| Tailings dams are a major source of danger in mines.Once a dam breaks,it will cause huge loss of life and property and environmental pollution.China is a major mining country with frequent earthquakes and high seismic intensity.Some provinces have more tailings ponds and are located in areas with high seismic intensity,which increases the risk of dam failure caused by earthquakes.Due to advances in beneficiation technology,the tailings have become finer and finer.In addition,many mines use coarse-grained tailings for underground filling,and the fines content of the tailings in the reservoir is increasing,resulting in a weakening of the tailings dam’s seismic resistance.Therefore,this paper takes a tailings pond in Sichuan as the engineering background,and uses theoretical analysis,laboratory tests,model tests,and numerical simulations to analyze the effects of fine particle content on the macro and meso nature of the tailings and the tailings pond.The microscopic mechanism of the change of tailings dynamic characteristics caused by the change of fines content is studied.The influence of fines content on the dynamics of tailings materials is studied.The dynamic response characteristics of dams under different fines content tailings are discussed.The main research results are as follows:(1)The effects of fine particle content on the macro and meso nature of tailings and tailings ponds were analyzed through laboratory tests,model tests and numerical simulations.The results show that with the increase of fine particle content,the plasticity index generally shows a gradual increase trend;the permeability coefficient of tailings gradually decreases and the rate of decrease increases,when the fine particle content reaches 80%,100%,the tailings infiltration The coefficient decreases by an order of magnitude;the general trend of the tailings grading situation is: from general to good to average;the maximum pore ratio and the minimum pore ratio decrease first and then increase;the strong chain gradually decreases,the weak chain gradually increases,the total force As the number of chains continues to increase,the fine-grained tailings are subjected to greater and greater forces,and the loadtransmitted by the coarse-grained particles is gradually carried by the fine-grained particles.(2)The microscopic mechanism of the influence of fine particle content on the dynamic characteristics of tailings was explored using electron microscope scanning test,image processing technology and XRD test.The results show that the sandy tailings consist of granular particles,the powdery tailings contain some plate-like particles,and the viscous tailings consist of flaky and detrital particles.This flaky structure makes it easier to crush and is not conducive to crushing The increase of dynamic strength;the viscous tailings particles have an electric double layer structure,which shows a microscopic adsorption phenomenon,which is conducive to the improvement of dynamic cohesion;as the content of fine particles decreases,the content of primary minerals with higher hardness increases and the hardness is lower The low content of secondary minerals reduces the tailings’ dynamic strength.(3)Calculating and analyzing the shape parameters of tailings particles found that with the increase of particle size,the roundness and flatness generally showed a decreasing trend,and the convexity,angular parameters,roughness and fractal dimension generally showed an increasing trend;With the increase of particle flatness and angular parameters,the dynamic internal friction angle gradually increases and the growth is slower and slower.(4)The fractal dimension of tailings was calculated and analyzed using fractal theory.The results show that with the increase of fine particle content,the overall situation of tailings grading is: from general to good to general,the judgment result of fractal dimension is basically consistent with the discrimination result of curvature coefficient and unevenness coefficient;Increasing particle size fractal dimension and surface fractal dimension are gradually increasing,pore fractal dimension is gradually decreasing,the correlation degree of particle size fractal dimension increases first and then decreases,when the fine particle content is 30%,the correlation degree is the highest,gradation Preferably,the skeleton is more stable.(5)Through the dynamic triaxial test,it was found that with the increase of fines content,the dynamic compression elastic modulus,initial dynamic shear elasticmodulus and maximum dynamic shear stress of the tailings generally showed a decreasing trend;the tailings resisted liquefaction The strength increases first and then weakens,and decreases to a very small amount.When the fine particle content is about 34%,the anti-liquefaction strength is the highest.The tailings skeleton is relatively stable.(6)The numerical simulation results show that as the fine particle content of the dam tailings increases,the burial depth of the infiltration line gradually becomes shallower.When the fine particle content exceeds 60%,the burial depth changes rapidly;the maximum horizontal displacement value is almost unchanged,and the maximum displacement occurs The area is expanding;the liquefaction area is continuously expanding towards the dam slope,the area of the liquefaction area is increasing,and the area percentage of the liquefaction area increases linearly;the minimum safety factor of the dam body gradually decreases,and the dynamic seismic resistance of the dam body gradually decreases,and the fine particle content exceeds60 %,The safety factor decreases rapidly.. |
