Research On Engineering Characteristics Of Fine-grained Tailings And Dam Stability

As one of the three basic facilities of mine production,the stability of tailings dam not only affects the normal production of mine,but also directly affects the safety of people's lives and property downstream.Therefore,it is particularly urgent and important to ensure the safety and stability of tailings dam body.At the same time,with the decline of mining grade of mineral resources and the continuous improvement of grinding technology in mining enterprises,the tailings particle size discharged into tailings reservoir gradually appears "refinement" phenomenon,which directly affects the safety and stability of tailings reservoir dam body.Therefore,based on the practical engineering background of an upstream tailings dam,the engineering characteristics of tailings materials and the influence of dam stability are studied by means of field experiments,laboratory experiments,theoretical analysis and numerical simulation.The grain deposition law of tailings dam body is analyzed,the engineering characteristics of different tailings particle sizes are explored,and the stability of tailings dam body is revealed by the change of particle size.Qualitative impact.The main research results are as follows:(1)The tailings deposition law of the accumulating dam body is analyzed by field and indoor experiments,and the tailings particle flow formula is established.The results show that the tailings of the tailings reservoir dam body have the macroscopical rules of "front coarsening and back fining","upper coarsening and lower fining",and can be generalized as the change process of "coarsening"-"slow thinning"-"thinning".The phenomenon of "particle size coarsening","interlayer","staggered layer" and "lens body" appears in the local position.At the same time,the formula of tailings particle flow shows that the starting and stopping of tailings particles on dry beach are mainly related to the "dragging force" of tailings slurry,and the deposition distance is related to the flow rate of slurry.(2)Tailings settlement experiments under different particle sizes were carried out,and the influence of particle size on tailings settlement characteristics was explored.The results show that with the increase of-0.074 mm tailings particle content in tailings,the earlier the "water-sand" interface of tailings slurry appears,the longer the settling time,the less obvious the stratification.At the same time,the settling mode will change from "independent settling" of single particle or floc to "whole settling" of flocculation net.After the tailings subsidence stopped,the depositional regularity of "thick bottom and fine upper bottom" appeared,and the phenomena of "interlayer","staggered layer" and "local coarsening" appeared in the bottom.(3)The micro-morphology of tailings particles is discussed.The results show that the surface of tailings particles is rough,multi-edged and angular,and the roundness is low.The shape of tailings particles is mostly irregular and granular.With the increase of tailings size,the roundness and axial coefficient of tailings decrease,and the roughness and edge angle increase.(4)Based on the fractal theory,the fractal dimension variation law of different tailings size was discussed,and the fractal dimension D was proposed as the index to characterize the tailings particle gradation.The results show that the fractal dimension of tailings increases and the pore fractal dimension decreases with the increase of-0.074 mm tailings particle content;the fractal dimension has a significant negative correlation with the tailings' coarse-fine ratio,that is,the larger the tailings' coarse-fine ratio,the more fractal dimension At the same time,when the fractal dimension D is in the range of 1.8863~2.631,the tailings particle size distribution is good.(5)The effect of particle size change on the compression consolidation and strength of tailings was studied.The results show that with the increase of-0.074 mm tailings particles,the compressibility of tailings increases,the compression coefficient and compression index increase,the stress-strain curve changes from strain hardening to strain softening,and the peak strength,shear strength and internal friction angle of tailings decrease,and cohesion occurs.Strength increases.With the increase of consolidation pressure,the peak strength of tailings increases,the void ratio and pore index decrease,and the secondary consolidation coefficient(Ca)increases.(6)The change of particle size will cause the change of slope of dry beach and permeability coefficient of tailings material,thus affecting the stability of tailings dambody.The influence of particle size on the stability of tailings dam is analyzed here.The analysis results show that the change of particle size of tailings entering reservoir will cause the change of slope of dry beach surface to have less influence on safety factor.With the increase of particle content of-0.074 mm,the safety factor of tailings dam body is smaller.The stability of tailings dam body will be reduced and the stability of tailings dam body will be increased by good sedimentary structure.