Research On Seepage And Shear Strength Characteristics Of Saturated-Unsaturated Mine Tailings

The tailings dam is recognized as dangerous source of mud-sand flow with high potential.In recent years,with rapid development of industrial,failure of tailings dam is experiencing a rise trend.The distribution of water inside dam is an important factor of dam safety.In order to make clear of distribution state of water inside dam after seepage and it's way of affecting dam safety,this paper mainly deal with the following researching and discussion.(1)Use analytic method to solve saturated and unsaturated seepage equation,the solution is in the form of infinite series,because of good convergence of solution,only a few items is enough while the solution is used.It can be concluded that complex problem like tailings dam can be solved analytically,but it needs some simplification and assumption.(2)By the usage of self-designed instrument,experiments of unsaturated tailing sand are committed,and datum of water spatial distribution inside the dam is gained.By the field experiments of tailings dam,datum of seepage line is gained.The correctness and practical application value of analytical solution is verified by sythesis of experiment datum and analytical solution.The results show that theoretical calculation results and the experimental datum is match to each other regardless of saturated or unsaturated seepage problem.These unknown parameters of analytical solution can be calculated by chaotic particle swarm optimization(CPSO)on basis of combination of experiment datum.(3)Through conventional direct shear tests,relation between water content and shear strength,between velocity and shear strength are gained.The test object include coarse and thin tailing sand.The results show that cohesion will increase first and then decrease while water content is increase,internal friction angle will decrease while water content increase,for coarse tailing sand,cohesion has nothing to do with shear velocity under most water content,internal friction angle has nothing to do with shear velocity.For thin tailing sand,cohesion is going to increase while shear velocity increase,internal friction angle will decrease while shear velocity increase.(4)Strength characteristics of saturated tailing sand in principal stress space is obtained by using of hollow cylinder apparatus.Results show that in meridional plane,characteristics of failure curves is that change rate is going to smaller and smaller.In p plane,while hydrostatic pressure is small,failure curve is close to Mohr-Coulomb criterion,while hydrostatic pressure is big,the failure curve is close to Drucker-Prager criterion.(5)By using of synthesis method,space distribution characteristics of water content and relation between water content and shear strength can be merged togetherly,then space distribution characteristics of shear strength is come up,if put space distribution characteristics of shear strength into calculation model it's influence to tailings dam safety can be obtained.The results show that the safety of the dam is reduced on the basis of the original foundation as soon as unsaturated part of dam is considered.