剪切荷载作用下煤岩裂隙细观演化及其对瓦斯渗流的影响研究

Coal is used as the most important resource in China. As a associated product in coal, gas is not only a valuable clean energy, but also it is considered as a major disaster source of coal mine. Therefore, obtaining coal together with gas safely and efficiently is necessary for the mining exploitation of coal resources in the deep area.This project mainly focuses on the gas-coal rock coupling mechanism, especially the evolution process of effective percolation network caused by the rupture of coal and rock, as well as the coupling effect between the evolution of percolation network and percolation and desorption of gas. In the physical experiment, self-developed electro-hydraulic servo-control compression shear-seepage device of coal containing methane was used. In order to better understand the evolution laws of shear microcracking in the coal rock containing-gas and its control mechanism for the percolation of gas, the properties of native hole cracks structure in coal reservoir, the main factors of containing gas and the evolution laws of shear microcracking and expansion of gas-containing coal under compression-shear load condition were studied. The percolation characteristics of coal rock containing-gas in the expansion process of the shear crack were studied also. Synchronously, the relationship between the characteristic parameters of percolation network and permeability of coal containing-gas was established. By building a gas percolation model based on the above relationship, numerical simulation method was used for the analysis of mining exploitation of coal-bed. The explaining of coupling mechanism between the evolution progress of shear microcracking and gas migration in the coal rock can provide a scientific basis for the efficient exploitation of gas and coal together.

瓦斯作为煤的伴生产物，既是煤矿重大灾害源，也是一种宝贵的清洁能源。实现煤与瓦斯安全高效共采，是深部煤炭资源开采的必然途径。项目围绕煤与瓦斯共采中的瓦斯-煤岩流固耦合作用机制这一关键科学问题，并重点着眼于煤岩剪切破断过程中有效渗流网络演化及其与瓦斯解吸、渗流之间的耦合作用规律，通过自制电液伺服控制含瓦斯煤压剪-渗流试验装置，从细观角度，开展煤储层原生孔裂隙结构特征及其含气性主控因素、剪切荷载作用下含瓦斯煤岩裂隙开裂扩展细观演化规律及剪切裂纹开裂扩展过程中含瓦斯煤岩渗流特性等方面的试验研究工作，探明煤岩裂隙细观演化规律及其对煤层含气性及瓦斯渗流的控制机制。并构建含瓦斯煤渗流网络细观特征参数及其与渗透率之间的关系，在此基础上建立耦合渗流网络特征参数的瓦斯渗流模型，通过数值模拟方法将建立的模型应用到煤层开采分析中，揭示煤岩体裂隙演化与瓦斯运移耦合作用机理，为煤与瓦斯安全高效共采提供科学依据。

实现煤与瓦斯安全高效共采，是深部煤炭资源开采的必然途径。项目围绕煤与瓦斯共采中的瓦斯-煤岩流固耦合作用机制这一关键科学问题，开展了煤岩剪切破断过程中有效渗流网络演化及其与瓦斯解吸、渗流之间的耦合作用规律研究，取得的主要进展如下：1) 分析了煤岩原生孔裂隙结构特征，并利用HCA型高压容量法吸附装置对其吸附瓦斯特性进行了试验研究，得到了不同温度下的等温吸附曲线及吸附常数a、b值随温度的变化规律；2) 基于自主研制的含瓦斯煤岩细观剪切试验装置，提出了含瓦斯煤岩细观剪切试验方法，并依此进行了不同瓦斯压力、不同加载速率、不同正应力条件下的含瓦斯煤岩剪切试验，揭示了剪切面裂纹的时空演化规律及其断裂力学机理，建立了剪切面裂纹分形维数与断裂耗散能之间的关系方程；3) 提出了煤岩剪切细观开裂演化特征量化参数，对煤岩剪切细观开裂演化特征进行了量化分析；4) 利用自主研发的含瓦斯煤热流固耦合三轴伺服渗流实验装置，开展了不同采动应力条件下煤岩应力-裂隙-渗流耦合特性的试验研究，并利用COMSOL Multiphysics与UDEC数值模拟软件相结合的方法进行了相关数值模拟研究，阐明了采动煤岩应力-裂隙-渗流耦合机制；5) 自主研制了煤岩剪切–渗流耦合试验装置，该装置包括伺服控制加载系统，流体源加载系统，剪切盒及其密封系统，控制与数据采集系统，煤岩断面三维扫描系统5个部分，可应用于开展原岩地应力状态及采动影响条件下煤层内部煤岩剪切破断过程及其与煤层瓦斯渗透性耦合机制的试验研究。