Study On The Reasonable Stage Height Of Two-step Mining And Subsequent Backfilling For The Dip And Medium Thick Iron Orebody And Its Backfilling Material Proportioning

The exploration of mineral resources is one of the important fundamental industries ofthe national economy. According to the statistics,23%of the total deposit mining cases aredip medium thick orebody mining projects among the underground metal deposit mining inChina. With the increasing of mining depth, this proportion is likely to climb in the future.Dip medium thick orebody is one of the most difficult mining orebody types which have beengenerally accepted in the field of mining industry both home and abroad. Maojiazhai ironmine orebody I of Weifang Wanbao Mining Ltd is of this type. The two-step stage roommining and subsequent backfilling method was adopted by Wanbao Iron Mine in the initialphase. However, large area of hanging wall rock collapses which obstruct the ore removalpath during the mining process. In order to control the underground pressure and guaranteethe production security, the upward horizontal cut-and-fill stopping method was adoptedlately. But, there are also many disadvantages of this mining method, such as small miningstratification height, heavy backfilling preparation workload, frequent backstopping times,long cycle length, excessive working faces, sophisticated production security managementsituation, high mining cost, low efficiency, high labor strength, large dilution rate and severeresource waste etc.Based on the above backgrounds, experiments and numerical simulation of the upwardhorizontal cut-and-fill stopping process for Wanbao Iron Mine Orebody I are carried out inthis paper. By using the numerical simulation software FLAC (Fast Lagrangian Analysis ofContinua), the mining process of orebody has been studied, the distribution laws of plasticzone, maximum principle stress and the minimum principle stress are obtained. According tothe simulation results, the design of the stage height of upward horizontal cut-and-fill miningmethod has been optimized and the mining stage height has been determined. Then, thecomponent proportion, physical and mechanical properties of the backfilling materials havebeen investigated in depth. Through the experiments, the apparent denstiy, packing denstiyand the porosity as well as the distribution of particle size of the classified tailings areobtained. In addition, the compressive strengths of different concentrations under three c-tratios (ratios of cementitous material to tailings) of1:6,1:9and1:12are gained and variation laws of compressive strength of these concentrations and c-t ratios are compared.Furthermore, the variation trends between cementitous material consumption andconcentration, between slurry unit weight and concentration are analyzed. Based on theexperiment results, lists of backfilling material components which can be used in thebackfilling working site have been made.The research achievements of this paper will not only provide the crucial reference forWanbao Maojiazhai Iron Mine for solving difficult technical problems under the conditionsof complicated mining situations, but also improve the security and benefits of the company.Moreover, the research findings can enrich the studies and applications of complicatedmining and backfilling technology, enhance the resource utility and protect the ecologicalenvironment. It is also of great importance in making contributions to the studies of thesustainable and coordinated development of mining industry, enveronment protection,production security and the economy development.