Study on optimization of coal pillar width of gob-side entry driving in thick coal seam with gas outburst

In the mining of outburst coal seams,there are problems such as excessive coal pillars left over during mining and huge investment in outburst prevention and elimination,which is different from the concept of coal mining at the present stage.Reasonable coal pillar width and safe roadway layout can not only ensure the reasonable and safe mining of coal,but also improve the recovery rate of coal resources and reduce the investment input and outburst prevention and elimination in outburst coal seams.Taking No.1 upper coal No.230102 working face of Xinji No.2 Coal Mine as the research object,the stress distribution law of adjacent empty coal body and the width range of limit equilibrium zone in the process of coal seam mining are obtained by theoretical analysis and calculation; The variation of vertical stress in adjacent empty coal body during coal seam mining was measured by borehole dynamometer,combined with numerical simulation of working face advancement and verification of gas content in adjacent empty coal body and the coal body on both sides of the entity,and then the influence range of mining pressure relief in outburst thick coal seam was determined; Based on FLAC3D software,the roadway excavation under different coal pillar sizes was simulated,and the reasonable coal pillar width was determined in combination with the pressure relief range and the issues concerned in engineering practice.The research results show that:① with the continuous advancement of the working face,the bearing stress in the coal body adjacent to the working face increases to the peak value first and then decreases to the original rock stress level with the increase of the depth from the gob,and the peak value of the supporting stress will appear near 9.18 m; ② In the mining of outburst thick coal seam,the adjacent empty coal body 0-25 m is the pressure relief affected area,and its pressure relief area and plastic area are the range of 0-9.5 m of adjacent empty coal body; ③ When the coal pillar is 7-9 m,it can improve the coal resource recovery rate of outburst thick coal seam,achieve the purpose of coal pillar stability and easy support,and reduce the amount of outburst elimination of roadway excavation along the gob in outburst thick coal seam,which is conducive to the control of roadway surrounding rock and ensure safe production.