Measurement of stress-relief zone width of roadway by borehole gas continuous flow method

Abstract

In order to accurately measure the width of stress ̄relief zone ahead of roadway working faceꎬ borehole gas continuous flow method was proposed based on the relationship between gas flow discharged from coals and in ̄suit stressꎬ and its feasibility was verified theoretically. Thenꎬ borehole gas flow was measured in 2303 ventilating roadway of Xuehu coal mine by using outburst prediction device. The results show that gas flow increases first and then decreases with its peak being the boundary of stress ̄relief zoneꎬ and the width of the zone ahead of working face is determined to be 9 10 meter. Meanwhileꎬ that measured by using drillings amount and drillings gas absorption index Δh2 is 9􀆰 5-10 meterꎬ consistent with results of borehole gas continuous flow methodꎬ therefore verifying its reliability in determining width of stress ̄relief zone.