Study On The Particle Distribution Law And Direct Shear Mechanical Properties Of Tailings Stacking Process

Tailings is the main deposit of tailings pond.The stability of tailings is one of the important factors affecting the stability of the dam.A large number of literatures have studied the influencing factors of the shear strength of tailings,There are few studies on the influence of particle size distribution on shear strength during tailings stacking.In this paper,we intend to carry out tailings test,stacking test,seepage test and shear strength test to obtain the particle size distribution law of a fixed horizontal tailings under overburden pressure and seepage during the stacking process,and to explain the internal mechanism of the relationship between different stack heights and shear strength indicators,providing experimental basis for studying the relationship between tailings stability and stacking height.The main findings and conclusions are as follows:(1)Compared with the sieving method and the laser particle size method,the results of gradation measurement of tailings particles are obtained.When the particle size is less than 37?m,the error of the screening method is larger,and the laser particle size test results are closer to the actual situation.The unevenness coefficient and curvature coefficient of the test tailings were 19.75 and 1.14,respectively,and the particle gradation was good.(2)Study on the particle size distribution of tailings stacking process through stacking test.In the tailings stacking process,the stacking height has a power function relationship with its overlying pressure.The content of tailings particles larger than 37?m decreases with the increase of stress.The content of tailings particles with 10~37?m increases first and then decreases with the increase of stress.The particle content of 1~10?m particles increases with the increase of stress,0.1 The particle content of the ~1?m particle group did not change significantly with the increase of stress,and the relationship between the particle content and stress of different particle groups was obtained.(3)In order to study the particle size distribution law of tailings affected by seepage flow under different stacking heights,the tailings seepage test is carried out.The influence of seepage on the particle size distribution of the test tail has a critical height of 156.88 m,when the height is less than 156.88.When m is used,the loss of fine particles is the main reason for the change of particle size of tailings.The lost fine particles are mainly 1~10?m particles,followed by 0.1~1?m particles;the stacking height is more than 156.88 m,and the seepage is fixed.The effect of horizontal tailings particle size is not significant.(4)Through direct shear test,the influence law of stacking height on the direct shear mechanical properties of tailings is studied,and the main factors affecting the shear strength characteristics are the change of water content,dry density and particle size with stacking height.The cohesive strength of the shear strength index increases first and then decreases with the increase of the stacking height,and then increases slightly.The internal friction angle decreases first and then increases with the height of the stacking height,and then changes.Trend;and when the stack height is 156.88 m,the cohesion is the largest and the internal friction angle is the smallest.Based on the particle swarm optimization algorithm,the relational model of the strength index of tailings is obtained by multi-factors.