Abstract: In order to reasonably set the size of shaft safety pillar in filling mining of hard rock deposit,considering the quality grade of hard wall rock and its own deformation and failure resistance,a combined shaft safety pillar retaining scheme is proposed on the basis of the conventional rock movement angle delineation method. Based on the study background of overlying resource mining in the east main shaft of an iron mine in Shandong Province,the engineering geological zoning and rock mass quality grade evaluation are carried out through field investigation and rock mechanics test. According to the classification results,for the surrounding rocks with quality ratings of class Ⅱ ~ Ⅳ above -250 m,the blockage shape safety ore pillars were delineated by movement angle of rock layers. For the harder rock masses rated as grade -250 m,cylindrical safety pillars were defined with a maximum distance of 80 m from the shaft centerline. In addition,two backfill mining schemes for shaft overlaying resources were designed,that is,the post-filling mining with shallow boreholes and the upward horizontal layered backfill mining. The study results indicated that the displacement of inner shaft walls of the upward horizontal layered backfill mining was 80% that of the post-filling mining with shallow boreholes. However,the shaft deformation caused by the two mining schemes did not exceed the safety standard. The proposed mining scheme of the upward horizontal layered backfill mining and combined shaft safety pillar retaining scheme have been successfully applied in the mine,and the recovered ore volume is about 4 million t,which can provide reference for the mining operation of wellbore overlaying resources in other similar mines.

Key words: fill mining,hard rock deposit,safety pillar in shaft,rock mass quality classification,numerical simulation