| In view of the characteristics of high adsorption and low permeability of coal seams in Xuehu Coal Mine,as well as the promble of the large amount of gas drainage engineering and poor effect of drilling and pumping,the use of bedding hydraulic line acupressure relief and permeation tech and nology makes the coal pores around the borehole.The development of fissures,improve the permeability of coal seams and gas drainage efficiency,achi eve the purpose of rapid and efficient extraction of coal seam gas and achieve the purpose of eliminating the standard,and the practical application of the bedding hydraulic line acupoint technology.In this paper,the combination of theoretical analysis,numerical simulation and field test verification is used to test and analyze the change of gas parameters and stress evolution of boreholes before and after the formation of hydraulic lines in 25040 working face,and to determine the effective influence of drilling holes in the bedding hydraulic line.The best technical parameters of the radius and hydraulic line forming points,and the effect of pressure relief and anti-reflection measures on the hydraulic line acupoints.The main research results of the thesis are as follows:(1)According to the occurrence conditions and engineering geological conditions of coal-bearing strata in 25040 working face,the three-dimensional numerical calculation analysis model was established by using COMSOL software,and the law of gas extraction time and effective influence radius of different caving line drilling holes was simulated and analyzed.The results show that the effective impact radius of the borehole gradually increases with the increase of the agglomeration time,but the effective growth radius increases continuously,and the reasonable extraction time of the line acupoint is determined.For 90 days;the effective influence radius of the line augmentation hole increases with the increase of coal output,but its growth rate first rises and then decreases with the increase of coal output.Finally,the optimum amount of coal prouced by the most hydropower line to make holes is 150kg/m.(2)Using COMSOL software to simulate and analyze the influence of different drilling distances on the formation of coal seam line.The results show that with the increase of the spacing of the drilling holes in the line,the residual gas pressure peak of the coal seam between the holes in the line after the gas extraction is gradually increased.When the hole spacing is 4.8m,the gas pressure is 0.45MPa;when the hole spacing is 6.4m,the gas pressure of the coal between the holes is about 0.65MPa;combined with the "double 6" gas control standard of Henan Province,the line forming gas after the extraction,the pressure is reduced to 0.6 MPa as a safety standard.When the reasonable spacing of the hole in the hole drilling is determined to be 4.8 m,the purpose of the coal seam pressure relief can be achieved.(3)It is determined by theoretical calculation that the maximum water pressure of the bedding line forming hole is 3.8 MPa.The field test of the acupoint technology of the Xuehu coal mine hydraulic line was carried out.The stress monitoring sensor was used to investigate the stress evolution law of the coal body after the acupoint formation.The effective influence range of the single hole line acupoint was between2.4m and 3.2m.When the double hole line acupoint test is carried out,when the hole spacing of the line forming hole is 4.8m,the drilling stress decreases by 29%compared with the single hole line forming hole at 2.4m,and the double hole line acupoint stress decreases by as much as 46%.The pressure relief zones are covered by each other,and the coal body is fully relieved,effectively avoiding the occurrence of gas drainage blind spots.(4)The gas drainage concentration,coal seam residual gas content and gas pressure of the wire-forming hole were measured and analyzed,the pressure-relieving effect of the hydraulic line acupointing measures was investigated.The results show that the concentration of gas-drilling holes in the line is significantly higher than that in ordinary boreholes,and the average gas drainage concentration is increased by 4.3times.The highest residual gas content and pressure in the effective pressure-relieving area of the line-forming holes are 5.4m3/t,0.31 MPa,both fell below the critical value,and the residual gas content of the double-hole line forming hole with the hole spacing of 4.8m is only 4.8m3/t,which is much lower than the gas control standard of Henan Province.The effect of the coal seam pressure relief is obvious.The research results reveal the stress and gas distribution law around the borehole of the bedding hydraulic line,determine the best technical parameters and effective influence range of the Xuehu coal mine hydraulic line,and improve the gas drainage effect and anti-burst efficiency of Xuehu Coal Mine.It has reference significance for gas control and outburst prevention work of high adsorption and low permeability outburst coal seams. |
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