With the increasing attention on the environmental protection of resource development and the strict requirements for the discharge of waste rocks，tailings，waste residues and other wastes generated in resource development，it is particularly important to dispose these wastes.The mixed filling of waste rocks and tailings is the most effective way to solve the discharge of mine waste.Taking the underground filling of Gaofeng mine as an example，It is necessary to determine the optimal ratio of waste rock and tailings mixed filling materials.The particle size of tailings and waste rock were analyzed by laser method and sieve method.The chemical composition of waste rock and tailings was obtained by X-ray spectrometry.The orthogonal experiment with four factors and four levels was designed，and the range analysis of the experimental data was carried out.The primary and secondary factors affecting the strength of filling body，slurry bleeding rate and slurry slump were explored，and the filling material ratio that preliminarily met the requirements of the mine was obtained.The slurry concentration is 83%，the ash sand ratio is 0.25，the waste tail ratio is 1.5 and the amount of pumping agent is 0.5%.According to the experimental data，the quadratic polynomial regression model of 28 d filling body strength，slurry bleeding rate and slump was established.The theoretical value and experimental value of the regression model were compared and analyzed.It is found that the relative error is within a reasonable range，indicating that the model has certain reliability for the prediction of filling body performance.Multi-objective optimization Pareto solution set obtained based on NSGA-II algorithm.The mixture ratio of waste rock and tailings filling slurry with good performance and lowest cost was determined.The results are as follows：According to range analysis，The ratio of ash to sand has the greatest influence on the strength of filling body，and the influence of slurry concentration，waste tail ratio and pumping agent decreases in turn.The ash sand ratio has obvious control effect on the slurry bleeding rate，and the waste tail ratio，slurry concentration and pumping agent effect decrease in turn.The slurry concentration has the greatest influence on slump，and the influence of pumping agent，ash sand ratio and waste tail ratio decreases in turn.Without increasing the cost of additional materials，the proportion of waste rock can be appropriately increased to improve the strength of the filling body.The cost of filling material for the optimized scheme is reduced by 2.9% compared with the preliminary scheme determined by orthogonal test，the optimized filling ratio is slurry concentration 82.989%，ash sand ratio 0.240，waste tail ratio 1.419 and pumping agent 0.537%.

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