Gas Evolution Principle during Gas Drainage from a Drill Hole along the Coal Seam and Reasonable Borehole Layout Spacing.

The three curves ( Figure 6 b) all show a decreasing trend, which represents that the difference of the gas migration velocity between the two nodes gradually decreases with the increase of the gas drainage time, which can also partly confirm that in the late stage of gas drainage, with the gas pressure relief of the coal seam, the fissure structure of the coal body pore becomes more and more stable. 3.4.

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