Research On Method Of Determining Impact Radius Of Hydraulic Punching

At present,hydraulic punching is one of the important measures to prevent outburst in the area of pressure relief and permeability increase of coal seam in mines.Determining the parameters of influencing radius of gas extraction by punching borehole is of great practical significance for improving gas extraction efficiency,eliminating blank belt between the distribution holes and ensuring safety of coal mine.Combine the shortcomings of existing measuring methods,based on the analysis of hydraulic punching on the anti-outburst theory of mine coal seam,study and analyze the influence of looseness of coal around the borehole on gas emission.Discharge borehole gas flow,outflow and discharge limit discharge characteristics of drilling hole gas under negative pressure extraction,according to the sectional nature of gas emission from discharging borehole,Under the influence of negative pressure extraction,the abrupt change of gas emission attenuation coefficient of drainage hole and the difference of limit gas emission between drainage hole under the influence of negative pressure extraction and drainage hole without influence of extraction are discussed.A method for determining the influence radius of hydraulic punching extraction by means of gas emission attenuation characteristics is put forward.Field test has been carried out in Zhongtai Mine in Hebi by this method.The results show that the extraction time is 60 days,the non-punched borehole is drilled,the impact radius of extraction is 3.2m,the average coal discharge of punched borehole is 0.5t/m,0.9t/m and 1.3t/m,and the impact radius of extraction is 4.0m,4.7m and 5.1m respectively.It is concluded that the average coal discharge per meter of punched borehole is linearly related to the impact radius of extraction.Fitting equation:y₁=1.49x₁+3.32（x₁≤1.3）.Due to the limitation of field test analysis,a numerical model is established according to the coal seam condition at the site of field test and the numerical simulation is carried out.The results show that the maximum displacement of coal body and pressure relief radius are positively related to the pore size.The relationship between pressure relief radius corresponding to different hole enlargement diameters and different unloading quantity from field test and impact radius of extraction is consistent.Considering comprehensively that the suitable unloading quantity for hydraulic punching of Hebi Zhongtai Mine is0.9t/m,it is proposed that 6.5m×6.5m hole spacing.Based on this,the hydraulic punching extraction scheme for cross-layer drilling in Hebi Zhongtai Mine is optimized to improve the extraction effect.It can provide certain reference for determining the influence radius of hydraulic punching extraction in the same or similar coal seams.