Study On Gas Control Technology Of Goaf With Outside High Drilling Field

Taking XV1306 working face of Feng Huangshan mine as the research object,the gas emission from goaf of adjacent 9#coal seam accounts for 30%?50%of 15#coal seam gas emission.And 15#coal seam gas content is too large,the upper corner gas often overrun.influence mine safety production.Based on the analysis of the geological data of the XV1306 working face in Feng Huangshan mine,the paper puts forward the scheme of gas control with the near horizontal fan drilling hole in outside high drilling field.Based on the geological histogram of roof strata in XV1306 working face,the paper analyzes the overlying strata with combined rock beam theory and carries out three zone classification,9.82m thick K2 limestone is the caving zone,the fracture zone is connected with the 9#coal seam goaf which is 32m to 15#coal seam in vertical distance.Through FLAC3D numerical simulation study of goaf overburden development,overburden pressure were fully released when mine 110m along strike,and the failure pattern of the overlying strata along the coal seam tends presents "Hump" distribution,and is connected with the 9#coal seam goaf.Through numerical simulation of the plastic zone and vertical stress distribution of 10m,20m,30m,40m coal pillar on the layout of outside high drilling field,determines that the reasonable width of the coal pillar is about 30m and outside high drilling field is about 15m outside Return Lane.The development of overlying strata was detected by CXK6 borehole imaging instrument,which verified the correctness of theoretical analysis and numerical analysis,and the vertical distance of outside high drilling field to coal seam is determined to be 7?12m,and the vertical distance of the horizontal hole to coal seam is about 15m.Based on the work we have done,the governing equation of gas migration in goaf is established,the gas migration law of goaf is simulated with the using of the Fluent numerical simulation software under the condition that extraction isn't carried out and different pumping flow,the optimal drainage flow is 30m3/min?35m3/min.The engineering practice shows that:Main gas flow of outside high drilling field is in the range of 20m23min to 37m3/min,the gas drainage rate of the goaf is 1ore than 60%,and the gas concentration in the upper corner has been maintained under 0.8%.Outside high drilling field can significantly improve the coverage area of drilling,reduce the number of abandoned holes in the collapse of goaf,and improve the efficiency of extraction.