slope failure mode of slope are monitored.Secondly,FLAC3 D is used to simulate and calculate the seepage stability of tailings dam under the change of water level in the reservoir caused by rainfall,analyze its landslide mechanism and monitor the displacement and deformation of tailings dam.Then Rhino is used to establish a fine topographic map of the tailings pond and the downstream area.Taking the FLAC3 D analysis results as the prerequisite for dam break simulation calculation,the evolution of dam break debris flow in the downstream of the tailings pond is simulated in Fluent,its inundation range and flow speed are analyzed.Finally,the analytic hierarchy process is used to evaluate the safety risk of the whole tailings pond area,sort out each index and establish a hierarchical model,determine the weight of each index,analyze its safety state in combination with the actual situation of Wanli tailings pond.The main conclusions are as follows:（1）The results of shallow stability of tailings pond under rainfall conditions show that the infiltration velocity of slope is slope top > slope toe > slope middle.With the increase of slope ratio,the infiltration rate at the slope toe is faster.The increase of pore water pressure is after the water content is saturated.The volume water content threshold is very important to determine the failure of slope.The depth of wetting peak decreases gradually with the increase of slope ratio,and the resulting surface runoff scours the slope surface to form a shallow layer.The larger the damage range is,the more sediment loss is.（2）The buried depth of phreatic line of tailings dam decreases with the rise of reservoir water level.When overtopping water level,the phreatic line of dam crest moves downward along the slope,making the dam crest partially saturated.From the normal water level to the flood level,the shear zone continuously extends to the interior of the dam body in the longitudinal direction.When the flood overtopping,the phreatic line moves downward along the slope,which makes the dam crest partially saturated and preferentially damaged,and the shear zone shortens sharply.（3）The potential sliding surface in case of instability is calculated by FLAC3 D stability analysis software,which is used as the breach.Rhino is used to establish the fine terrain downstream of the tailings pond.The stability analysis results are used as the initial conditions for dam break simulation in fluent and calculated,and the flow state of mud and sand is obtained: under the narrow terrain of the valley,the mud and sand have the collection flow with fast flow velocity,large mud and sand flow and small inundation range;In flat areas such as farmland,silt has divergent flow with slow flow velocity,small silt flow and wide inundation range.By setting the surface roughness,the deviation between the simulation results and the actual situation can be effectively reduced.（4）The safety risk assessment of tailings pond includes five criteria layers: safety management,natural conditions,tailings dam,flood drainage system and tailings transmission and return water system.The hierarchical model of safety risk assessment of tailings pond is established.The judgment matrix is established,and the weight value of each index in the reservoir area hierarchical model is calculated by AHP（analytic hierarchy process）.Taking Liaoyang Wanli tailings pond as an example,the safety risk assessment of Liaoyang Wanli tailings pond is carried out to determine its safety level.Through calculation,it can be seen that the tailings pond is in a safe state.