近距离煤层群开采底板不同分区采动裂隙动态演化规律

为了研究采动影响下底板不同应力分区裂隙动态分布及其演化规律，运用弹塑性力学和卸荷条件下断裂力学等相关力学理论分析了不同分区裂隙张开、扩展力学机理，提出不同分区裂纹扩展的应力、位移条件，通过FLAC3D和UDEC数值模拟软件分别研究了底板三维应力状态、位移变化和裂隙演化规律，对底板应力分区做出量化，同时得到采动影响下底板裂隙发育“O”形圈及其动态变化。通对底板不同分区内裂隙的发育倾角统计结果分析，得到了底板不同分区裂隙发育特点：压缩区裂隙多为弯折拉伸裂纹，方位角大致为垂直方向；过渡区裂纹多为反向滑移和弯折扩展裂纹，裂纹倾角多为45°以上；膨胀区多为Ⅱ型剪切裂纹，倾角大部分在45°以下；裂隙发育特征与力学分析相吻合。

Dynamic evolution rules of mining-induced fractures in different floor area of short-distance coal seams

In order to study the dynamic distribution and evolution law of floor fracture in different stress partition influenced by mining,authors analyzed the mechanic mechanism of fracture’s open and extension in different stress partitions by the elastic-plastic mechanics and the unloading fracture mechanics theory,then proposed the conditions of stress and displacement of crack propagation in different partitions.The 3D dimensional stress state,displacement changes,the crack evolution law of mining floor were monitored by numerical simulation software of FLAC3D and UDEC,and also,the floor stress partition was quantized,the bottom fracture “O” ring and it’s dynamic change under the influence of mining was obtained at the same time.Fracture characteristics in different partitions were obtained by analyzing the statistical result of crack growth angles in different floor partitions：cracks were bending-tensile cracks in compression zone,azimuth angles were roughly perpendicular direction;cracks were more reverse slip and bending-extension cracks in transition zone,and most of their angles were above 45°;and cracks were mostly TypeⅡ in expansion area,their angles were mostly blow 45°.Fracture characteristics were in conformity with the mechanics analysis.