| Tailings reservoir refers to the place where tailings or other industrial waste are discharged after ore separation in metal or non-metal mines,which is composed of dam mouth or enclosure.It is also an essential facility for the operation and production of mining enterprises.As a large mining country,there are more than six thousand tailings reservoirs in China,and a large number of tailings reservoirs are distributed in areas where earthquakes are more active.According to statistics,earthquakes have become the second largest natural factor leading to the failure of tailings dams.In order to enhance the disaster prediction and prevention and control ability of tailings dams under earthquakes and improve the understanding of the dynamic response characteristics of tailings dams,this paper takes a tailings reservoir in Sichuan as the engineering background,and studies the dynamic characteristics of tailings materials under different conditions through field investigation,theoretical analysis,laboratory test and numerical simulation.The main research results are as follows :(1)Through the field investigation of the tailings pond,the surface tailings of the dry beach surface with different lengths from the sub-dam were sampled,and the particle size and deposition law of the samples were analyzed.It was found that the particle size gradually became finer from the sub-dam to the tail of the tailings pond,and the particle size of the tailings changed at a distance of 10 m ～ 15 m from the sub-dam,and the water content,density,particle size and permeability coefficient of each tailings sample were further summarized.(2)The dynamic strength,dynamic pore water pressure,dynamic stress-strain curve,dynamic modulus and damping ratio of different tailings samples were studied by theoretical analysis and indoor dynamic triaxial test.The test results show that the dynamic strength increases with the increase of confining pressure and tailings particle size,and there is a power function relationship between the dynamic stress and the vibration times required for the failure of tailings samples.The liquefaction mechanism and influencing factors of tailings are expounded by using the principle of limit equilibrium.It is found that the development and growth of pore pressure of tailings samples under cyclic loading has obvious stages,and the growth trend of dynamic pore pressure of tailings under different conditions is fitted by Bi Dose Resp function,and the fitting effect is good.The stress-strain curve of tailings sample under dynamic load is analyzed.According to the stress state of the sample,the hysteresis curve is divided into three stages : elastic strain,plastic failure and softening deformation.A calculation method for estimating the hysteresis area of stress-strain curve is proposed.This method can be applied to calculate the damping ratio and dissipated energy of tailings sample.It is found that the dissipated energy of tailings has a clear correspondence with the increase of pore pressure.(3)Taking a tailings reservoir in Sichuan as the engineering background,the liquefaction mechanism of the dam body is analyzed by the shear stress comparison method,and the anti-liquefaction shear stress ratio curve and dynamic parameters of each tailings material are obtained by indoor dynamic test.The liquefaction area of the tailings dam is determined,the development law of the liquefaction of the dam body during the continuous process of seismic waves is analyzed,and the liquefaction area of the dam body is analyzed and verified.(4)The dynamic stability of the dam is analyzed by time history analysis method,and it is found that the propagation of seismic wave in tailings dam has obvious whiplash effect.By analyzing the initial seepage field and stress field of the tailings dam,it is found that the effective stress,pore pressure and saturation line of the dam are increased under the action of earthquake.By analyzing the vector deformation of the dam body,it is found that the deformation of the tailings dam under the action of the earthquake is in the form of the upper part of the accumulation dam sinking downward and the lower part of the accumulation dam squeezing out to the free surface.The time history development laws of instantaneous safety factor,minimum average safety factor and average small safety factor of dam body are further analyzed,and the principles,advantages and disadvantages of various calculation methods are expounded.(5)The influence of common factors of tailings reservoir on the minimum safety factor,liquefaction range and displacement of dam body is discussed,and the sensitivity of each factor to the dynamic stability of dam body is analyzed.The results show that the minimum safety factor and liquefaction range of dam body are mostly in good linear relationship under the change of the above factors.This conclusion can provide a good prediction for the dynamic stability of tailings dam under different conditions. |
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