多场耦合条件下煤岩剪切破坏-渗流耦合机理及煤层瓦斯渗透性研究

The fissures of variety sizes and variety occurrences in coal have been condemned to cause discontinuous, nonlinear, anisotropic and heterogeneity of coal, which also form a channel for flow of gas in coal-seam. It is of great significance to develop studies about the influence of fissure development and evolution of the coal fissures on coal permeability for the efficient extraction of coal-seam gas. This project will be carried out by combining the methods of laboratory experiments, theoretical research and engineering practice. A series of laboratory experiments will be conducted, i.e. studies on the impact of the fissure developing characteristics of the coal pore-fissure structure on coal reservoir gas, researches on the mechanism of structure damage evolution of the complete coal under different shearing loading conditions and the evolution law of permeability, and the shear failure mechanism of fissures and its evolution law of the broken coal under different filling conditions. Based on experimental results above mentioned, the objective of this project is to clarify collaborative relationship between shear-seepage coupling mechanism and the coal-seam gas extraction. Then a coupling model of shear-seepage for coal will be constructed with considering about stress, gas pressure and ambient temperature, thereby revealing the evolution law of deposit and migration of coal-seam gas occurred in original rock stress state under mining conditions. The research results will give guidance on the evolution of gas pressure and its adsorption and desorption states in coal-seam gas extraction as well as providing theoretical support for the effective extraction of coal-seam gas.

煤岩体中产状不同且大小不一的裂隙既导致煤岩呈现非均质、非线性、非连续及各向异性，同时也是煤层瓦斯运移的主要通道。因此，开展煤岩裂隙开裂、扩展、贯通损伤演化机制及其对煤层渗透性影响的研究，对煤层瓦斯高效抽采既具重要的理论研究价值也有实际指导意义。本项目采用实验室试验、理论研究、数值分析与工程实际相结合的方法，在开展煤岩孔裂隙结构发育特征及其对煤层含气性影响、不同尺度条件下压剪荷载作用时完整煤岩结构损伤演化机制及其渗透性演化规律、不同充填条件下压剪荷载作用时破断煤岩体之裂隙面剪切破坏机制及其渗透性演化规律等基础上，阐明煤岩剪切破坏－渗流耦合机理及其与煤层瓦斯抽采之间的协同关系，构建地应力场、瓦斯压力场和环境温度场多场耦合煤岩剪切破坏-渗流耦合模型，揭示原岩地应力状态及采动影响条件下煤层瓦斯赋存与运移演化规律，指导煤层瓦斯抽采中瓦斯压力及其吸附解吸状态演化研究，为煤层瓦斯高效抽采奠定理论基础。

为深入研究煤岩剪切-渗流耦合机理及其与煤层瓦斯抽采之间的协同关系，本项目在系统分析煤岩孔隙结构特征及煤层含气性、煤岩裂隙损伤演化过程规律、煤岩剪切破坏-渗流耦合机理的基础上，以自主研制的多台（套）专用试验仪器设备为主，采用实验室试验、理论研究及工程实际相结合的研究手段，开展了以下研究工作：1）地应力场、瓦斯渗流场和环境温度场多场耦合条件下煤岩体中裂隙的开裂、扩展贯通及煤岩体剪切破坏-渗流耦合机理的应用；2）提出了一系列不同流体注入致岩体剪切力学性质劣化与渗透性耦合作用方式的试验方法，并研发一种新的煤岩剪切-渗流耦合试验装置，用于研究不连续煤岩体在不同流固耦合作用方式条件下的力学特性及破坏机制；3）从地应力，温度，含水率，孔隙压力4个方面着手，进行了大量的三轴渗流试验，就上述因素对含瓦斯煤渗透特性的影响机理进行了系统的理论分析，利用煤层气开采多物理场模拟试验系统，开展了钻孔瓦斯抽采物理模拟试验，研究了抽采过程中的含煤瓦斯渗透性的时空演化，同时针对地应力和初始瓦斯压力对抽采过程中的煤层渗透率演化的影响展开了分析；4）基于煤储层的双重孔隙系统及气、固、液三相共存体系，建立了考虑水分影响和边界条件的渗透率模型，构建了非饱和煤体的应力-应变本构方程、气-水两相连续型方程、能量方程，进而建立了由应力场、渗流场、温度场控制的考虑水分影响的THM耦合模型。