Negative-pressure extraction is one of the most important factors affecting the seepage law of coal gas in the perforated hole. To study its influence

the gas flow in the hole was determined by designing a similar simulation test platform for gas seepage. Moreover

the numerical software was used to analyze the gas seepage in the coal around the hole. Combined with the above conclusions

the percolation characteristics of gas in the coal around the hole was studied. The results showed that the negative pressure was used to provide the power for gas seeping from the coal to the borehole. When the negative pressure was set in the range of 25~35 kPa

the Reynolds number was concentrated between 10 and 20. Thus

the low-speed turbulent flow is ensured

which was conducive to extracting the gas efficiently. With the increase of pumping time

the effect of negative pressure on the gas extraction gradually became weak

and the gas flow showed a negative exponential decay with time. The saturated value of coal seepage velocity was between 7.41×10?6 m/s and 1.30×10?5 m/s. The internal viscous resistance of the coal body inhibited the gas seepage. With increasing the negative-pressure extraction

the negative pressure of the borehole increased faster than that in the coal around the hole

which indicated the effect of the negative pressure on the borehole was more significant.