Sedimentary Consolidation Characteristics Of Tailings In Kafang Tailings Reservoir And Stability Of Tailings Dam

Kafang tailings reservoir in Gejiu,Yunnan Province is a typical flat tailings reservoir with long accumulation time and complicated consolidation law.The tailings pond uses slag treatment technology to harden the beach surface of the reservoir area.There are more than 30 similar tailings reservoirs managed and used by Yunxi Tin Group in Gejiu area of Yunnan Province,and the Kafang tailings reservoir is the first large-scale tailings reservoir to apply the technology of beach slag treatment,which has strong demonstration significance for the scientific research of Kafang tailings reservoir.This paper takes Kafang tailings pond as the research object,through conventional physical and mechanical tests,new leaching consolidation tests,combined with SEM scanning electron microscopy,chemical element analysis and other advanced test means,makes a comprehensive study of its complex sedimentary consolidation law,the impact of slag treatment on the physical and mechanical properties of tailings and dam stability,and draws the following conclusions:（1）The tailings deposited in the Kafang tailings reservoir under the annular drawing mode are coarse and fine in front of the dam horizontally,and there are many fine accumulation layers,interbedded layers and interbedded layers in the middle of the dam.Vertically,the tailings are thick and thin,and there are many fan-shaped"sugar core"weak interbeds.At the same time,due to the difference of ore dressing technology before and after,the tailings show shallow Sulfide Tailings vertically.Silt placer and deep layer are the temporal characteristics of early oxidized tailings.（2）The strength of leaching consolidation is positively correlated with leaching time,leaching flow rate and chemical composition of leachate.In the process of leaching,because of the tension of water film between particles,the tailings first expand and rebound,then shrink and settle,the tailings become dense and the mechanical properties become better.（3）According to the analysis of tailings’microstructure,chemical elements and hydrochemical field,the strength zones of chemical consolidation are obtained.Area I（between dry beach and infiltration line）is a strengthening zone of chemical consolidation,and there are more colloidal clusters of Fe（OH）₃,Al（OH）₃ and As（As）among tailings particles;Area II（between slope and infiltration line）is a stable zone of chemical consolidation,with strong early chemical consolidation.At present,the properties of tailings cements are stable;area III（below the infiltration line）is the weakening area of chemical consolidation,and the content of cements is less.（4）Surface tailings with the influence depth of beach slag in the range of 0-2m are studied.Coupled weight analysis model of slag load and consolidation is established to quantify the change of mechanical indexes.The slag treatment destroys the intergranular structure of the surface tailings and increases the additional stress of the surface tailings,promotes the dissipation of pore water pressure,makes the water in the tailings easy to evaporate and discharges,and accelerates the drainage and consolidation of the surface tailings,which is the reason for the improvement of the physical and mechanical properties of the tailings.（5）By comparing the stability of the Kafang tailings dam with different methods and different periods,it is proved that the physical and mechanical properties of the tailings are improved with the passage of time,and the stability of the tailings dam is improved.The plastic region of the calculated results appears at the junction of weak interlayer or different rock and soil layers,which should be paid enough attention to.