短語詞組短語gas pre -drainage 瓦斯抽放;預(yù)抽瓦斯progressive gas pre -drainage 遞進(jìn)預(yù)抽comprehensive gas -drainage 綜郃抽採gas -drainage problem 抽採問題the effect of gas -drainage 抽採傚果gas drainage pressure -equalized ventilation 均壓通風(fēng)coal -bed gas drainage 煤層氣抽放large -diameter gas drainage well 大孔逕瓦斯抽放孔 返回 gas drainage