真三维采动作用下煤岩固气耦合机理及瓦斯运移规律研究

As an extension to the deep coal mining in China with the increase of in-situ stress, gas pressure and the decrease of coal seam permeability, it is more difficult to extract gas of coal seam. Stress redistribution is caused by mining and coal rocks are under the complex stress state of loading/unloading effects simultaneously. Conventional triaxial loading/unloading system is widely used currently to simulate the process of stress changes experienced by the coal rock mass, to study the permeability and mechanics of coal rock mass, which is significantly different with the underground mining environment: true 3D. With the methods of theoretical analysis, experimental research, numerical simulation and engineering validation, this project utilizes the self-developed ‘multi-functional true triaxial fluid-solid coupling experiment system’ and ‘large-scale true 3D simulation device for coal mining’ to establish a true 3D gas-containing failure criterion and a evolution model of coal rock permeability under the dynamic mining stress, to reveal the distribution of diversion fissure area of coal rock fracture and the evolution of dynamic characteristics under the stress state of true 3D mining from the mechanism of stress field, fracture field and coupling of gas flow field under the effects of true 3D mining stress with multi-scale and multi-field angle based on in-situ monitoring and microscopic testing devices such as CT machine. This can optimize the borehole layout of coal seam gas and achieve the high efficient flow-guided of gas, providing theoretical foundation and technical support to further improve the rate of gas drainage and the effect of simultaneous extraction of coal and gas.

随着我国煤炭开采向深部延伸，地应力和瓦斯压力增大，煤层渗透性降低，煤层瓦斯抽采愈加困难。采动引起应力重新分布，煤岩体处于加、卸载同时作用的复杂应力状态。目前多采用假三轴的加、卸载模拟煤岩体所经历的应力变化过程，对煤岩体力学和渗透特性进行研究，这与地下开采环境是真三维的实际情况有较大的差异。本项目通过理论分析、实验研究、数值模拟和工程验证四位一体的研究方法。运用自主研制的“多功能真三轴流固耦合实验系统”和“大型真三维煤岩采掘模拟实验装置”，结合现场监测和CT机等微观检测设备，从多尺度、多场角度研究真三维采动应力作用下的应力场、裂隙场和瓦斯流动场耦合的作用机制，建立真三维含瓦斯煤岩破坏准则和采动应力作用下渗透率演化模型，揭示真三维采动应力作用下煤岩体导流裂隙区域的分布和动态演化特征，优化煤层瓦斯抽采钻孔布置，实现瓦斯高效导向流动。为进一步提高瓦斯抽采率和煤与瓦斯共采效果提供理论依据和技术支撑。

煤炭开采引起应力重新分布，煤岩体处于加、卸载同时作用的复杂应力状态。以往采用伪三轴的加、卸载模拟煤岩体所经历的应力变化过程，对其煤岩体力学和渗透特性进行研究，这与地下煤炭开采环境是真三维的实际情况存在明显差异。本项目通过理论分析、试验研究、数值模拟等研究方法相结合，运用自主研制的“多功能真三轴流固耦合实验系统”、“大型真三维煤岩采掘模拟实验装置”等试验装置，结合现场观测和CT机等微观检测设备，从多尺度、多场角度研究真三维采动应力作用下的应力场、裂隙场和瓦斯流动场耦合的作用机制，建立了真三维含瓦斯煤岩破坏准则和采动应力作用下渗透率演化模型，揭示了真三维采动应力作用下煤岩体导流裂隙区域的分布和动态演化特征，优化了煤层瓦斯抽采钻孔布置，实现了瓦斯高效导向流动。项目研究过程中发表学术论文30篇，其中SCI期刊论文18篇，EI期刊论文7篇，EI会议论文2篇，核心期刊论文3篇；申请国家发明专利8项，获得授权国家发明专利4项；获得省部级一等奖2项；毕业博士1人、硕士8人，其中1人获“重庆市优秀硕士学位论文”；选派了2名博士生分别赴英国和加拿大联合培养；在国际学术会议上宣讲项目研究成果6次。项目研究成果为进一步提高瓦斯抽采率和煤与瓦斯共采效果提供了理论依据和技术支撑。