Study On The Range Of Coal Seam Outburst In The Direction Of The Goaf Under The Coal Seam In Hongyan Coal Mine

In order to study the outburst range of the coal seam under the inclined direction of the coal-free mining goaf,the coal-body blasting deformation theory,mine pressure theory,coal seam gas flow-solid Based on the theory of coupling,laboratory physical similarity simulation test,numerical calculation and on-site investigation is carried out to develop the lower part of the goaf after the inclined working face of the 6# coal seam of Hongyan Coal Mine The study on the occurrence law of coal seam gas and the size of the outburst is to provide a basis for determining whether the wind tunnel area of the lower section needs to be additionally arranged for the strip drainage.The main research results are as follows:(1)From the physical and mechanical tests of rock specimens,the mechanical properties of uniaxial compressive strength,tensile strength,cohesion and internal friction angle of different layer rock specimens are obtained.(2)After the upper section of the goaf is formed,the direct roof collapses,and the coal seams show obvious cracks and develop upwards.After a period of time,the newly created crack width becomes smaller and smaller until it closes.The coal seams in the lower section also have different degrees of displacement deformation.The coal and rock mass near the goaf is strained,and the coal body may undergo expansion and deformation,which provides good conditions for gas desorption and diffusion along the coal.And due to the influence of mining,the stress balance of the lower section coal seam is redistributed after failure,and the stress peak appears near the position of 20cm(corresponding to the field 20m)from the goaf.(3)Strain and gas pressure of inclined coal body is carried out.The study shows that with the mining of the upper section of the coal seam,the original equilibrium stress field of the lower section of the coal seam is destroyed,the peak stress propagates to the lower part of the coal seam,and stress concentration occurs near 17 m from the goaf.Due to the influence of mining,the gas occurrence state along the empty coal body changes,the gas adsorbed in the coal body gradually changes to a free state,and the coal body near the goaf position has the highest permeability,which is 6.5e-17 m2,desorbed gas.Gradually spread to the goaf,the gas pressure along the empty coal body decreases,and the extent of the outburst gradually expands with time.The numerical results show that as the boundary distance of the goaf increases,the rate of residual gas pressure drop in the coal seam is slower and nonlinear.When the distance exceeds 25 m,the time required for the residual gas pressure of the coal seam to reach the standard will be greatly extended.(4)Before and after the mining of the upper section of the 6# coal seam in Hongyan Coal Mine,the gas pressure and gas content in the research area of the lower section coal seam were investigated on site.It is found that after 500 days of working face mining,the residual gas content of the lower section coal seam within 25 m from the goaf is less than 8m3/t;the gas pressure has also decreased to different extents,15 m away from the goaf,gas pressure From 3.1 MPa to 1.5 MPa,the gas pressure dropped from 2.8 MPa to 1.9 MPa from the position of 25 m in the goaf,both greater than 0.74 MPa.The fitting analysis of the observation data shows that the gas pressure of the borehole at different distances from the goaf changes linearly with time.According to the regression equation,it is estimated that after about 770 days of mining in the upper section,15 m away from the gob.The gas pressure of the borehole will be reduced to below 0.74 MPa,and the gas pressure at the location 25 m from the boundary of the goaf has remained basically stable.The residual gas content and residual gas pressure in the corresponding area after 2-3 years of mining in the adjacent section were measured.The results show that the residual gas content is less than 8m3/t.This shows that the gas emission from the coal in the lower part of the goaf is a discharge process that is greatly affected by time.