应力-渗流耦合作用下含瓦斯煤体的渗透演化规律及其损伤机理研究

The permeability evolution model for describing the permeability evolution mechanism of coal containing gas has not been unified, and the stress- seepage-damage mechanism requires further explanation, so this project is put forward. The gas-solid coupling true triaxial seepage test device and the shear test box are researched and development independently. The intermediate principal stress and incoordinate normal stress are added as variables. The mechanics and permeability test of coal are designed under different boundary conditions with acoustic emission automonitoring system. The mechanical properties, seepage characteristics and damage evolution law are researched by these test, and the stress- seepage-damage coupling effect model will be established. The digital coal model can be imported to the PFC3D software based on the digital coal model which can represent the real pore structure of coal established by CT three-dimensional reconstruction technology, as well as the help of the reverse engineering technology. the damage mechanism of coal under the coupling effect of stress- seepage can be researched by the coupled numerical simulation analysis. According to the contrastive analysis of physics experiment, the reasonability of the use of PFC3D numerical simulation in the research of stress-seepage mechanism of coal containing gas can be verified, and the stress- seepage-damage coupling effect model can be revised. The permeability evolution law and damage mechanism of coal containing gas under the coupling effect of stress- seepage will be revealed finally.

本项目针对尚未有统一的含瓦斯煤体渗透演化模型以及应力-渗流-损伤机理需进一步阐释提出的。首先，利用自主研制的气-固耦合真三轴渗流试验装置及剪切试验盒，增加中间主应力和不对等法向应力为变量，进行不同边界条件下煤体力学及渗透特性实验，结合声发射监测系统对含瓦斯煤力学、渗流特性及损伤演化规律进行研究，构建含瓦斯煤体应力-渗流-损伤耦合作用模型；同时，基于CT三维重构技术建立的能够表征真实孔隙结构的煤体数字模型，结合逆向工程技术，实现煤体数字模型向PFC3D软件的导入，从细观角度进行煤体损伤特性及瓦斯渗流规律的耦合模拟分析，探究煤体应力-渗流耦合损伤机制；最后，通过与物理实验结果对比，验证基于煤体真实孔隙模型的PFC3D数值模拟用于分析含瓦斯煤体渗流-损伤耦合机理的准确性，并对所建立的含瓦斯煤体应力-渗流-损伤耦合本构模型进行修正，从而揭示应力-渗流耦合作用下含瓦斯煤体渗透演化规律及其损伤机理。

本项目阐释了含瓦斯煤体渗透演化模型以及应力-渗流-损伤机理。首先，结合CT三维重建技术和核磁共振实验，实现了煤体孔裂隙结构的定量表征，并建立了煤的三维孔、裂隙结构模型和具有拓扑结构的孔隙网络简化模型；其次，利用自主研制的气-固耦合真三轴渗流试验装置及剪切试验盒，增加中间主应力和不对等法向应力为变量，进行不同边界条件下煤体力学及渗透特性实验，结合声发射监测系统对含瓦斯煤力学、渗流特性及损伤演化规律进行研究，构建含瓦斯煤体应力-渗流-损伤耦合作用模型；同时，基于CT三维重构技术建立的能够表征真实孔隙结构的煤体数字模型，从细观角度进行煤体损伤特性及瓦斯渗流规律的耦合模拟分析，探究煤体应力-渗流耦合损伤机制；然后，利用DEM数值模型揭示了双轴压缩条件下含两个预制裂隙煤样裂纹扩展细观力学行为。最后，通过共轭传热模拟和热变形模拟，发现了孔裂隙结构对于流动速度和温度分布的影响规律。以上研究有效揭示了应力-渗流耦合作用下煤体结构变化特征及含瓦斯煤体渗透演化规律及其损伤机理。