Abstract: To determine the reasonable distance of gas drainage boreholes in coal seam being mined, based on the control equations of seepage and deformation fields, and the coupling equations of porosity and permeability, the solid and gas coupling mathematical model of gas seepage in drilling extraction was established. The drainage radius of gas extraction borehole in current coal seam was calculated by numerical simulation, and the relation between the borehole distance and extraction radius of single-borehole was deduced. Taking coalface 15107 of Huangyanhui coal mine for example, by the gas drainage experiments of single drilling and multiple drillings in this face, the correctness of the drainage radius, and the relation between borehole distance and extraction radius were calculated and verified. The research results provide a scientific basis for gas extraction.

Key words: borehole, drilling distance, extraction radius, gas pressure, numerical simulation