Reasonable location for gob side roadways in an extra-thick outburst coal seam under upper protective seam mining
Based on the gas geological conditions of the extra-thick coal seam under the upper protective seam mining,comprehensive theoretical analysis,numerical simulation,engineering practice and other methods were used to study the distribution characteristics of lateral stress in the goaf,the variation law of outburst risk prediction indicators,and the reasonable location of the goaf roadway.The results indicate that there is a stress recovery effect in the fractured rock after the upper protective layer mining,and after the stress recovery,the peak lateral stress in the goaf will move towards the goaf;Based on the test results of coal outburst prediction indicators at different distances from the side of the goaf,it was divided into sufficient pressure relief discharge area,effective pressure relief discharge area,and hazardous area.Combining with engineering analogy,numerical simulation results,and the need to isolate gas in the goaf,coal pillars were laid along the goaf with a width of 5～7 m;After adjustment,the maximum values of outburst prediction indicators and air return gas concentration during tunneling were respectively 0.16 mL/(g·min1/2)and 0.22%,with a decrease of 66%and 35.3%compared to that before adjusted,which ensured the safety of roadway development and verified the rationality of retaining coal pillars along the goaf.
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