Meso And Macroscopic Mechanical Properties Of Tailings During Drying-wetting Cycles

Because of the tailings dam is usually constructed by using natural landform of undulation,affected by natural climate and ore-mining process.The tailings sand is in the state of cyclic that moisture absorption and dehumidification which will inevitably lead to changes in the mechanical behaviors of the tailings in the dam,and have an impact on the stability of the tailings dam.Therefore,it is of great theoretical and practical significance to study the changes of mechanical behaviors of tailings under repeated drying and wetting cycles.In this paper,a self-designed device is used to study the mechanical behaviors of tailings in drying-wetting cycles.A tailings dam in Hunan province is taken as the research object.The mechanical behaviors and mesoscopic fabrics of tailings are measured by using triaxial apparatus and stereoscopic microscope after the 0 to 6 drying-wetting cycles.The main research results are as follows:(1)There are regular certain changes in stress-strain curves,pore water pressure,static strength and shear strength index of tailings during the reduplicative drying-wetting cycles,and it caused very significant impacts on the linear and nonlinear deformation characteristics of tailings during triaxial tests.(2)The static strength of the tailing samples have slowly andgradually decline in the whole course of 0 to 6 drying-wetting cycles,and reached the lowest value after sixth cycle.But there are different degrees of decline in diverse cycle stages.The decrease is the largest in the medium-term experience of 2 to 3 cycles,and the static strength of the samples does not decrease continuously but has a slight increase in the period of fourth cycle.(3)At the mesoscopic level,there are different degrees of changes in size distribution characteristics of particle,the change of poriness,the distribution characteristics of pore size and the fractal dimensions of aperture in the drying-wetting cycles.It indicates that the changes in mechanical behavior of tailings is mainly due to changes in its meso-structural structure.(4)The static strength have slowly and gradually decline of tailing samples with different initial dry density during the reduplicative drying-wetting cycles.In the cycles of 0 to 3,the intensity of the decline is less than that of the latter in the periods of 3 to 6 cycles to tailings with lower initial dry density,while the tailings of high density have antipodal results.