Study on Numerical Simulation of Coal Stress and Strain Around Blowout Borehole Drilled Through Strata

According to the mechanism of the coal and gas outburst, based on a full analysis on the cause of the blowout borehole drilling through the low permeab ility seam and the coal moving deformation, a FLAC3Dand a related theory was applied to the numerical simulation study on the stress field distribution law, the displac ement filed distribution law and others of the coal and rock around the blowout borehole. The study showed that when the blowout borehole formed, in the coal around t he blowout borehole, there would be a pressure released zone, fracturing zone and elastic stress zone. The cracks would be produced, expended and connected within coal. The radial displacement forward to the borehole center occurred in the coal around the borehole, the displacement size and the distance of the displacement to th e blowout borehole, creep coal would be related to the blocking and pressure releasing of the coal rheology deformation in the later sequence. The influence scope of t he blowout borehole would be a positive correlation to the radius of the blowout borehole, the depth of the seam buried and the thickness of the seam. The pressure rel easing quantity would be a positive correlation to the radius of the blowout borehole and a negative correlation to the depth of the seam buried.