Study On Rules Of Aggregate Structure Evolution And Mud Densification During Unclassified Tailings Thickening

Full tailings paste backfilling is the fundamental development direction of green mining,and thickening is one of the essential process of full tailings paste backfilling technology,which directly affects the system operation and backfilling performance.Based on the structure evolution characteristics of aggregate and the rules of channelling formation and distribution,this thesis focus on permeability and compressibility which represent the full tailings dewatering performance.The completed works mainly includes:(1)The influencing factors of flocculation and settling performance were studied,SEM images of aggregates during batch settling were obtained,and the fractal characteristics of aggregate structure were studied.Based on the SEM images analyze,the relationship between fractal characteristics and aggregate structure during settling was established.Water in the networked mud bed has been classified into 4 types,which are free water,pore water,capillary water and hydrated water.The exponential function between water concentration by weight and porosity of aggregate was established.(2)FBRM and PVM real-time on-line and in-situ monitoring of the aggregate structure during thickening was taken,the correlation of aggregate structure evolution phases characteristics and the degree of aggregate breakage was investigated.Based on the chord length,counts distribution and real-time micrograph of the aggregates during compressive dewatering of the full tailings,the shearing effects on the aggregates structure and strength was analyzed.The evolution of aggregates structure during compression dewatering of the full tailings was divided into 3 phases:growth,reconstruction and breakage.(3)The distribution rules and duration characteristics of the channelling during the full tailings compressive dewatering process were investigated,base on solid volume fraction,the function of effective stress was proposed.The correlation mechanism between the channelling and excess pore water pressure was established,the structural characteristics of the stable and unstable channelling were defined,and the distribution rules and duration characteristics of channelling in the mud were clarified.Based on the transformation of effective stress and excess pore water pressure,the power function relationship between effective stress and solid volume fraction of slurry was established.(4)The desification degree of aggregate was analyzed,the influence of shear rate and initial mud bed height on full tailings thickening performance was developed,and the function of solid flux density was established.The characterization framework of mud bed permeability with effective hindered settling function and permeability coefficient,and the characterization framework of mud bed compressibility with solid diffusion coefficient and consolidation coefficient were formed.The function of solid flux density during the full tailings thickening was established,and the influence of shear rate and initial mud bed height on the full tailings thickening performance was quantitatively analyzed.(5)Based on solid flux density,the steady-state operation conditions and dewatering efficiency of the paste thickener were analyzed,the correlation between rake torque and concentration of the mud layer was established,and the reasonable operation strategy for the paste thickener was proposed.The solid flux,steady-state operation conditions and unit area dewatering capacity of the paste thickener for a copper mine were analyzed.The mathematical model of rake torque coupling the yield stress of different mud bed height was formed,as well as the mathematical model of rake torque under different concentration and shear rate were established through CFD numerical simulation,and reasonable operation strategy for the paste thickener was proposed.