高瓦斯煤层巷道锚固区围岩承载能力弱化及失稳机理研究

In order to investigate the surrounding rock control problem in high containing-gas coal, the low field nuclear magnetic resonance technique is used to explore the pore sizes, the crack growth and the gas isothermal adsorption and desorption characteristics for microstructure considerations. The failure mechanism of the coal, the reasons for a decreasing bearing capacity caused by weakening of the mechanical properties and the instability mechanism of the coal under high gas are then investigated. The main research contents are as follows. The low field nuclear magnetic resonance technique is used to explore the porosity, the crack growth and the gas isothermal adsorption and desorption characteristics for microstructure considerations.The microstructure of the pores, the permeability and the coal deformation characteristics under high gas pressure are analyzed. Influences of the gas pressure on the microstructure of the pores and the coal deformation are also discussed. Moreover, the T2 spectrum and the nuclear magnetic resonance imaging methods are performed to analyze and evaluate the coal damage extent and the crack growth characteristics. The weakening mechanism of the coal bearing foundation and the reasons for a decreasing bearing capacity caused by weakening of the mechanical properties are analyzed and discussed. This research would provide a usefully theoretical guide for the roadway support in high containing-gas coal.

针对高瓦斯煤层巷道围岩控制问题，采用低场核磁共振技术从微观结构研究煤体孔隙孔径、裂隙发育以及瓦斯等温吸附解吸特征，进而研究煤体在瓦斯作用下的破坏机理，揭示瓦斯作用下煤体承载基础力学性能弱化及失稳机理，为高瓦斯煤层巷道支护提供理论基础。主要研究内容有：（1）采用低场核磁共振技术从微观结构研究煤体孔隙孔径、裂隙发育、孔隙度以及瓦斯等温吸附解吸特征；（2）通过T2谱和核磁共振成像定量分析评价煤体损伤程度、裂隙发育特征及煤体的力学损伤程度，研究瓦斯压力对煤体微观孔隙结构、渗透率以及煤体变形特征的影响规律；（3）揭示锚固区煤体性能劣化引起的煤层承载基础弱化及承载能力下降机理。

由于现有的支护理念和支护技术由于没有考虑瓦斯对煤体物理力学性能影响，在一定程度上已经不能满足高瓦斯煤层巷道支护要求，本课题基于高瓦斯煤层巷道支护特点，通过实验分析、理论分析和数值模拟方法分析，采用目前国内最先进的低场核磁技术对瓦斯渗流作用下的煤体物理力学性能进行试验研究，结合宏观力学理论，探索高瓦斯煤体破坏演化规律，得到煤岩物性参数及形变规律，围压加载及卸荷过程对煤体微观孔隙的特征，构建瓦斯压力与煤体强度的力学耦合关系，推导出高瓦斯煤层巷道围岩塑性区半径计算公式，建立锚固区瓦斯压力作用下围岩承载强度模型，进而对高瓦斯煤层巷道锚固区围岩承载基础弱化及引起的失稳机理进行研究，对指导高瓦斯煤层巷道支护具有重要理论及工程实际意义。