Experimental Study On The Blocking Mechanism Of The Tailings Dam And The Evolution Law Of Seepage Performance

The tailings pond is one of the main engineering facilities for metal or non-metallic mines to store tailings in the production process,but it is also a potential source of danger for the mine.As one of the tailings dam engineering systems,the drainage system is responsible for maintaining the tailings important responsibility for seepage stability of the dam.However,due to the physical properties of the tailings itself,and the influence of factors such as microorganisms and metal ions in the leachate,the dam body and seepage of the tailings dam will be caused as the seepage time passes.Fouling of the facility,which in turn leads to a decrease in the permeability of the tailings dam,an increase in the infiltration line,and even the danger of dam failure.In order to analyze the causes of the blocking of the tailings dam and master its blocking rules,the blocking phenomenon has been experimentally studied in this paper.The main research contents and conclusions are as follows:1.Taking the silting phenomenon of the Yinshan tailings dam as the engineering background,through field survey and sampling analysis,it can be seen that the drainage performance of the tailings dam drainage system has greatly decreased,and the geotextile clogging of the reverse filter layer is serious;The main metal ion isCa²⁺with Fe²⁺,The main types of anions areSO₄^2-、Cl^-with F^-;The microorganisms in the seepage environment of the tailings dam come from the bacterial world.（proteobacteria）Dominate.2.Analysis of the clogging causes of geotextile clogging from physical,chemical,and external factors.The analysis results show that tailings intrusion,tailings water immersion,and vertical load cause the geotextile’s reverse filtration performance to decrease.Based on this,a chemical solution soaking test of similar composition was carried out to verify that metal ions have a significant chemical blocking effect on tailings and geotextiles.A high-stress seepage test was also carried out,and the test results show that under high vertical stress conditions As a result,the permeability of tailings and geotextiles will decrease significantly.3.Independently developed a new simulation test device for blockage,carried out a blockage simulation test,and analyzed the blockage laws of geotextiles with the help of a micro-CT scanner and avizo software.The test results show that:（1）in the initial stage of seepage,The clogging of the geotextile and tailings particle skeleton outside the drainage pipe is the main reason for the decrease in the seepage rate of the drainage pipe;（2）Chemical blocking mainly occurs in the unsaturated seepage area,which can explain that oxygen is a necessary condition for chemical blocking.（3）The clogging of the geotextile is mainly carried out in the thickness direction.From the upper surface to the lower surface of the geotextile,the degree of the clogging shows a change law that first increases and then decreases.About 0.3mm below the upper surface.4.According to the actual spatial positional relationship of drainage pipe,geotextile and tailings,a"soil-cloth combination"sample was designed,a chemical solution seepage test with similar composition was carried out,and the seepage under different seepage conditions was fitted.The mathematical expression of the coefficient over time.The test results show that the chemical blocking effect of metal ions on the soil-cloth combination sample is obvious.Under the condition of seepage flow of the chemical solution containing iron ions,the seepage curve shows a concave shape.In the case of calcium ion under the seepage condition of the solution,the seepage curve showed three stages and the unevenness was obvious,that is:the initial stage,the permeability coefficient decreased in a concave shape,and the decline rate gradually decreased;in the middle stage,the slope of the seepage curve approaches zero,and the permeability coefficient tends to stable;in the later stage,the permeability coefficient declines convexly,and the rate of decline gradually increases.In addition,the greater the concentration of metal ions in the percolation solution,the greater the decline in the permeability coefficient of the sample and the more severe the blockage.5.The scanning electron microscope was used to obtain the microstructure of the geotextile after seepage of the chemical solution,and the cause of its clogging was analyzed.The analysis shows that the clogging material generated by the hydrolysis reaction of metal cations gradually adheres and consolidates in the geotextile fibers In the above,the reduction of the fiber pore diameter of the geotextile is the direct cause of the chemical blockage of the geotextile.Based on this analysis,the calculation formula of the reverse pore diameter of the geotextile after filtration is derived.6.Based on the results of the high-stress seepage test,the simulation results of the fouling test,and the seepage test results of similar solutions of chemical solutions,the parameters that are easily available in the laboratory were selected from the physical,chemical,biological,and external environmental factors.Tailing dam silting risk coefficient and silting risk evaluation standard.