Research On The Optimization Of Mining Methods For Steeply Inclined Medium-thick Orebodies In The 460m Mining Area Of Jiangfeng Iron Mine

The orebody,with a buried depth of 270～150m,in the 460m mining area of the Section Ⅱ of Jiangfeng iron mine occurs in 460～520m above sea level.The orebody is with simple morphology,and is dominated by magnetic iron.The occurrence of the orebody is similar to that of strata,with a dip direction of 105°～162°,a dip angle of 74°～90°,and a single engineering orebody thickness of 0.8m～18.65m,indicating that it is a steeply inclined thin to medium-thick orebody.Taking the steeply inclined medium-thick orebody in the 460m mining area of the Section Ⅱ of the Jiangfeng iron mine as the research object,the mining technology evaluation,on the basis of field investigation and data collection,was carried out.Three mining methods were preliminarily selected,i.e.sublevel open-stoping with delayed backfilling,mechanical point-pillar upward horizontal cut-and-fill stoping,and upward horizontal drift-and-fill stoping.Through process analysis,cost calculation,and economic comparison,the sublevel open-stoping with delayed backfilling method was finally selected as the mining method for the 460m mining area of the Section Ⅱ.According to the orebody thickness and the stability of the surrounding rock roof,in order to control the exposed area of the roof and side walls,referring to the previous mining experience,the possible mine chamber lengths（15m,25m,35m,45m）were initially selected.The Mathews stability graphic method was used to calculate the limit span and the limit exposure area under stable state and caving state when the mine chamber length is 15m,25m,35m,and 45m.Using FLAC^3D software to simulate the results of the orthogonal test,it was concluded that the length of the mine room chamber should not exceed 35m.Considering the reasonable exposed area of the orebody roof and side walls,the mine chamber length was determined as35m.According to the simulation calculation results,when the length of the mine chamber is35m,the displacement of the ground surface and the pillar gradually decreases with the pillar size increasing from 4m to 8m,while the displacement changes little with the pillar size increasing from 8m to 10m.In order to protect the rubber forest on the surface,the appropriate size of the pillar was finally determined to be 8m.According to the selected mining method and the determined structure parameters of the stope,an industrial test was carried out on stope（1）in the 460m level of the 460m mining area of the Section Ⅱ.Judging from the stability of the surrounding rock of the mine revealed by the test,the structure parameters of the sublevel open-stoping with delayed backfilling method can realize the stoping and meet the requirements of mining and filling,indicating that the selected mining method and structure parameters are reasonable and feasible.This mining method optimization study provides guidance and practical experience for the determination of deep mining methods.