Experimental Study On Properties And Steady State Of Saturated Tungsten-molybdenum Tailings

An upstream tailings dam in southern Jiangxi Province is formed by the accumulation of tungsten-molybdenum tailings on site.The permeability of such dams is poor with high saturation line.The dam body is not dense and its mechanical properties are relatively poor.Therefore,the seismic liquefaction usually occurs under the action of earthquake load,and whether liquefaction will further cause the flow-slip damage is controlled by the steady-state strength of the saturated tungsten-molybdenum tailings.Based on the steady-state theory,a series of experiments on the basic physical and mechanical properties and the steady state of tungsten-molybdenum tailings in a tailings dam in southern Jiangxi Province are carried out.The main conclusions are as follows:(1)The parameters of basic physical and mechanical properties of tungsten-molybdenum tailings were obtained by routine geotechnical tests,and the parameters of Duncan-Chang E-μ model under drainage conditions were obtained to make up for the blank parameters of DuncanChang model for tungsten-molybdenum tailings in southern Jiangxi Province.(2)Saturated tungsten-molybdenum tailings have two kinds of drainage shear characteristics: shear contraction,the first shear contraction after dilation.Under low confining pressure,the stress-strain curve of loose tailings is strain-hardening type,which shows the shrinkage characteristics.The stress-strain curve of dense tailings is strain softening type.At high confining pressure,the dense tailings dilatancy completely disappeared,which exhibited the same shrinkage characteristics as the loose and medium-density tailings.(3)The shear deformation characteristics of saturated tungsten-molybdenum tailings are significantly affected by the content of fine particles.Under the same effective consolidation confining pressure,there are three stress-strain curves of saturated tungsten-molybdenum tailings: strain-hardening type,strain-stabilized type and strain softening type.In the process of increasing the content of fine particles from 15 % to 22 %,the stress-strain curve of tungstenmolybdenum tailings transition from strain hardening to strain stability.When the content of fine particles is higher than 30 %,the stress-strain curves under different confining pressures all become strain softening.(4)The steady-state selection criteria of CD and CU test are different.When the axial strain of the specimen reaches about 35 % during the CD test,the specimen reaches the steady state.When the axial strain of the specimen reaches 20 % during the CU test,the specimen reaches a steady state.(5)Drained triaxial tests showed that steady state is the intrinsic property of saturated tungsten-molybdenum tailings,which is not affected by the external conditions such as relative density and confining pressure,and the steady-state line is unique.The change of fine-grained content has a significant influence on the steady-state line of saturated tungsten-molybdenum tailings.With the increase of fine-grained content,the steady-state internal friction angle of saturated tungsten-molybdenum-molybdenum tailings gradually decreases,and the steadyFlow area continues to decrease,that is subject to the same load,the more prone to liquefied flow slip damage.Therefore,it is suggested that enterprises should strictly control the content of fine particles in the process of tailings damming,and do a good job of dam safety monitoring and assessment of liquefaction potential.