Study on gas drainage radius and distance between boreholesbased on dynamic fluid-solid coupling model

In order to set up the gas drainage radius and the layout distance between boreholes, based on the overburden strata pressure, geostress and seam gas pressure distribution condition and to consider the coal dilatancy affected to the coal pore ratio and the permeability dynamic variation equation, a seepage dynamic fluid-solid coupling model of the borehole gas drainage was established. Based on the seepage fluid-solid coupling model obtained, the model was embedded in the Comsol Multiphysics for the simulation calculation and No. 11528 coal mining face was applied to the site approval on the single borehole and multi borehole gas drainage experiments. The study results showed that the gas pressure variation in the gas drainage borehole along the straight line distribution mainly would be reduced along the straight line and along the delta top layout, the borehole gas pressure reduction range would be a full semicircle. The single borehole gas drainage radius was 2.05 m and a layout distance of the single borehole gas drainage and the multi boreholes layout along the straight line was 1.8 times longer than the single borehole gas drainage radius. The layout distance of the multi boreholes at the delta top points would be 1.6 times longer than the single borehole gas drainage radius.