Research On Multi-Solid Waste Collaborative Comprehensive Utilization Of Mining Backfill In Jinchuan Mine

Chinese government has gradually attached importance to environmental protection.The use of solid waste in backfill of mining has become an inevitable choice for resource security,environmental protection and economic development.Jinchuan Nickel Mine faced with high ground stress and broken surrounding rock,the downward stratified approach was used to backfill the mine.High-density and high-strength backfilling technology with rod-sand aggregate and cement not only leads to mining backfilling costs as high as 157 yuan per cubic meter,but also leads to a large anount of waste rock,tailings and metallurgical slags.The resource utilization of waste in Jinchuan Mine is the only way to reduce mining cost and achieve waste-free green mining.In view of the backfill problems about rod sands and cement existing in Jinchuan Mine,the way of alkali salt composite was used to stimulate the potential activity of metallurgical salg in this paper.And then a kind of low-cost early-strength backfilling cementitious material was developed,it could be suitable for waste rock mixed aggregate.Researches on the synergy and comprehensive utilization of solid waste resources were carried out,such as waste rock and metallurgical slag.Researches were carried out through lab tests,theoretical analysis and industrial test,and main results were obtained as follows:(I)GGBS and many kinds of solid wastes were used as main raw materials,through physical chemical excitation and solid waste synergy,a new backfilling material was prepared,which could not only replace cement-bonded sand and gravel for mining backfilling in Jinchuan Mine,but also reduce backfilling cost and realize solid-waste utilization.(2)Based on microscopic test analysis such as X-ray and scanning electron microscopy,it was confirmed that the main hydration products of the backfilling material were composed of ettringite,calcite,C-S-H,calcium alumina feldspar and calcium sulfate.Among them,the hydration products that contribute mainly to the strength of the less-clinker backfilling materials are ettringite,C-S-H and calcium alumina feldspar,while the hydration products that contribute mainly to the strength of the mass-clinker backfilling materials are ettringite and C-S-H.(3)Through the chemical excitation test,it was found that the strength of the sample decreased with the increase of the amount of substitution of steel slag,when the substitution amount of steel slag was in the range of 10%to 20%,it helped to improve the late strength of the sample.The greater the fly ash content,the greater the contribution to the later strength,and the greater the early strength loss.With the increase of gypsum content,the strength rule of backfilling materials at all ages first increased and then decreased.(4)Considering that the 3d strength of Jinchuan Nickel Mine must not less than 1.5MPa,this study considered that the clinker,gypsum,mirabilite and GGBS content should be 3:5:1:90,under the condition of cementitious materials with a specific surface area of 431m2/kg.In this way,this study could meet the strength requirements of backfilling in Jinchuan Mine.(5)Waste rock below 12mm and copper tailing slag were used as aggregates,and cement was used to prepare backfilling materials.Under the same aggregate bulk volume,the strength of the sample increased with the increase of cement content.Under the same content of cement,the larger the proportion of waste rock in the aggregate,the higher the strength of the sample.(6)By using the orthogonal experiment synergy BP neural network model for the training of compressive strength of backfilling material samples in Jinchuan Nickel Mine,the BP neural network prediction model of 4 × 9 × 2 structure was built,which could realize the prediction of compressive strength of backfilling samples in different ages,the relative error was within 5%,and it could meet the need of engineering.(7)The image method was used to collect the information of the cross-section of the aerated backfilling samples.The statistical calculation of Matlab can realize the characterization of the porosity,pore size distribution and average pore size of the macroscopic pores and mesoporous of the aerated backfilling samples.Reducing the fineness of the aluminum powder could reduce the size of the pores,but could not change the number of interconnected pores;and mixing the two kinds of fineness aluminum powder could effectively reduce the number of interconnected pores in aerated backfilling samples.(8)The image method was used to collect the information of the cross-section of the backfilling samples.The statistical calculation of Matlab can realize the characterization of stacking of aggregates of different diameters.The dis tribution of aggregates with>7.5mm could visually reflect the distribution of aggregates,which could provide guidance for industrial experiments.