| Hydraulic punching technology is currently recognized as the best method to increase permeability of coal seam.Its main function is to cause pressure relief of coal body,make cracks develop and connect in coal body,reduce gas flow resistance and improve gas drainage effect.At the same time,the water jet will wet the coal,and the increase of water content in the coal will promote the desorption of gas in the coal.At the same time,the high-pressure water jet into the coal increases the water content in the coal and promotes the desorption of gas in the coal.Hydraulic punching is widely used in regional permeability enhancement,such as cross cut coal uncovering and through layer drilling.However,for the bedding hole in the mining face area,due to the long coal hole section of the extraction hole,it is easy to cause a large area of hole collapse after punching,resulting in poor slag discharge and other reasons,and it is difficult to adopt hydraulic punching technology for bedding hole permeability enhancement,which leads to the hydraulic punching in bedding hole There are few researches on the technology of hole permeability enhancement.In this paper,aiming at the problems of long coal washing section and serious hole collapse after punching due to the creep characteristics of coal,combined with the problems of low permeability of coal seam,rapid attenuation of gas concentration and poor drainage effect of gas drainage boreholes in the coal seam in baiyangling coal mine of China Coal Xiyang energy Co.,Ltd.,the high-pressure water jet drilling along the seam is proposed to carry out the research Study on the synergistic effect of hydraulic punching technology in bedding hole on gas drainage.This paper first introduces the research status of high-pressure water jet hydraulic punching technology at home and abroad,and analyzes the penetration mechanism of hydraulic punching on coal seam.COMSOL Multiphysics simulation software was used to simulate the effective radius of hole making under different factors,and the field test of effective radius of hole making by hydraulic punching was carried out.Finally,through the field test of hole punching in 15108 jiaoshun of baiyangling coal mine,the effect of hole punching and penetration enhancement was investigated.The effective influence radius of hydraulic punching hole increases with the increase of the radius,but the increasing range becomes slow.The numerical simulation results show that the maximum effective radius of hydraulic punching is 3.10m.The results show that the radius of cavity making is 0.4m.The key of hole drilling technology is coal breaking water pressure,which is mainly composed of the effective coal breaking water pressure at the outlet of water knife and the water pressure loss along the way when high-pressure water is transported by high-pressure hose.The effective coal breaking water pressure is directly related to the firmness coefficient of coal.The results show that the firmness coefficient of 15108working face in baiyangling coal mine is 1.22.According to the empirical formula,the effective coal breaking water pressure should be 14.64MPa-24.40MPa.According to the field test conditions,it is calculated that the water pressure loss along the way is 0.60MPa,The leakage water pressure is 1.52MPa-2.50MPa,the water pressure of the water pump for hole making in baiyangling coal mine is 16.76MPa-27.50MPa.The results show that the maximum gas concentration of the hole making boreholes is 43.00%,and the average gas concentration of the three groups of hole making boreholes is 13.93%,5.69%and 7.05%every day in one month.Compared with the ordinary boreholes,the maximum gas concentration of the hole making boreholes is increased by5.80 times,with an average increase of 3.70%Times.The average gas extraction pure amount of ordinary drilling hole is 0.003m ~3/min in a month,the maximum gas extraction gas of hole making drilling can reach 0.040 m~3/min,and the average gas extraction gas pure amount in one month is 0.012m m~3/min.compared with ordinary drilling,it is 4times higher.The average attenuation coefficient of gas flow in hole making borehole and common borehole is 0.10 and 0.13 respectively within one month of drainage.Compared with ordinary drilling,the attenuation coefficient of drilling hole can be reduced by 0.23times.According to the field drilling hole construction situation,it is concluded that the forward drilling hole construction has the advantages of easy slag removal,high drilling hole forming rate,and difficult to hold the drill during drilling construction.it is concluded that the best coal yield of drilling hole construction should be controlled at about 0.7t/m.There are 60 pictures,17 tables and 61 references. |
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