Experimental Study On Physical And Mechanical Properties And Microstructure Of Iron Ore Tailings

With the progress of national science and technology and the update of mineral processing technology,a large amount of industrial fine powdery tailing sludge wastewater will be produced in the mining process,which is directly discharged into the tailings reservoir.The reservoir surface is always in a fluid-plastic state,and its hidden danger is great.Once the dam breaks,it will cause huge disasters and losses.Due to the fine particle size and high water content of the tailing mud,it is difficult to consolidate and accumulate.Therefore,the state requires that the industrial tailing mud produced by mining enterprises must be treated by pressure filtration and dehydration before being discharged into the tailing pond.Therefore,it is necessary to carry out relevant research on the tailing mud.In this paper,the tailing mud of an iron mine in Zhashui area,Shaanxi province is taken as the research object.Basic indoor geotechnical test,static and dynamic triaxial test and microscopic test are carried out on the tailing mud.The specific research work and conclusions are as follows:(1)The basic physical parameters of tailing mud were determined through basic laboratory tests.The influence of pressure filtration on the permeability coefficient of tail mud is discussed through osmotic test.Based on the compression test,the influence of pressure filtration on the compression parameters of tailing mud was studied.It was found that the permeability coefficient of the tail mud after pressure filtration decreased by 13.09%～15.18%.The compression coefficient decreases by 4.00%～19.05%,and the compression modulus increases by 1.53%～21.81%.(2)Based on the conventional triaxial test,the effects of dry density,confining pressure and shear rate on the static characteristics of tail mud were analyzed under the experimental conditions of consolidation without drainage.It is found that the softening degree of tail mud decreases with the increase of confining pressure and dry density,while the softening degree increases with the increase of shear rate.The increase of dry density inhibits the pore water pressure,while the confining pressure and shear rate promote the pore water pressure.Both c andφ increase with the increase of shear rate.(3)Dynamic characteristics of tailing mud under different conditions were studied by using dynamic triaxial apparatus,and the effects of dry density and confining pressure on dynamic stress-strain relationship,liquefaction characteristics and dynamic pore pressure development of tailing mud were analyzed.It is found that with the increase of dry density and confining pressure,the maximum dynamic modulus increases and the maximum damping ratio decreases.Under the same test conditions,the increase of dry density inhibits the possibility of tailings liquefaction.When the dry density is more than 1.69 g/cm3,the liquefaction resistance increases rapidly.When the equivalent vibration order increases from N12 to N30,cd and φd of tailing mud decrease,cd decreased by 18%～21%,φd decreases by 16%～21%.High density and high confining pressure had a stronger inhibition effect on the increase of dynamic pore pressure ratio.The dynamic pore pressure development of tail mud was in line with the pore pressure model of Seed,and the fitting degree was high(4)With the help of scanning electron microscope,the particle arrangement structure and particle morphology distribution of tail mud and loess in the same area,as well as the difference of pore distribution of samples were analyzed from the microscopic point of view.The mineral composition and content of tailing mud were determined by X-ray diffraction test.It is found that the tail mud particles are closely arranged after pressure filtration,forming flocculent structure and aggregating into a small number of aggregates with regular shape.The total number of pores increased by 34.04%.The total area increased by 4.65%;There was no significant difference in mineral composition content.