在新安煤田新建的三对矿井，主采煤层均为山西组2-1三软不稳定煤层。
There are three coal mines in Xin'an Coalfield. The Shanxi group irregular(2-1) coal seam has soft roof, soft coal and soft floor.
前言： 通过对“三软”不稳定煤层采煤工作面瓦斯来源的分析，介绍了采用顶板岩石钻孔抽放解决瓦斯问题的原理和方法。
Based on the analysis of gas source at the working face with "three-soft" unsteady coal seam, the authors introduce the principle and method of gas suction by roof-rock drilling.
着重探讨了煤层并壁不稳定机理，结果表明，煤层井壁不稳定是物理、化学、力学与机械等因素的综合效应。
The result shows that coal seam wellbore unstability is a synthetic effect caused by such factors as physics, chemistry, mechanics and machinery.
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