三软煤层首采工作面局部冒顶原因及控制研究

Study on reasons and control of partial roof caving in the first mining face of three-soft coal seam

为解决三软煤层工作面易发生冒顶事故的问题,采用X射线衍射分析、围岩电镜扫描和现场实测的方法研究了三软煤层巷道局部冒顶的影响因素,并开展了现场局部冒顶控制实践。结果表明:围岩中粘土矿物含量较高,占矿物总含量的50%~66%,并具有吸水软化膨胀的力学特性,降低了岩体力学强度,中砂岩微裂隙、微孔隙较为发育、贯通性好、裂缝宽,泥岩中大量可见裂隙和微溶孔,致使其稳定性较整块结构岩体差;综采工作面巷道局部冒顶的主要原因是冒顶区巷道高度大、顶板较为破碎,支护不及时、淋水影响。控制实践表明:通过改善支架工况、带压移架,保证支架初撑力足够大,能够预先控制顶板,有利于防止直接顶离层、控制局部冒顶。

In order to solve the roof caving accident in three-soft coal seam, the influencing factors of partial roof caving in three-soft coal seam were studied by X-ray diffraction analysis, scanning electron microscopy and field measurement. And roof caving control practice was carried out. The results show that, clay mineral content in the surrounding rock is high, accounting for 50% ~ 66% of the total mineral, and has the mechanical properties softening and expansion after water absorption, which reduces the mechanical strength of the rock ; microfissure and micropores of medium sandstone are developed, which leads to good connectivity and wide fissures; a large number of fissures and micro dissolution pore can be seen in the mudstone, leading to poor stability. Main reason of the partial roof caving is： large roadway height in roof caving area, roof breaking, late supporting and water influence. Control practice shows that through improving the support conditions, support sliding with pressure, the support setting load is sufficient to control the roof in advance, which is conducive to prevent immediate roof separation, and control the partial roof caving.