Study on the Influence of Coal Pillar on the Pressure Relief and Outburst Elimination of the Upper Protective Layer Mining

In view of the unfavorable influence of the special coal pillars on the mining effect during the mining of the upper protective layer, taking Qingdong Coal Mine in Huaibei as the engineering background, the influence of coal pillar on the mining effect of upper protective layer was studied by theoretical analysis, numerical simulation and field measurement. The theoretical analysis showed that there is a blind zone below the coal pillars; the spatial and temporal variation of stress and displacement of coal body in the mining process on upper protective layer were analyzed by numerical simulation, under the condition that coal pillars reserveed different widths, it was concluded that the mining of the upper protective layer will cause the discontinuity of the protective area when pillars were reserved, and the wider the pillar, the more obvious the effect on the upper protective layer; the two indexes of coal seam permeability coefficient and drilling cuttings in the area affected by coal pillar in 8210 working face of Qingdong Coal Mine were measured, it was concluded that when coal pillars with different widths are set in overlying the 7th coal seam, there will be potential outburst risk areas in the 8th coal seam below the coal pillar, the results of numerical simulation analysis were validated by field measurement.