动静荷载作用下富含瓦斯煤岩扰动破裂机理研究

Over recent years, the coal and rock dynamic disaster caused by high geo-stress, gas pressure and actual mining occur more frequently after the coal mines are being gradually transferred to deep mines.The dynamic disasters that restrict the safe production of coal.Based on the mechanical environment of deep coal-rock under the coupling effect between high in-situ stress and dynamic excavation disturbance and high gas pressure, the experiments on dynamic failure characteristics of gassy coal-rock under coupled static and dynamic loads were conducted with a modified split Hopkinson pressure bar(SHPB). The fracture characteristics of gassy coal-rock under different gas pressure and different static loads have been study by experimental. The numerical simulation method and theoretical analysis are used to study the effects of mechanical properties of gassy coal-rock under dynamic disturbance, which has been coupled mechanical model of stress wave loading and physical model of gas adsorption and desorption. The fracture surface information of fragment under different conditions is analyzed by SEM. So, the failure characteristics of gassy coal-rock under dynamic disturbance are studied by microscopic and macroscopic. Reveal the mechanism of gassy coal-rock failure by distributional dynamic loading. The results can provide a theoretical guide for safe and efficient extraction of deep coal mine.The results have important scientific meaning for the mechanism and control technology of coal or rock dynamic disaster.

深部高瓦斯煤层高强度回采过程中动力灾害日益频繁，严重制约煤矿安全生产。本项目以深部高强度开采煤岩体高地应力、强动力扰动及高瓦斯压力耦合作用的力学环境为背景，拟利用改进后的霍布金逊压杆，对具有不同静应力荷载和瓦斯赋存的煤岩在冲击荷载作用下破坏演化特性进行研究。通过试验得到煤岩在不同静应力荷载和瓦斯赋存情况下的动力扰动破裂特性；结合应力波作用力学模型与煤岩瓦斯吸附-解吸作用物理模型，利用数值模拟和理论分析的方法，综合分析研究含瓦斯煤岩在动力扰动作用下力学特性的影响因素；通过表面形态分析由扫描电镜技术得到的不同工况下试样碎片的裂纹微观信息；从宏细观角度，研究含瓦斯煤岩动力扰动破裂演化特性，揭示在受采动影响的集中动荷载作用下含瓦斯煤岩破裂机理。其研究结果为深部煤炭资源安全、高效回采提供理论依据，对深部开采煤与瓦斯动力灾害灾变机理及防治技术具有重要的科学意义。

含瓦斯煤岩动力灾害是煤矿最为严重的灾害，具有极大的危害性、较强的突发性以及复杂的发生机理等特点，对煤矿的安全生产产生了极大的威胁。本项目在现场采动应力与瓦斯压力监测的结果基础上，利用自行研制带视窗的含瓦斯煤气固耦合力学试验装置及气固耦合动静组合加载实验装置，开展了含瓦斯煤力学特性的实验研究，并利用声发射试验装置对其力学性能和破坏模式进行了试验分析。同时，运用断裂力学理论对含瓦斯试样裂纹尖端应力强度因子公式的进行详细推导，定量地分析了瓦斯压力对含瓦斯煤突变破坏的影响作用。主要结论如下：在回采过程中工作面前方煤体承受上部岩层集中荷载作用，引起局部应力增加。在采动应力影响区域内，受采动应力作用，煤层瓦斯压力明显增大，可增大至残余瓦斯压力的2-5倍。随着初始瓦斯压力的增加，含瓦斯煤样扩容应力和单轴抗压强度逐渐降低，两者比值也随之降低，但扩容量却明显增加。随初始瓦斯压力增加，含瓦斯煤试样在静载及冲击载荷作用下破坏能耗逐渐降低，其内部和表面裂纹分布及破碎块度更为均匀，煤样裂纹进入不稳定扩展阶段的临界应力逐渐降低，破坏模式由脆性破坏转变为塑性破坏。含瓦斯煤裂纹尖端的应力强度因子与初始瓦斯压力密切相关，随初始瓦斯压力增加而增大。因此，在较低的外荷载作用下含瓦斯煤试样极易发生裂纹失稳扩展，最终导致试样强度降低。对于高瓦斯煤层，较小的外部荷载就能造成煤岩失稳突变，所以在含瓦斯煤层开采过程中应特别注意控制高瓦斯煤体的采动应力集中，防止高瓦斯煤层在采动集中应力与高瓦斯压力共同作用下诱发动力灾害事故。