| As a complicated mine phenomenon, coal and rock outburst is featured by high risk and frequency, especially when opens up coal seam in the crosscut. The research figure shows that the 75.9% of the coal and rock outburst occurs in the crosscut among dozens of extremely outburst in China. For the phenomenon, scholars in the world proposed several ways, take deep hole presplitting blast, hydraulic fracturing and acidification treatment for example, however, their construction technologies are too complicated, the period of the crosscut and preparing laneway are too long, which restricts the efficiency of the mine. Therefore, it is necessary that develop the technology of high pressure pulsed water jet(HPWJ) to slot the coal seam, which has significant meaning in engineering and economy.Supported by Innovation Groups Fund Project"Theory of rock cracking by High-pressure water jet and its basic application research in underground engineering (ID: 50621403)"of National Natural Science Foundation, the author proposes a new way that using the HPWJ to slot the coal seam. Based on the study of the dynamic function of the coal seam impelled by HPWJ, the evolution characters of the crakes and change law of the coal seam permeability is analyzed. What's more, based on the theory of the nonlinear gas seepage and geophysical field effect gas flow, how the HPWJ affects the law of the gas seepage is shown. Besides, the device of the slotting system with HPWJ and its construction technologies is studied, and its slotting parameter is calculated depending on the theory of fluid mechanics and seepage mechanics. Finally, the system is applied in the coal mine. The main conclusions are as follows:①The stress field around borehole would be change, because of the slotting in the coal seam with the HPWJ, and then the change would from stress released area which is enlarged by oscillation of the HPWJ and would increase the permeability of the coal seam. The pulse with different frequency would form fracture with different size, and then the fracture would experience four stages, which are original failure, developing of the fracture, run-through each other and developing further. The fracture provides the channel of the gas flow, which is a base of the high drainage gas.②Besides, the impelled dynamic function of the HPWJ is calculated, the gas seepage function in the coal seam slotted by the HPWJ is gained basing on the seepage theory.③The slotting system device of HPWJ is developed. Moreover, the force of the HPWJ on the unit coal and the relation between coal particle and water velocity are also calculated. And then, the pressure and flow are shown, which is critical important for the system and its slotting process and is the base of the application the system in the coal mine.④The slotting system is applied successfully on the crosscut in Songzao, and the data shows that the maximum K1 in the K1 seam of the crosscut +175N2#, slotted by HPWJ, is 0.85 mL/g·min1/2 in 3 days. However the maximum K1 in the crosscut +175, which is slotted by HPWJ, changes slightly. In crosscut +175N2#, the gas concentration and the gas flow per per-borehole of the slotted borehole are 36.8 times and 10times at least as large as the other boreholes respectively. What's more the gas drainage rate, gas drainage quantity and the gas drainage area in crosscut +175N2# are 3.2 times, 1.85 times and 2.03 times as large as crosscut +175 respectively. In addition, the gas pre-drainage tiem and cutting through time are shorten 54.75% and 44.8% respectively, the borehole quantity and borehole scale decrease 53.2% and 33.7% respectively. Moreover, the maximum of the K1 decrease by 44.9%, and the K1 seam turns to easy drainage from hard drainage. |
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