| Underground mining is a large part in China, the crustal stress and gas pressure are becoming more and more severe along with increasing depth. Aiming to the feature of low gas permeability in soft coal bed, such as serious degree of damage, soft and so on, the effectiveness of gas extraction is not optimal by traditional method, which has been in trouble with prevention of coal and gas outburst. Increasing gas permeability and improving the effectiveness of gas extraction are the best way to prevent coal and gas outburst and improve the safety and high efficiency by hydraulic punching.In this paper, on the basis of analyzing dynamic characteristics of hydraulic punching process and factors affecting coal water jet break, respectively analyzing the coal water jet erosion dynamic process by using ANSYS/LS-DYNA numerical simulation software, and analyzing and calculating the change impacts of hydraulic punching holes around the coal on the stress and strain. The test of hydraulic flushing technology is conducted in No.728working face top slate lane in Qingdong Coal, the average amount of coal hole punch is1.3t, the front and rear hydraulic flushing hole diameter expanded to593.4millimetre, is increased by6.3times. The rear hydraulic flushing hole gas extraction concentration and pure quantity are investigated, the maximum of the gas extraction concentration in every single bore is increased by6.5times, up to6.53%, and the most gas quantity is0.4m3/min, is more than front hydraulic flushing by0.33m3/min, is increased by5.7times. The most residual gas pressure is0.21MPa, and the most residual gas amount is3.17m3/t, which proves the effectiveness of pressure relief and antireflection.In the process of coal roadway excavation, combined with Smax is3.9kg, k1is0.11mL/gminl/2,⊿h2is80Pa, Δp is8mmHg,f is above o.7.It turns out that the effectiveness of hydraulic flushing technology is very good.The hydraulic flushing technology not only saves time but also cost in No.728working face. |
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