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Abstract In order to solve the problem of borehole collapse caused by the use of hydraulic punching and cavitation technology in deep soft coal seam, which makes the sieve tube unable to be lowered to the specified position and the efficiency of the sealing stage, this paper proposes an integrated technology of drilling, punching and protecting, which relies on a special water knife to realize the integration of drilling, hydraulic punching and cavitation and the lowering of the hole protecting sieve tube without lifting the drill. Taking the 31051 working face of Lugou Mine as the experimental area, a comparative experiment of traditional hydraulic punching and drilling-punching-protection integration was set up. According to the experimental data, the time of drilling, punching and protecting integrated hole sealing is 50.8 % shorter than that of ordinary hydraulic punching and cavitation technology, and the success rate is 98 %. After 45 days of extraction, the average concentration of gas is stable at about 66 %, and the attenuation range is only 7 %. The average gas purity is 0.293 m3/min, which is 1.6 times that of ordinary hydraulic punching. The attenuation coefficient is 0.017, which is 29.5 % lower than that of ordinary hydraulic punching. The results show that the integrated hydraulic punching technology of drilling, punching and protecting can effectively improve the efficiency of gas extraction in soft coal seam and provide technical support for gas control in deep coal seam.
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