受载煤体裂隙场和瓦斯渗流场耦合的实验及理论研究

In the project the distribution and evolution law and the coupling relationship of mesoscopic fracture field and gas seepage field of coal during the loading process are studied. The main contents include: the development of CT scan system of gas seepage in coal under condition of loading. The dynamic evolution law of coal fracture through the CT scanning test and the effect of fracture to the gas flowing and the distribution and evolution law of fracture in Coal containing gas is studied by CT scan system when it was loaded. The relationship between the crack and seepage field is analyzed and the coupling theory model between fracture field and gas seepage field is established which reveal the mechanism of gas seepage. The effect law of coal dynamic, gas desorption and diffusion, and the mechanism of gas seepage is analyzed by use of simulation and experimental results. The peek experiment of the roof of the roadway is done in coal mine and the experimental and numerical simulation result is verified. To observe the spatial and temporal characteristics of the fracture field of the working face and the roadway through drilling peep instrument on site, and analyze the interrelation between the fracture field and the gas seepage field, and optimize the best characters of the drainage hole. The research achievements can be the theory support in raising the drainage rate in coal mines.

本项目通过实验和理论方法研究煤体在加载过程中细观裂隙场、瓦斯渗流场的分布及演化规律、相互作用和耦合关系，主要内容包括：建立完善受载条件下的煤体瓦斯渗流的CT扫描实验系统；利用受载煤体CT扫描实验系统研究煤体分级加载和循环加载过程中煤体裂隙场的动态演化规律及加载过程中细观裂隙场对瓦斯渗流的影响规律、加载渗流全过程的细观裂隙场分布及演化规律；理论分析裂隙场和渗流场的关系，建立煤体裂隙场与瓦斯渗流场的耦合理论模型，揭示细观瓦斯渗流机制；利用理论分析并结合数值模拟结果，结合实验室研究结果分析煤体的力学和瓦斯解吸扩散、渗流的影响规律，分析渗流机理；在煤矿现场利用钻孔窥视仪对采掘空间煤岩体随推进过程进行裂隙场时空特征进行观测，分析裂隙场和瓦斯流动场的相互关系，优化抽放钻孔最佳参数。研究成果可以为煤矿瓦斯抽放率的提高提供理论支持。

开展了受载煤体CT扫描、声发射、瓦斯渗流实验，研究了不同加载方式下的煤体微观裂隙场的时空演化规律和瓦斯渗流规律。结果表明，煤岩受载对细观变形影响显著并呈非线性，将卸载过程开始出现明显的声发射现象定义为后Kaiser效应，三种应力加载路径条件下渗透率的变化趋势基本一致，煤体的非弹性变形增大，煤体的孔隙裂隙增多，渗流通道增多，从而渗透率变大。借助SEM、液氮吸附与CT扫描相结合的方法，分析不同矿区煤样孔隙结构特征，揭示了煤体纳米孔隙结构特征与受载细观变形规律，即煤体在加载过程中初始变形快，空间上煤体内部局部呈现膨胀效应，局部呈现收缩效应，但是在整体上表现是膨胀的，这是由煤体的非均质特性决定的。建立多孔介质条件下瓦斯渗流耦合模型，采用数值模拟方法，煤体裂隙场和渗流场随应力场的变化规律，提出了前视钻孔窥视视频提取钻孔信息的方法。利用图像处理等方法定量分析了裂隙场演化规律并三维重构再现了裂隙场发育过程，该技术应用于裂隙带钻孔参数的确定。