Abstract: In this paper, to accurately determine the drainage radius, and reasonably estimate the drainage parameters of different regions in the same mine, the mathematical model of gas pressure in coalmass around borehole was established by the gas flow theories, the calculation program of drainage radius was designed by using VB.NET, and the distribution rules of gas pressure around borehole and the influence factors were simulated. Meanwhile, drainage radius was measured with the method of pressure-drop testing by circumference setting-borehole. The results show that the draining time, permeabilities and subpressure are the main factors which influencing the distribution rules of gas pressure. The actual measured drainage radius of No.8 Coal Seam in Luling Mine is 4.32 m, while the calculation results is 4.43 m, which means the proportional coefficient method can calculate the drainage radius of other zones in the mine reasonably. The achievements in this paper can provide basis for gas drainage borehole design, raise gas drainage efficiency, and ensure safety mining.

Key words: drainage radius, mathematical model, gas pressure, circular hole arrangement