| The tailing material and the unique engineering properties of the tailings make the normal operation of the tailings reservoir dependent on the stability of the dam body.Therefore,it's necessary to study the sedimentary rules and safe operating conditions of the tailings pond in order to solve the stability problem of the tailings dam.There are many factors affecting the stable operation of tailings dams,including mainly the particle composition of the tailings,the form of the dam body,the sedimentary characteristics of the tailings in the dam,the shear strength of tailings,the slope and height of the dam,and the dam.Body immersion depth,dry beach length and so on.The paper relies on the actual project of high pile of phosphogypsum tailings dam in Wujiayu,Yunnan.The physical and mechanical properties of tailings,seepage law of tailings dam,static and dynamic stability and reliability of tailings dam,seismic response and liquefaction characteristics of tailings dam,tailings dam The key technologies for expansion and reinforcement were further studied.The main contents of the dissertation and the results achieved are as follows:(1)Based on the engineering geology and hydrogeological investigation data of the Wujiabu phosphogypsum tailings dam,field tests were conducted in the tailings area,and the main tailings were tested for static and dynamic characteristics.Based on the field test results and laboratory test results,the depositional laws and physical and mechanical properties of phosphogypsum tailings were studied.(2)Based on the saturated-unsaturated permeability characteristics of the tailings and their shear strength theory,combined with the fluid-structure interaction mechanism in the tailings dam,the finite pore analysis software Midas-GTS and Geo-Studio are used to analyze the pore water pressure of the tailings dam.Distribution characteristics and distribution characteristics of seepage field.(3)Based on the seepage calculation,the static stability of the tailings dam under different working conditions is calculated by using the limit equilibrium method and strength reduction method,and the seepage effect and coupling effect of the different dry beach lengths are studied.At the same time,the theory of reliability is introduced on the basis of the theory of limit equilibrium.Through the sensitivity analysis and reliability analysis,the influence of the variability of each variable on the reliability of the tailings dam stability is studied.(4)Using the two & three-dimensional finite element dynamic calculation model of the tailing dam to select reasonable parameters,boundary conditions and constitutive model of the tailings dam,analyze the distribution characteristics and dynamic response of the stress-strain field before and after the expansion of the tailing dam.Characteristics and seismic liquefaction characteristics,and comprehensive evaluation of dynamic stability of the tailings dam under seismic conditions.(5)Based on the analysis results of the static and dynamic stability and reliability of the Wujiajing phosphogypsum tailings dam,combined with its engineering characteristics and experience in expanding and consolidating the tailings dam,the aseismic reinforcement effect of the expansion measures for the tailings dam was studied.The results show that various reinforcement measures can improve the static and dynamic stability and reliability of the tailings dam,and reduce the dynamic response and the possibility of initial liquefaction of the dam.Considering the difficulty of construction and the allowable cost of construction,it is recommended to use reverse pressure slope and anti-slide piles to reinforce the joint reinforcement measures.The main innovative research results of the thesis are mainly reflected in the following aspects:(1)By studying the water-soil characteristics curve and permeability function of phosphogypsum,the effect of matrix suction on unsaturated permeability is considered.The unsaturated properties of phosphogypsum are more accurately described,making the seepage field calculation results more in line with the actual situation.(2)Combine the safety factor method with the reliability analysis method,consider the variability of the dam's stability factors in time and space,and obtain the safety coefficient and corresponding reliability index of the potential sliding surface,so that it is more scientific And reasonably evaluate the stability of the tailings dam.(3)Initially determine the possibility of liquefaction of the tailings dam using the in-situ test method and shear stress comparison method,and perform finite element liquefaction calculation on the tailings dam to further analyze the possibility of liquefaction of the tailings dam and liquefaction sites.,And comprehensive evaluation of the impact of liquefaction on the stability of the dam. |
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