Study On Static And Dynamic Properties And Liquefaction Of Fine Tailings

Tailings are the deposits of a large number of ore crushed,selected and finely mined.China’s mineral deposits are abundant.After mining,sorting and extraction,the annual production of tailings is about 1.5 billion tons,while only 18.9%of the tailings are used for large-scale filling and recycling.Most of them are stored in tailings dam.In the era of sustainable economic development,the mining industry will continue to innovate in its research and technology,which will directly lead to the fine-grained development of mineral processing and mining.Fine-grain mineral processing and emissions are the general trend,and its hidden dangers will become more prominent.Therefore,in this paper,based on the characteristics of high stress and high pore water pressure of large high tailings dam,the static/dynamic mechanical behavior of tailings under high stress conditions is studied to establish a prediction model for the evolution and development of dynamic pore pressure of fine tailings materials.It provides theoretical support for the theoretical study of performance degradation of large high tailings dams.In this paper,a lot of researches are carried out on the effects of particle composition,dry density and consolidation ratio on the static/dynamic mechanical properties of tailings.The research methods,contents and results mainly include:(1)Taking the tailings material of Yinshan Lead-Zinc Mine located in Dexing City,Shangrao District,Jiangxi Province as the research object,basic physical test was carried out on its physical property index.The results show that the average moisture content of the sample taken is 9.3-18.6%,the average particle size of the whole tailings is 0.143mm,and the content of the larger group is greater than 0.075mm is 79.2%.The unevenness coefficient C_u of the tailings is 8.04,and the curvature coefficient C_c is 2.13.(2)In order to study the influence of fine particle content(clay granule and silt granule)on the shear strength parameters of tailings,the direct shear of different fine grain content,different axial loads and the conventional triaxial test under different confining pressures were carried out.Studies have shown that in the direct shear and triaxial tests,as the clay granule content increases,the cohesion force c of the test soil sample keeps increasing,while the internal friction angleφdecreases first and then increases;As the content of the silt granule increases,the cohesive force c of the test soil sample also keeps increasing,while the internal friction angleφincreases first and then decreases.In comparison,it was found that in the direct shear test,the critical fine grain content of the inner friction angle is changed,the clay granule particle is 10%,and the silt granule particle is 50%.In the triaxial test,the friction angle showed a turning fine grain content,and the clay granule particle is 15%,the silt granule is 40%.These critical fine particle contents are also verified in the p-q space.(3)In order to study the dynamic evolution of fine tailings under cyclic loading and the dynamics of dynamic pore water pressure during liquefaction,cyclic loading tests under different dry density,consolidation confining pressure and consolidation ratio were carried out.The research shows that under the same dry density and the same consolidation ratio,the consolidation confining pressure has little effect on the dynamic shear stress ratio;under the same confining pressure,the dynamic shear stress ratio has a certain increase with the increase of dry density.Under the same confining pressure,with the increase of relative compactness,the number of vibrations when the sample reaches liquefaction failure increases;when the relative compactness is consistent,the anti-liquefaction ability of the tailings has significant with the increase of confining pressure.When the consolidation stress ratio is K_c=1.0 or isostatic consolidation,the S type inverse sinusoidal trigonometric function model proposed by Seed can be used to predict the evolution process of dynamic pore water pressure,and for this test object and The similarity of similar soil sampleθis 1.4;when the consolidation stress ratio is K_c>1.0,that is,when the bias is consolidated,the Seed model is not suitable for the prediction of dynamic pore water pressure development.At this time,the exponential function model can be used to predict it.