Optimized design and application of three dimensional gas drainage boreholes in driving face

in order to improve the gas drainage quantity before the driving operation of the high gassy gateway driving face and to reduce the gas pre-warming times during the driving process.according to the plan mode drainage boreholes in the high gassy gatew ay drving face in Yuwu Mine could notflly cover the ful s am thickness and the gas drainage quantty was low,with adjustnent of the borehole distrbution mode and the borehole opening angletheoptinmized design was conducted on he released boreholes of the driving face and the sidew al protecton boreholes inthe two sidewl iling site and the gas drainage boreholes o thedrvingfae ware :hanged from the plan mode drainage to a three dimensional drainage.The site experiment showed that thegas drainage voune fraction with tree dimerso al drainage boreholes was improved by 11%,the gas drainage pure fow was improved by 0.14 ni3l min and the gas volume fracion of the air retuning fiow was reduced fom 0.3% to 0.4%.Therefore.the piot pressure released of thefill thck sean could not only reduce the outburt dangerbut coul in advance cut of and release the gas in he seam.;could highly reduce the gas emission volume of the driving face and could ensure thegas emission evenly during the driving proc.ss whilethegateway dring.