Effective gas drainage of high flow and purity should be obtained in the "O" ring and stress relief zone.
Stress relief in protected No. 13 seam occurred between stress relief lines due to lower strata subsidence, thus "stress relief and permeability enhancement" effect appeared in stress relief zone, resulted in significant increase in the permeability of rock and coal seam in this zone.
The combined new technique can improve the effective effected range of pressure relief zone around a single drilling-hole, which can reduce coal and gas outburst by combining "point", "line", "surface", and "body" of the front of working face coal mass.
The area around the convention center morphs into what looks like a makeshift disaster relief zone, but I suppose that's also the ideal scenario for sci-fi/fantasy fans, because it's like you're living inside the movie World War Z. .
They can also rely on inertial navigation data and compass direction to support beacon use during limited satellite reception (Woodman, 2007), for instance in urban canyons, unmapped subterranean areas, contested environments, and disaster-relief zones.
As the strata elevation increases, the stress-relief zones become smaller, decreasing in size to 93 m and 65 m in the strata of line III and B4 coal seam (lines I II), respectively.
(3) The widths of the stress-relief zones in B4 coal seam in the numerical simulation differed from those in the similar material simulation, but the stress-relief coefficient was symmetrical along the dip.
Pressure-relief zone is mainly concentrated in the side of outlet roadway.
Based on the stress-relief zone theory, we establish the stability condition of stress-relief zone in a coal mine laneway and find out the relationship between the stress-relief zone and the coal and gas outburst risk and analyze the function of stress-relief zone in preventing coal and gas outburst.
