煤巷开掘加卸载路径下的冲击孕育机理与危险性判识

Due to the high stress around the entry, drastic loading-unloading process, dynamic disturbance, etc., the occurrences of rock bursts during coal entry excavation in deep coal mines are increasing rapidly, which always result in catastrophic consequences. Therefore, this project focuses on the preparation process of rock burst during the coal entry excavation, and a systematic research will be conducted on rock burst inducing mechanism and hazard assessment of coal entry under different loading-unloading paths. Based on triaxial loading-unloading tests and parameters monitoring such as stress, acoustic emission (AE), etc., the fracture mechanism characteristics and energy evolution law of coal mass under different loading-unloading paths will be investigated, multiple AE precursor information of coal mass under pressure such as fracture development, wave velocity distribution, etc. will be analysed, and the focal mechanism and burst failure mode of coal mass in microscopic and macroscopic view will be recognized. By using numerical simulation, the influence law of stress and geological environment, stress paths etc. to the dynamic response in coal entry excavation will be analysed, the key factors of rock burst hazard will be selected. Combining with the laboratory test and simulation results, the discriminant criterion for inducing rock burst in coal entry excavation will be proposed by energy analysis. Based on weight quantification of excavation key factors using triangular fuzzy matrix and space-time-intensity information response of microseismicity during entry excavation, the comprehensive index method for rock burst risk assessment before excavation and the probability model of microseismic multiple information for dynamic pre-warning during excavation will be proposed, respectively. The outcomes of the project can provide references to the prediction and alleviation of rock bursts during coal entry excavation.

受高应力、强卸载或动载荷等复杂力学环境影响，我国深部煤巷开掘冲击地压事故的频度与危害愈发严重。针对这一现状，项目以煤巷开掘冲击孕育过程为核心，系统开展不同开掘加卸载路径下的煤体冲击触发机理与危险性判识预警研究。基于真三轴动静加卸载试验与应力、AE等参量监测，研究不同加卸载及卸载-动载路径下煤体破裂力学特征与能量演化分配规律，分析煤体受载过程中“裂隙场”扩展、“波速场”分布等AE多元前兆信息，辨识煤体宏微观震源力学特性与冲击失稳类型；离散元模拟分析应力与地质环境、应力路径等对煤巷开掘围岩动态响应的影响规律，筛选冲击危险主控因素，结合室内实验与细观模拟，提出基于能量分析的煤巷开掘诱冲判别准则；基于三角模糊数的开掘主控因子权重量化与工程微震时空强多元信息响应，提出冲击危险掘前预评价的综合指数方法及掘中动态预警的微震多信息概率模型。通过项目研究，为预测及弱化控制煤巷开掘冲击动力灾害提供参考。

项目综合采用了现场调研与监测、实验室试验、数值模拟、理论分析等研究方法，系统开展了不同煤巷开掘应力路径下煤岩变形破裂机制、能量演化规律分析与结构失稳模式辨识、开掘加卸载响应的影响规律、多尺度物理场响应特征分析与冲击危险判据、风险评价与预警模型构建等一系列研究工作。.开展了真三轴不同加卸载路径下煤体动力学响应的试验研究，得到真三轴中、低载荷受载煤样在各方向均呈现出压缩状态，但随着最大主应力与中间、最小主应力逐渐增加，最小主应力方向与中间主应力方向相继出现扩容现象。在真三轴加载初期，原生孔隙逐渐闭合与原生致密区的初始受载使此阶段煤样内出现少量的高、低波速区。随着载荷逐渐增加，原生孔隙压实与致密区破裂造成高波速区转移扩展与波速异常区形成。在真三轴高载荷保压阶段，由于煤样裂隙的不断压实与内部结构特征的充分破坏，煤样内出现以低波速区不断减小与整体波速提高为代表的持续性损伤。同时，在低载荷水平下，煤样内主要以张拉破裂为主，随着载荷水平不断增加，微破裂类型逐渐转变为剪切破裂，同时破裂数量在保压阶段的上升速度有明显增加。.构建了巷道开挖的UDEC离散元模型，模拟煤巷掘进卸载作用过程，结果表明，煤巷掘进冲击显现需要一定的应力水平；掘进卸载作用下冲击破坏的能量主要源于煤体自身积聚的弹性应变能。研究了地应力、顶底板岩性、煤厚和巷道位置对煤巷掘进卸载作用下冲击地压显现规律的影响。得出在相同侧压系数时，应力水平越高，冲击破坏释放能量越高。研究了动载因素对煤巷掘进卸载作用下冲击地压显现规律的影响。得出应力波幅值越大，冲击释放能量越大，巷道破坏越严重。.分析了煤巷掘进冲击地压危险的主要影响因素，结合调研资料构建了煤巷掘进冲击地压实例数据库，基于三角模糊数原理，构建了煤巷掘进冲击地压危险预评估综合指数模型；结合室内小尺度煤样加卸载冲击前兆信息，建立了掘进冲击地压的微震多信息概率预警模型与方法。