深井超长工作面基本顶分区破断模型与支架阻力分布特征

Roof sub-regional fracturing and support resistance distribution in deep longwall face with ultra-large length

开采深度和工作面长度增加导致采场矿压显现程度和空间分布特征发生改变,增加了该类采场围岩失稳类型的不确定性及控制难度。针对深井超长工作面异常矿压现象发生频率高、预测难度大等问题,采用理论分析、室内实验和实测等方法分析了该类采场基本顶破断类型和支架阻力分布特征。结果表明:开采深度增加提高了岩体中裂隙发育程度,裂隙尺寸服从对数正态分布,裂隙倾角和倾向服从正态分布;基于蒙特-卡罗模拟方法实现深井超长工作面基本顶三维重构,工作面长度增加导致基本顶中部存在裂隙的概率升高,增大了基本顶在工作面中部发生局部破断的可能性;建立深井超长工作面基本顶分区破断力学模型,采用上限定理推导出完整基本顶的整体承载能力以及基本顶中存在1条和2条原生裂隙时的局部承载能力,获得基本顶在裂隙影响区发生局部分区破断和迁移现象的力学判据;基本顶分区破断现象导致破断岩块在空间上呈非均匀分布,表现为工作面中部块度小、两端块度大的特征;分区破断模型预测结果同相似模拟实验结果吻合,解释了深井超长工作面开采实践中发现的顶板压力沿工作面方向的非均匀分布现象。

increase in the cover depth and length of longwall face leads to some drastic changes in mine pressure occurrence and spatial distribution.Such changes result in a great challenge in surrounding rock control.In order to realize an effective control of the abnormal mine pressure occurrences,happening frequently and difficult to be predicted in deep longwall face with ultra-large length, the roof rupture characteristics and support resistance distribution in such a longwall face are investigated.Pre-existing fracture development significantly increases due to the increase of cover depth.The fracture size and orientations obey lognormal and normal distributions, respectively.The main roof with randomly distributed fractures is reconstructed based on such statistical distributions and DFN method.The large length of longwall face increases the probability of the existence of fractures in exposed main roof.Sub-regional rupture model is established for the main roof with one and two fractures,whose limit load-bearing capacities are achieved.The mechanical condition for the occurrence of the sub-regional rupture of main roof and its subsequent migration is achieved using upper bound theory.Spatial distribution of the broken blocks after the main roof fracturing is non-uniform.The block volume in the middle section of the longwall face is small while that of the blocks on two sides of the longwall face is relatively large.Such distribution reasonably explains the non-uniform distribution of the support resistance along the dip direction of the longwall face.The theoretical conclusions are in good accordance with the experimental results and field measurement.