Stability Analysis of Sealing Section in Gas Extraction Hole Based on Strain Softening Model

For solving the problem that serious gas leakage from the drainage hole, based on the strain-softening model whose cohesion reduces along the plastic area, the stability of the rock around the sealing section was researched. The methods of theoretical deduction and numerical simulation were adopted for the research. Research shows that the plastic area and displacement gets a significant increase in the rock around the hole. With the raise of the pressure in the hole, the plastic area of the wall rock and the displacement of the hole wall are reduced; the borehole tends to be more steady. Research findings were applied to sealing practices of gas extraction in a coal mine in Henan province; it shows that in the soft coal seam, the gas concentrate can improve more than 18.1% with pocket assay grouting sealing method rather than polyurethane sealing method.