Study on Pillar Mining Scheme of Gaofengshan Ore Section in Yunxi
In order to make the residual ore resources of Yunxi Old Factory Branch get better recycling,in view of the situation that there are a large number of residual pillars in the panel area of Gaofengshan ore section,after the completion of the on-site engineering geological investigation,representative rock samples were selected to conduct the rock mechanics test,and the result parameters were obtained.FLAC3D numerical simulation method was used to analyze the stability of the stope before the recovery of the pillars,and the law of ground pressure appearance in each panel area was obtained.Combined with the actual situation of the mine,it is concluded that the two methods of extracting the mining pillar and replacing the pillar are suitable for the recovery of the pillar in the mining area.On this basis,six pillar recovery schemes were considered under ideal conditions,and after comparative analysis,only the two-step collodion-filled room-and-pillar mining method is suitable for recovering the security ore in this mine.Through the filling mechanical parameter experiments,the filling body parameters required for two-step spaced back mining were derived after comparing multiple schemes.At the same time,the pillar recovery process was discussed in detail,and the industrial test of pillar recovery was carried out in areas with different degrees of geopressure manifestation.From the experimental results,the top plate of the pillar can be kept stable during and after the pillar recovery process.Based on the actual situation,the 13 pillars in the mining section were analyzed in terms of the resource grade of the pillars,the stability of the surrounding empty area,the need for protection works above the pillars,the economic benefits of mining and the price break-even.After the study,it is concluded that through the results of industrial test,the two-step cemented filling mining method with the specifications of 4 m×4 m can be used for the pillar mining,with the strength of one-step cemented filling is greater than 3.52 MPa and the strength of two-step filling is greater than 1.08 MPa.There are four pillars in the section with relatively intact,large amount of retained resources and high grade,which are in good condition for mining.The 4#pillar panel in the south plate area should be mined when the market metal price of tin concentrate is more than 244800 yuan/t.The remaining 3 ore pillars can be mined when the market metal price of tin concentrate is more than 100500 yuan/t.
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