深部动压扰动下煤体致裂诱冲机制的试验研究

In China, rock burst is encountered in many coal mines in recent years, especially those going deeper than about 600 meters, and the problem becomes progressively more severe as the average depth and the extent of mining operations increase. Under the composite efforts of high static stress and dynamic disturbance caused by roof strata rupture, blasting, et al, in deep mining, the trigger mechanism and dynamic response characteristic of rock burst are much complicated, which greatly restricts the forecasting accuracy and controlling efficiency of rock burst. .By comprehensively using the research means of laboratory testing and theoretical analysis, the trigger conditions, multi-field characteristics, et al, will be mainly studied in this project, to reveal the failure and burst-causing mechanism of coal mass under comprehensive effects of strong dynamic disturbance and high static stress. Adoping the coupling static and dynamic characteristic test of burst tendency coal samples and the multi-parameters monitoring, the related critical dynamic stresses to induce rock burst under different static and dynamic loadings will be studied, to reveal the corresponding relations between the static and dynamic stress, as well as the trigger condition of rock burst. In addition, by using the moment tensor inversion of AE events, the crack propagation characteristics of coal samples and the failure mechanisms of macroscopic fractures will be studied, during different coupling static and dynamic loading tests. Furthermore, using the computed tomography (CT) technique, we will study the distribution and evolution of AE wave velocities during the fracturing process of coal samples. Moreover, through the analysis of coupling characteristics between the velocity field, fracturing field, and energy field, the correlation between the wave velocity or velocity gradient and the energy accumulation will be studied, then the evaluation model of burst risk under the dynamic disturbance will be constructed, to provide support for the rock burst forewarning and controlling in deep mining.

受高应力与顶板破断、工程爆破等强扰动的耦合作用，深井冲击矿压事故的频度与危害性愈发严重，其触发机制、动力响应等也更为复杂，极大制约了其预警的准确率与防治的有效性。.本项目采用实验室试验、理论分析等手段，通过研究动压扰动下煤体的孕冲条件、多场量特征等来揭示其致裂诱冲机理。基于动、静组合加载下煤体特性试验与参量监测，研究动压扰动下不同受载煤体冲击失稳的临界动载，确定动压扰动对煤体的冲击触发条件；建立煤体破裂AE源矩张量反演模型，研究动压扰动下不同受载煤体"裂隙场"扩展特征及宏观失稳模式，揭示震源机制差异；建立声波波速CT反演模型，研究不同动、静耦合加载过程中煤体声波"波速场"时空分布；并通过"波速场"与"裂隙场"、"能量场"等场量的耦合特征分析，研究动压扰动下煤体声波波速与能量积聚特征之间的相关性，构建动压扰动下受载煤体的冲击危险评价模型，为预测及弱化控制深部冲击动力灾害提供支撑。

项目采用实验室试验、理论分析、数值模拟等研究方法，基于不同动、静及组合加载的模拟、室内试验及声发射（AE）源、应力等地球物理与力学参量的实时监测与分析，系统研究动压扰动下受载煤岩体的动力响应特征与诱冲致灾机理。.开展不同动静载叠加下煤体动力学响应的模拟试验研究，得出不同受载阶段煤体对于动载峰值动力学响应灵敏度不同，深部煤体承受静载越大，对动载的动力学响应灵敏度较高，诱发煤体冲击破坏的最小动载荷值随静载增加呈负幂函数减小。.试验研究动、静及组合加载作用下煤岩损伤演化与AE参量响应特征。得出随着加载速率增加，试样极限强度提升，对应的应变值降低，加载速率与AE累计撞击数、事件数、振铃数之间具有显著的负幂函数关系，相反，加载速率越高，AE平均能量越高。动静组合加载过程中，首次动载作用时AE信息急剧增加，随着动载循环次数增加，AE振铃产生速率保持稳定，动载持续加载后中，AE信息急剧增加。相同静载条件下，随着动载载荷增加，大能量AE事件明显增多。.基于AE振铃计数，建立煤岩受载的内部损伤模型，提出基于AE振铃的岩石损伤应力-应变本构模型。分析煤岩失稳的AE前兆信息特征，得出AE平均幅值、Ib值、r值一定程度上均可反映试样内部微破裂演化过程，其中r值的异常前兆信息更为突出。.建立煤岩受载过程中AE源矩张量与P、S波位移场的关系模型，建立AE源矩张量分解模型，将矩张量矩阵分解为震源体积变形、轴向拉伸破裂及剪切破裂三部分。以此，分析动、静载及组合作用下煤岩微破裂的震源机制差异。得出不同加载模式下，煤岩体内拉伸、剪切与混合破裂模式同步快速增加，且拉张破裂占大多数；随着加载速率增加，拉张破裂增幅更大，所占比例增加。加载速率提高，岩样破裂形态由剪切破坏转变为竖向劈裂与爆裂破坏。动静组合加载下岩样宏观破裂主要以柱状劈裂为主。.将AE与CT成像技术相结合，利用煤岩受载期间的AE事件作为初始数据进行CT反演，得到试样在各加载阶段的“波速场”分布图像，探究煤岩体内部破裂演化特征。得出波速异常区面积随载荷增加而逐渐扩大并形成贯通，试样宏观破裂位置与波速异常丰富区具有良好对应关系。.以此，总结动、静及组合作用下煤岩损伤与冲击破坏形式，得出动载作用下煤岩可表现为损伤加剧、结构面解锁滑移、自由面反射拉应力等冲击失稳现象。综合考虑煤岩系统的应力、能量、物性及时间等因素，建立动静组合作用下的煤岩冲击判别准则。