The Method of Determining Layer in Bottom Drainage Roadway Taking Account of the Influence of Drilling Angle on Gas Extraction Effect

The pre-drainage of coalbed methane through boreholes in the bottom drainage roadway (BDR) is key measure to prevent and control coal gas outburst. Different arrangement layers BDR will make a difference range drilling angle affect extraction effect. In this paper, mathematical model rock loose circle area around elliptical was constructed. Meanwhile, fluid–solid coupling constructed by using COMSOL software, dynamic response permeability volumetric strain with pressure Klinkenberg effect are considered, change on relief seam studied. results showed that distance between layer would decrease, effective length at same point increases. decayed negatively exponentially increase angle. As decreased, stress major axis ellipse cross-section increased, so prone collapse, hindered. Finally, an optimal method determining under multiple factors established combining measured ground stress. Through field measurement, rate optimized scheme 60% higher than original scheme.