上述方法存在的问题是钻孔法有效抽采孔段长度短、终孔孔径小、抽采效果差，巷道法施工工期长、费用昂贵、不利于瓦斯利用。
The effect of gas discharging is limited by length , diameter of borehole in coal seam and high cost of laneway development.
上述方法存在的问题是钻孔法有效抽采孔段长度短、终孔孔径小、抽采效果差，巷道法施工工期长、费用昂贵、不利于瓦斯利用。
The effect of gas discharging is limited by length , diameter of borehole in coal seam and high cost of laneway development.
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