Study On Feasibility Of Phosphorus Tailing Based Cemented Backfill And Its Environmental Impact

Phosphorus tailings are wastes generated during phosphate ore mining,which occupy land resources in long-term stockpiles and cause serious environmental pollution at the same time.In order to protect the environment,to reuse of solid waste,and to ensure the stability of the mine,this paper selects phosphorus tailings as filling aggregate,cement and fly ash as cementitious materials to make phosphorus tailings cemented backfill,and conducts research on the static mechanical properties,dynamic mechanical properties and environmental impact of phosphorus tailings cemented backfill.By setting different mass concentrations of filling slurry,cement to aggregate ratio and conducting orthogonal tests,the effects of different factors on the mechanical properties and environment of phosphorus tailings cemented backfill were investigated in detail.The main research results and outcomes are as follows:(1)The mass concentration of the filling slurry has an important influence on the properties of both the filling slurry and the backfill.When the aggregate-cement ratio is the same,the uniaxial compressive strength of the backfill increases with the increase of the slurry mass concentration,the initial and final setting time is shortened accordingly,and the dynamic compressive strength increases when the average strain rate is similar.(2)Aggregate-cement ratio has an important influence on the properties of both the filling slurry and backfill.At the same slurry concentration,as the percentage of cementitious agent increases,the water secretion rate and the initial and final setting time of the filling slurry decrease accordingly,and the uniaxial compressive strength of the backfill increases,and the dynamic compressive strength increases when the average strain rate is similar;while as cement is replaced by fly ash,the water secretion rate of the filling slurry increases,the initial and final setting time increases,and the uniaxial compressive strength of the backfill decreases when cement is used as the cementitious agent.(3)Through designing the three-factor orthogonal test of slurry concentration,mixing time and proportion,the effects of the above factors on the experimental indexes such as filling slurry performance,static mechanical properties of backfill and underground water environment were determined,and the significant degree of each factor on the experimental indexes was also obtained through ANOVA.The optimum filling slurry preparation conditions suitable for underground filling were determined by considering the actual requirements of the mine.(4)By analyzing the phosphorus tailing based cemented backfill,the filling slurry and 28 d toxic leachate of the backfill,it was found that the phosphorus tailing based cemented backfill had good solidification ability for phosphorus and fluoride ions,and the addition of fly ash could reduce the p H in the toxic leachate of the backfill.