Study on the width of stress-relaxed area for pressure-relief of outburst coal seam in gob-side entry driving

The Rules for the Prevention and Control of Coal and Gas outburst state that in a outburst coal seam, the spacing between the coal drift and the coal should exceed 20 m at the pressure-relief and outburst elimination boundary. In order to explore the width of stress-relaxed area for pressure-relief of near horizontal outburst coal seam in gob-side entry driving, the residual gas pressure and gas content of coal mass in pressure-relief and outburst elimination zone were measured. Combined with the numerical simulation results of the width of stress-relaxed area of coal beside the roadway in the mining process, the prediction model of the width of stress-relaxed area of coal winning in the working face under different space-time conditions was established. It is found that the residual gas pressure and gas content in the transition area from the pressure-relief and outburst elimination zone to the stress-concentrated area increases sharply. Based on the measured data of residual gas pressure and gas content of coal mass in pressure-relief and outburst elimination zone of outburst coal seam in Chengjiao Coal Mine, Henan Province, it is confirmed by numerical simulation that when the stoping face is advanced to 500 m and the roadway is driven for about 330 d, the width of stress-relaxed area of coal beside the coal drift at the final mining line is at least 35 m. This is in line with requirements of outburst elimination of coal drift driving in The Rules for the Prevention and Control of Coal and Gas outburst, and 5 m coal pillar can be reserved in the gob-side entry driving. The research results can provide a theoretical reference for the determination of width of narrow coal pillar in the gob-side entry driving and the lay out of gob-side entry driving in outburst elimination range in stress-relaxed area.