Study on pressure released scope of hydraulic flushing and gas drainage law

In order to study the pressure released and permeability improved action mechanism of the coal around with the borehole by the hydraulic flushing, with the gas pressure observation method and the drainage parameter monitoring as the technical means, the underground mine investigation test and data analysis method were applied to study the pressure released features of the coal around the hydraulic flushing borehole and the gas drainage |aw. The results showed that in Zhongma Village Mine, the pressure released influence scope of the coal around the hydraulic flushing borehole was 5 m and the full pressure released scope was 1.5 m. The ga s drainage law of the hydraulic flushing borehole could be divided into two stages. The first stage would be a gas high efficient drainage period ( 5 days before the gas drainage operation) . At this stage, the sources of the gas drainage volume were mainly the rapid desorption and released coal gas from the fully pressure released zon e with large amount of desorption and fast decay and the attenuation of the gas drainage rate in the hydraulic flushing borehole would be in a power function linear law. The second stage would be a gas stable drainage period ( 5 days after the gas drainage) . At this stage, the coal gas desorption from the full pressure released zone W ould be completed, the sources of the gas drainage would be the coal gas desorption migration from the pressure released influence zone mainly and the attenuation of the gas drainage rate would be stable and in index function features.