| Aiming at the problem that it is difficult to predict the outburst elimination effect of the protected layer in the influence area of the coal pillar in the retained area of the protective layer in the sixth coal mine of Pingdingshan No.6 Coal Mine,taking the Wu 9-10-22290 working face and the corresponding Wu 8 protective layer coal pillar as the research object,the stability,influence range and plastic zone of the coal pillar are determined by theoretical calculation,and the stress state of the coal pillar with different widths and the distribution mining of the Wu 9-10-22290 working face are numerically simulated.Combined with the field test,the following conclusions are drawn :(1)The stress of the floor rock under the coal pillar.The peak value of the curve is concentrated at the center line of the coal pillar.The stress decreases sharply near the edge of the coal pillar,and the farther the distance is,the gentler it tends to be.Under the coal pillar,on the sections of different depths,the smaller the vertical distance is,the greater the stress value is,the greater the stress influence is,but the influence range is relatively small.At the same depth section,within the width of 4 ～14m,the larger the width of the coal pillar is,the greater the influence range of the floor rock is,and the greater the stress peak at the coal pillar is.(2)Taking Pingmei No.6 Coal Mine as an example,according to the stress analysis,the width of the plastic zone of the remaining coal pillar in the No.8 coal seam is 15.8m,which is greater than the width of the 4m coal pillar,indicating that the coal pillar is in a plastic deformation state as a whole.The stability safety factor of the coal pillar is 0.46 < 1.5,and the coal pillar cannot maintain long-term stability.The theoretical maximum influence range of the remaining coal pillars on the tendency is 10.42 m.(3)The measured values of q value and S value are 1.18 L / min and 4.12 kg / m in the coal pillar affected area,respectively,which are less than the critical values of5.0 L / min and 6.0 kg / m;the measured value of the residual gas content measured with the advance of the mining face is 1.725m3 / t ～ 2.084m3 / t,and the corresponding gas release rate is 53.6 % at the minimum and 63.2 % at the maximum,and the coal seam gas content is effectively released.The maximum height of the remaining coal pillar is 1.2m,the range of the coal pillar is greater than 4m,and the height of the remaining coal pillar is only 54 % of the height of the original coal pillar.(4)The 4m wide coal pillar left by the No.8 coal seam is in the state of plastic penetration,and the depth of stress concentration is 8m.The stress in the affected area of the protected coal pillar is 12.7 ～ 27.5MPa at 12 m below the coal pillar.The maximum stress value in this area is 42 % of the stress of the coal pillar,so there is no obvious stress concentration phenomenon in the affected area of the protected coal pillar.In the vertical direction,the coal strata in the range of 33 m above the protective layer and 28 m below the protective layer are in the plastic zone,and the protected layer is in this range.The gas can be effectively released through the cracks,and the working face of the protected layer in the coal pillar affected area can be safely mined.The paper has 49 figures,10 tables,and 76 references. |
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