采用理论分析、数值模拟和现场实测综合研究方法,系统阐明了深部采场底板围岩三维应力场的空间分布特征和时间变化规律,揭示了深部采场底板围岩在多力学参量作用下的裂隙演化力学机制.研究表明,底板岩层卸压扰动应力场的重分布具有选择性,底板岩层3个方向的应力并非完全卸压,部分区域甚至存在水平应力集中.采场底板围岩中最大主应力的集中与方向的偏转,引起最大主偏应力大小和形态的变化,进而引起采场底板围岩原始裂纹的起裂与扩展.依据采场底板围岩最大主偏应力场的差异性,将煤层底板岩层划分为未受采动影响区、过渡区、最大主偏应力集中区和卸压膨胀区4个区域.与实测资料对比表明,充分采动前,采场底板围岩中最大主应力集中区以上,岩体由整体连续渐变为宏观断裂将经历3个阶段,分别为超前支承压力作用下的预先随机微破裂、最大主偏应力集中引起的裂纹稳定扩展、裂纹间突变协同效应引起的宏观拉伸破坏.研究成果为深部采场底板危险区块快速判定与主动调控提供了理论基础.
Thespatial distribution characteristics and changes with time for three dimensional ground stress field of coal floor are illuminated by usingtheoretical analysis and numerical simulations. Me-chanical mechanism of dynamic fracture evolution under the multiple mechanics parameters of coal floor in deep mining is revealed. According to the analysis results, the redistribution of 3D stress field is got. Because of the major principal stress concentration and direction deflection, the size and shape of the major principal deviator stress could change. That cause the microfractures initiate and propagate. The zone in the coal floor is divided into four areas, unaffected area, interfacial transition area, major-principal stress concentration area, pressure drop and expansion area according to the variability of ma-jor principal stress. Compared with measured data, the change of going from fractured rock mass inte-gral continuity to macroscopic fracture above the major principal stress concentration areas has three phases, which are the random microcracks for the advanced abutment pressure, stable growth of micro cracks for the concentration of the major principal deviator stress and macroscopic failure for mutational collaboration of numerous tiny cracks. The research results provide a theoretical basis for the rapid de-termination and active control of the dangerous area of coal floor in deep mining.