Study On The Seepage Failure Mechanism Of Graphite Tailings Dam

Mineral resources are rich in China.However,due to the low grade of most mineral resources,a large amount of tailings will be produced during hydraulic step-by-step separation.The sorted tailings are discharged as mortar,and the tailings pond is built to solve the problem of tailings accumulation.As the main structure of the tailings pond,the tailings dam has frequent accidents in recent years.According to statistics,more than half of the accidents are seepage damage.Among them,continuous rainfall,hydraulic separation and other surface runoff are the factors that induce the destruction of tailings seepage.The Yunshan Graphite Mine in Luobei County,Hegang City,Heilongjiang Province has the largest reserves in Asia.It produces a huge amount of tailings.If the seepage damage occurs,a large amount of accumulated tailings will flow downstream and cause huge economic losses.Therefore,it is of great significance to study the seepage failure mechanism of the graphite tailings dam.This thesis focus on the seepage failure mechanism of tailings dams under the action of rainfall and other surface runoffs,and analyzes the physical and mechanical properties of the graphite tailings sand.Based on the principle that the soil-water characteristic curve is similar to the particle analysis curve,the relationship between the matric suction and moisture content was established to explore the laws of tailings dam destruction By using the percolation model of different tailings dam,the seepage damage mechanism of tailings dam was revealed.The main research work is as follows:(1)The physical,chemical and mechanical properties of the graphite tailings sand were analyzed.Based on the experimental analysis of the chemical composition,particle size gradation,relative density,permeability and strength characteristics of graphite tailings sand,the graphite tailings sand in Hegangis is classified as chemically unstable and poorly graded silt sand with low shear strength.(2)The soil-water characteristic curve(swcc)and permeability function were given.Based on the principle that the particle analysis curve is similar to the soil-water characteristic curve,the correction coefficient α was obtained considering the shape of the tailings sand and the model safety,and the swcc curve was fitted and corrected by the Van Genuchten model.The soil-water characteristic curve of graphite tailings sand was given,and the permeability function was established based on the swcc and saturated permeability coefficient.(3)A seepage analysis model for tailings dam was established.The graphite tailings dam seepage analysis model was established through material selection,boundary conditions,initial conditions,and the introduction of permeability functions.The displacement change rule under the ground stress balance was given by analyzing the balance of ground stress.The operation of the seepage module of the tailings dam was stimulated via setting of the rainfall intensity.(4)The seepage failure mechanism of Luobei tailings dam was proposed.Through the analysis of the stability of the tailings dam under different dam heights and rainfall intensities,the seepage failure of the tailings dam includes four stages:shallow sliding stage,deep sliding stage,penetrating surface stage and piping stage.Recommendations for tailings pond management were given through the destruction mechanism of tailings dams.