| Aiming at the mining of the No.15 protective layer in the fourth mine of Pingmei Co.,Ltd.,the double section coal pillars with a width of 4.0m on both sides of the joint15-23160 and a distance between adjacent coal walls of 5.0m are left on the 16-17 protected layer.Research on the impact of protection protection scope.Through the ultimate load calculation,numerical simulation study,field test,and stress state analysis of the remaining double-section coal pillars,the following main conclusions are drawn:The stress limit load calculation result is that the limit load of the double section coal pillar left in the 15 th coal seam is 26.0 MPa;the numerical simulation result shows that among the double section coal pillars left over from the 15 coal seam,the concentrated stress on the shallow coal pillars is compared with that of the deep coal pillars The maximum concentrated stress of the large and shallow coal pillars appeared in the15-23140 and 15-23160 after the end of the mining.During the excavation of the16-17-23160 machine roadway,the maximum concentrated stress of the deep coal pillars appeared in the 16-17-23160 wind tunnel.After excavation,they reached 131.1MPa and85.1MPa respectively;after field tests,the amount of drill cuttings and residual gas content of the 16-17-23160 air tunnel were found to rise first and then decrease to a basically stable level.Trend,the maximum amount of drill cuttings measured in the test range is 3.7kg/m,which is less than the critical value of outburst risk of drill cuttings6.0kg/m;the maximum residual gas content measured in the test range is 2.63m3/t,and the coal seam gas content is effectively released,The released amount exceeds 50% of the original gas content and is less than the critical value of outburst hazard 8.0m3/t;16-17-23160 wind tunnel excavation face drilling cuttings and the measured value of the initial velocity of gas emission from the borehole side drill The hole(a)to the deep part of the coal body(c)continues to increase;the maximum initial gas emission velocity from the borehole is 2.1L/min,which is less than the critical value of outburst risk5.0L/min;the maximum amount of drill cuttings is 3.4kg/m,which is less than the outburst The critical value of danger is 6.0kg/m;the two 4.0m coal pillars left on both sides of the 15-23160 connecting lane,the maximum height of the original coal pillar is1.6m,and the maximum height of the residual coal pillar is 0.64 m,which is farther away from the original coal pillar.The height of the far residual coal pillar is lower.A comprehensive analysis of the above conclusions draws that: the two-section coal pillars left in the 15 th protective layer have been destroyed under the influence of the mining of the 15 th and 16-17 coal seams.There is no obvious stress concentration under the coal pillars,and the coal pillars in the protected layer are within the range of influence.The gas is effectively released,and the double-section coal pillar affected area also has a good pressure relief and permeability enhancement effect.The remaining double-section coal pillar has no effect on the delineation of the protection range of the protected layer,and the protection effect has continuity in tendency.The paper has 49 pictures,13 tables,and 89 references... |
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