冻融循环作用下尾矿砂抗剪强度和变形特性研究

为探究冻融循环后尾矿物理力学特性的变化特征,使用高低温试验箱和应变控制式三轴剪力仪对处于不同初始条件下的尾矿砂进行不排水不固结试验,揭示了尾矿砂的抗剪强度参数、不同围压条件下的变形模量与冻融循环次数、含水率之间的关系。结果表明:相同含水率条件下,随冻融循环次数增加,尾矿砂黏聚力先减小后趋于稳定,内摩擦角先增大后减小,围压100 k Pa和200 k Pa时变形模量逐渐减小,围压300 k Pa时变形模量呈现先减小后缓慢增大的趋势;相同冻融循环次数条件下,随尾矿砂含水率增加,其黏聚力先增加后减小、内摩擦角不断减小;不同围压条件下变形模量在总体上均呈现出不断减小的变化趋势,围压200 k Pa时变形模量总的衰减量最大,100k Pa次之,300 k Pa最小。

Deformation behaviors of the tailing sands under the shear strength and freezing-thawing recycling impact

The given paper is aimed at a simulated investigation and exploration of the changing features of the physical and mechanical properties of tailing mines under the impact of the freezing and thawing alternative cycles.For the said purpose,we would like to conduct a dissolidation undrained test with the mining tailings under the recycling conditions of different freeze-thaw and moisture content in a high-low temperature alternatively changing testing-box and the strain controlled tri-axial apparatus,so as to gain the shear strength parameters (the cohesion and internal friction angle) based on the Mohr-Coulomb strength theory,for the above tests can help us to work out the relation between the shear strength parameters and the recycling time of the freezethaw,the moisture content and the variation of the deformation modulus in the freezing-thawing cycles,in addition to the different confining pressures.The testing results show that,on the condition at the same amount of moisture content,the cohesion of the tailings tends to decrease first and then gets to be stable with the increase of the freeze-thaw cycle.In the early stage of the said cycle,the attenuation tends to be more obvious but gets decreased slowly later.And,in comparison,the internal friction angle also tends to increase first and then decrease while the variation quantity decreases with the increase of the cycle going-on.However,when the confining pressure is getting to the range between 100 kPa to 200 kPa,the attenuation tendency of the deformation modulus would become smaller at the early stage,but then tends to increase in the middle and then tends to stay at a certain range later.But,when the confining pressure increased to 300 kPa,the deformation modulus would reach its utmost at first and then continue to increase slowly at the middle stage till the last stage.What is more,under the condition of the same freeze-thaw cycles,the cohesion also tends to increase first and then decrease with the increase of the moisture content of the tailings till reaches the maximum value of 23.17 kPa at the moisture content of 8％.Thus,there prove to be existing a regular gradual declining tendency with the increase of the moisture content for the three stages of the internal friction angle.To be more accurate,the deformation modulus of the freeze-thaw cycles under different confining pressures indicate a decreasing tendency on the whole when the total attenuation of the deformation modulus turns to be the most obvious at the confining pressure of 200 kPa,whereas the minimum attenuation takes place at the pressure of 300 kPa,with the middle attenuation point taking place at that of 100 kPa.Thus,the research results can be expected to enrich the strength theory of tailing sand in a permafrost region and provide some valuable reference for the safe development of the permanent frost regions and the related projects of tailings.