Gas Drainage of undischarged pressure hole at original coal seam is an indispensable link in coal mine production.The result of releasing gas depends on natural ventilated coefficient.

• 本煤层未卸压钻孔抽放,是煤矿生产系统中不可缺少的环节,由于煤层的天然透气系数不同,抽排瓦斯的效果也不同。