Numerical Simulation Study On The Stability Of A Tailing Dam By Particle Flow Code

The safety of tailings dam is directly related to the safety of people's life and property,the natural environment and the interests of mining enterprises.In order to study the macro-meso failure mechanism of tailings dam,this paper combined with the National Key Research and Development plan project"Key Technology Research and Application Demonstration of Large and High Tailing Dam Disasters Prevention and Control?2017YFC0804601?",a tailings dam project in Jiangxi Province as the example,using the laboratory experiment and numerical simulation methods,there is a study on the particle flow simulation of the tailings dam from the macro and micro level.This method makes up for the shortcoming that the limit equilibrium method must assume the slip surface and cannot analyze the failure process.The main contents and results of the study are as follows:?1?Through the particle size analysis,the tailings layer is divided into four layers:the tail silt,the tailings,the tail clay and the tailings mud,And the direct shear test was carried out respectively to obtain the parameters of shear strength and water content etc.?2?Using particle flow software PFC^2D biaxial more than 300 groups of different parameters test,Results show that:there are mesoscopic parameters with strong cohesiveness sensitivity.They are the normal contact stiffness and tangential stiffness ratio,the normal bond strength and the tangential bonding strength ratio,and the negligible sensitivity weak mesoscopic parameter is the friction coefficient.The mesoscopic parameters with strong internal friction angle sensitivity are normal bonding strength and tangential bonding strength ratio,particle bonding strength.On this basis,The biaxial compression test of tailings layer and bedrock sample was carried out by disk particle?ball?model respectively;At the same time,The biaxial compression test of the initial dam sample was carried out by particle clusters?clump?model respectively,the meso-parameter calibration of tailings dam is completed.?3?Based on the theory of strength reduction,the tangential bond strength and friction coefficient of particles are reduced.It counted that the safety coefficients of normal water level and the flood level are 2.67 and 1.83 respectively by PFC.The safety coefficient of the normal water level calculated by Bishop,Janbu and Morgenstern-price is 2.126,2.079 and 2.128respectively,and the safety coefficient of the flood level 1.624,1.550 and 1.563 respectively.The calculation result of PFC is too large,because there is no systematic theory matching between macro meso parameters.The mechanical properties of granular aggregate are different from that of actual materials,and particle size effect will improve dam safety factor.?4?The damage of the initial dam is more obvious than that of the stacking dam.At the normal water level,the initial dam is a local sliding failure,which shows that the soil in the dam foot is sliding forward,the dam is blown up to the foot of the dam;and the lower part of the stacking dam is earlier and more obvious than the upper slide.At the flood level,the initial dam is the whole sliding failure,and the stacking dam is the lower part of the first big slide,and the upper slide is aggravated.?5?Under different rainfall conditions,with the increase of the early strength of initial dam,the safety coefficient of tailings dam is improved,and the displacement of each monitoring point decreases;With the early strength of initial dam unchanged,flood water level displacement of each monitoring point is large than the normal level.At the same time,the displacement of the dam top,dam and dam foot decreases in order.The strength of the initial dam composed of viscous material?masonry dam?is higher than that of unbonded material?rockfill dam?,and the safety factor of tailings dam is higher.