Analysis on attenuation feature of gas flow in borehole passed through beds in high gassy mine

In order to study a single hole gas limit drainage volume and the flow attenuation characteristics of the borehole passed through beds in the high gassy mine, a gas flow rate and gas concentration detection device in the seam borehole self developed was applied to the measurement on the single hole gas flow and concentration in the borehole passed through beds of the floor gas drainage gateway. The attenuation variation law curves of the single hole gas flow and concentration were drawn. Under the condition of the high negative pressure drainage, based on the single hole gas flow attenuation theory, high seepage mechanics, elastic-plastic mechanics and other related theory, a comprehensive analysis was conducted on the variation and attenuation law of the borehole gas flow. The result showed that:①the borehole gas flow attenuation would have three stages with the time passed, including the linear attenuation stage, unstable fluctuation and stable and gentle attenuation stage. ②When the borehole gas flow attenuation coefficient was measured, the borehole gas flow attenuation was just in a relative stable attenuation stage and the measuring period would be 50 days. ③Based on the relative relationship between the stress around the borehole and the gas drainage flow, the gas drainage flow and time as determined would be in a negative index relational expression.