Abstract:  In order to measure effective drainage radius exactly, we propose the method based on gas flow and pressure of boreholes. Under the index of remnant gas pressure less than 0.74 MPa and pre-drainage rate more than 30%, the computing formula is deduced based on the negative exponent attenuation law of gas flow, and the effective drainage radius is determined in combination with the variation of gas pressure. The method is applied in the arrangement of zonal pre-drainage boreholes. The effective drainage radius of different pre-drainage time and the utmost pre-drainage time are analyzed. Based on the premise that effective drainage radius reaches to 2.5 m in 90 pre-drainage days, the boreholes are designed to eliminate coal and gas outburst. The measurement method is demonstrated valid in outburst elimination by the examination of remnant gas pressure,pre-drainage rate and the zonal verification during the coal roadway driving.

Key words: effective drainage radius；gas flow, gas pressure；outburst elimination；zonal pre-drainage