基于动载效应的特厚煤层综放采场支架围岩相互作用机理

Ultra-thick coal seam mining results in large space stope, wide failure range in overburden strata and complicated interactions of support and surrounding rock. Therefore, dynamic loading effect and its influence on the interactions of support and surrounding rock are studied in the program. Three-dimensional dynamic and static load coupling testing system is used to simulate the static abutment pressure, the strong pressure from far field and the disturbance from mining face. The influence of the actions of different dynamic strength and frequency on the mechanical properties of coal and rock mass and its fracture surface are analyzed. The failure mechanism of coal and rock mass in large space stope is explored. Large-scale physical modeling, discrete element numerical modeling, and field measurements are employed to investigate the evolution process of roof strata; illuminate the dynamic effect in stope; establish the structural mechanics model of “caved roof strata-near field roof strata-support-coal wall” near the coal face; analysis the stability of coal wall and the compressive deformation of caved roof strata influenced by the change of support resistance; reveal the interactions between the structural evolution of near field roof strata and the synergistic actions of caved roof strata, coal wall and support. Put forward effective regulatory mechanism of the interactions of support and surrounding rock mass for the typical conditions. The results of this study serve to provide theoretical support and scientific basis for the Intelligent warning and active control of strong mining pressure in mining the extra-thick coal seam.

特厚煤层开采空间大，覆岩破坏范围广，动载效应显著，支架与围岩相互作用关系复杂。为此，本项目拟对特厚煤层综放采场动载效应及其影响下的支架围岩相互作用关系进行研究。利用煤岩体三维动静载耦合试验系统，模拟大空间采场静态支承压力、远场强矿压冲击和工作面开采扰动作用，分析动载强度和频率变化对煤岩体及其破裂面力学特性的影响，探明大空间采场煤岩体破裂失稳机理；综合大尺度物理模拟、离散元数值模拟、现场实测像等技术方法，研究近场覆岩结构演化规律，阐明采场动载效应。构建工作面区域“采空区垮落岩体-近场覆岩-液压支架-煤壁”结构体力学模型，分析支架工作阻力变化对煤壁稳定性和垮落岩体压实度的影响规律，揭示采场覆岩结构演化与垮落岩体、煤壁和液压支架协同作用的相互影响机理；针对具体工况，建立支架与围相互作用的有效调控机制。研究成果可为特厚煤层开采大空间采场强矿压智能预警与主动防控提供理论支持和科学依据。

大采高综放开采技术日渐成熟并在我国特厚煤层的开采中获得广泛应用。然而，特厚煤层开采空间大，覆岩破坏范围广，动载效应显著，支架与围岩相互作用关系复杂。为此，本项目对特厚煤层综放采场动载效应及其影响下的支架围岩相互作用关系开展了研究。具体包括三个方面的内容：（1）动静载耦合作用对煤岩体力学特性的影响；（2）近场覆岩结构特征及其演化规律；（3）覆岩结构演化与垮落岩体、煤壁和液压支架协同作用的相互影响。针对研究内容一，研发了三维动静载耦合压力试验机，开展了中低应变率动载与静载耦合作用下的煤岩体力学试验，分析了动载幅值、预静载对砂岩应变演化、破坏形态和声发射特征的影响。结果表明：扰动荷载导致的损伤程度与预静载水平正相关，高应力状态砂岩在小幅动力扰动荷载作用过程中并不会发生破坏，拉应变呈对数型缓增；高应力状态砂岩在越过应力门槛值的扰动荷载作用过程中发生破坏，破坏前扰动荷载作用周期数随着扰动荷载幅值增加指数型递减；高静应力砂岩破坏前的扰动荷载循环次数随幅值升高而降低。针对研究内容二，自主开发了微型四柱式放顶煤液压支架及其测控系统，并应用于相似模拟试验，研究结果表明：工作面区域会形成“采空区垮落岩体-近场覆岩-液压支架-煤壁”的结构，当下部煤体放出后，组合悬臂结构失去有效支撑，结构破坏并向采空区做回转运动。顶板垮落后对采空区充填不充分，覆岩纵向活动空间较大。随工作面推进，顶煤率先冒放，顶板断裂线先是两侧对称发育，推进一定步距后，工作面前方断裂线呈弧形发育，低位结构率先破坏，其后高位顶板破断掉落至采空区，并最终压实。围绕研究内容三，从相似模拟的角度分析覆岩石结构演化对工作面前方煤体、液压支架、采空区垮落岩体的协同作用的影响。建立了基于煤岩体承载特性的特厚煤层综放工作面支架-围岩耦合数值模拟模型，分析了支架在相同支护强度和不同支护强度下对工作面前方煤体、液压支架以及采空区矸石承载特性的影响。项目研究结果对实现特厚煤层智能化安全高效开采有一定意义。