The II3123 face is a light type caving face of three-soft coal seam. the roof is cracked, sloughing and roof fall often occur.
前言： 石台煤矿II3123工作面为“三软”煤层轻放工作面，顶板破碎易掉，片帮、冒顶时常发生。
The principle of increasing gas emission rate by long hole blasting in the crossing hole is discussed. The radius cracked zone in coal seam caused by long hole blasting is calculated.
简要论述了深孔爆破提高瓦斯抽放的机理，以煤体中柱状装药爆炸后的裂隙圈半径进行了计算。
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