Research On Underground Mining Method Under The Open-pit And Underground Mining Mode In Luotang Min

With the gradual depletion of shallow resources,a large number of open-pit mines have been in the stage of deep open-pit mining,and deep open-pit mining is faced with the problems of increasing technical difficulty in mining and low mining safety,so most deep open-pit mines choose to turn to underground mining.The selection of mining and the selection of stope structure parameters have a great influence on the stability of the upper slope of the underground orebody in the combined open pit and underground mining system.The Luodang Mine has transitioned from deep open-pit to underground combined mining.In this paper,the mining of underground ore body of the Luodang Mine is taken as the research object.According to the mining technical conditions of Luodang Mine,engineering design,theoretical calculation and numerical simulation are used to study the underground mining methods and the structural parameters of mining stope.And the stability of the upper exposed slope of the underground mining area of Luodang Mine is also analyzed.(1)The two-step sublevel open stope followed by filling continuous mining method is proposed to solve the problem of high loss rate and high mining-cutting ratio in the original single-step sublevel open stope followed by filling mining method used in underground mining of medium to thick orebody in Luodang Mine.(2)According to the actual situation of Luodang Mine and the characteristics of the roof structure,the stope structure parameters of the two-step sublevel open stope followed by filling continuous mining method are designed based on the thin plate theory.The optimal width of the first step mining room is 12m,and the optimal width of the second step mining room is 18m.The maximum length of the mining room is 70m,and the maximum exposed area of the roof is 1260m~2.(3)Uniaxial compressive strength,tensile strength,and shear strength tests were conducted on the graded tailings cemented filling body of Luodang Mine.The mechanical parameters of the filling body,such as uniaxial compressive strength,elastic modulus,Poisson’s ratio,tensile strength,cohesion,and internal friction angle,were measured under different ratio conditions.Through the analysis of experimental data,the variation patterns of the mechanical parameters of each filling body with the amount of cement added and the mass concentration of the slurry were obtained.(4)According to the selection results of stope structure parameters and ore body occurrence conditions,the underground mining area of Luodang Mine is planned and designed,and the numerical model of open-pit to underground mining of Luodang Mine is established.Combined with the mechanical test results of backfill mass,the numerical simulation results show that the design of stope structure parameters is reasonable,and the stope and slope stability are good.(5)Applying the design results of stope structure parameters to the industrial test results show that the stability of roof and open-pit slope of stope with two-step sublevel open stope followed by filling continuous mining method is good;At the same time,the mining loss rate and dilution rate are all less than 10%.Compared with the original sublevel open stope subsequent filling method in Luodang Mine,the economic and technical indexes are superior,and the mining loss rate is lower.