Study On Humidification Deformation Characteristics Of Unsaturated Copper Tailings

Copper mine tailings,also known as copper tailings sand,are composed of fine grains of sand left after ore crushing and selecting.The grinding roundness of copper tailings is relatively high.Particles with particle size less than 0.075 mm account for the majority,and the plastic index ranges from 10 to 17.Combined with particle size analysis and liquid-plastic limit test,it can be concluded that the copper tailings sand belongs to silty clay.According to the properties of clay and permeability coefficient of geological report survey,tailings sand has good water holding capacity and is not easy to filter water.Because of its special physical and chemical properties,the content of heavy metals in tailings is very high.Copper tailings reservoir is the accumulation body of copper tailings,with large volume and high accumulation.It is the by-product of the ore production process.The safety and stability of the tailings reservoir is not only closely related to the safety production of mining enterprises,but also has a significant impact on the lives and property of the surrounding residents and the local ecological environment.The strength of tailings is one of the main factors affecting the stability of tailings reservoir.In order to study the deformation characteristics and mechanism of unsaturated tailings with different moisture content,two test methods of increasing moisture content by grading and continuous humidification are proposed in this paper.The problem of humidification of unsaturated tailings is solved and the continuous humidification of samples is preliminarily realized.Combining with the properties of tailings sand,it is applied to the dam,and the numerical simulation of tailings dam is carried out.The details are as follows:1)Designing the experimental scheme,carrying on the basic experimental research,judging the basic properties of copper tailings sand,and investigating the local climate conditions,providing the basis for the humidification scheme of copper tailings sand.2)Triaxial tests of unsaturated soils were carried out.Two different humidification schemes were designed to study the shear strength characteristics of unsaturated copper tailings.It is concluded that:(1)the unsaturated tailings sand specimens show plastic failure,the failure strength increases with confining pressure,the stress-strain characteristics show shear hardening,and the degree of hardening increases with confining pressure;(2)the volume-strain relationship of unsaturated copper tailings during shear process increases with confining pressure,and the volume-strain also increases gradually,when the strain and volume-change are small.At present,the confining pressure has little effect on the stress-volume change relationship of soils;(3)through the analysis of the time effect of wetting deformation,it can be concluded that in the first stage of the wetting process,the matrix suction is from 80 k Pa to 50 k Pa,and the amount of wetting deformation is the most obvious,accounting for about 80% of the total wetting deformation;(4)through the analysis of the time effect of saturation,it can be seen that the saturation of soils increases with the matrix.The suction decreases and increases gradually.The first stage is the fastest growth of saturation,and the subsequent stage is gradually stable to reach saturation.3)On the basis of the existing non-linear constitutive relationship of unsaturated soils,a non-linear constitutive model of unsaturated tailings sand is established according to the data in relevant literatures and some experimental data of wetting deformation.Three relationships related to matric suction are obtained by fitting,including the relationship between water content and matric suction,the relationship between soil tangent volume model and matric suction,and the relationship between water tangent bulk modulus and matric suction.The tangential bulk modulus of soil and water are introduced into the software by using this formula.The conclusion can be drawn as follows:(1)From the settlement diagram of the dam body,it can be seen that the maximum settlement is between h/3-h/2,and the maximum stress of the dam body is at the central position.(2)The settlement deformation of tailings dam body is larger than that of its horizontal displacement,and the settlement deformation is approximately two times of that of the horizontal displacement.