基于微细观结构演化的T-M损伤硬岩气体渗透性研究

This research is in the context of sealing property of the excavation damaged zone (EDZ) in the high-level radioactive waste (HLW) geological disposal project. In general, it is based on the theory of poromechanics, mesocracking and percolation of porous media. In this project, innovative experimental simulation design, 3D micro image analysis, and seepage simulation will be employed to analyze real-time multi-scale pore network evolution and seepage, and then the mechanism is preliminarily discussed. Based on the evolvement of macro-meso mechanical behavior and micro pore characteristic under coupled effects of thermo-mechanical, the relationship between real-time coupled damage and corresponding gas permeability will be correlated, and discussed. Afterwards, the relationship between macro gas permeability and meso poromechanical parameters will be proposed. Finally, according to 3D image analysis, multi-scale pore structure of thermo-mechanical damaged EDZ granite will be reconstructed. The fluid seepage process will be simulated and its variation along with pore characteristics will also be analyzed by lattice Boltzmann method, thus revealing the mechanism between coupled damage and permeability for HLW disposal. All the research will provide scientific foundation to quantitatively analyze more complex coupled issues and multi-scale effects on the long-term safety analysis of HLW disposal, and other hard-rock underground engineering fields.

本项目以高放废物地质处置工程开挖损伤区（EDZ）围岩密封性为研究背景，以多孔介质力学、渗流理论、均匀化理论为基础，采用宏观渗流与细观力学试验设计、3D微细观图像分析与渗流模拟相结合，对热-力（T-M）耦合损伤围岩微细观孔结构、实时渗流特征进行探讨。研究从耦合因素对围岩细观多孔介质力学行为、微细观孔隙特征作用出发，分析耦合损伤对孔结构演变的作用机制，揭示损伤的细观力学行为演变与实时气体渗透率的关联。基于X-CT图像扫描，定量分析实时T-M耦合损伤孔结构特征、构建微细观孔隙模型，借助宏观格子Boltzmann法模拟流体在损伤岩体孔隙裂纹内的渗流特征，深度剖析微细观孔结构演变对渗透性的影响，揭示实时耦合损伤对渗透性的影响机制。上述研究成果为定量分析高放废物处置库EDZ围岩密封性提供科学依据，为解决更为复杂的多场耦合条件下地下硬岩洞室长期安全性评价提供借鉴依据。

热、力、水及化学场多场耦合作用下硬岩的微细观结构演化规律是地下洞室渗流传输性能评价的关键科学问题之一，是岩石力学研究的热点与难点问题之一。依托高放废物深地质封存、干热岩开发利用及TBM硬岩条件下海底隧道修建过程中的多场耦合传输问题，本项目研究了耦合损伤对岩石孔结构演变的作用机制，揭示了损伤的细观力学行为演化与实时气体渗透率的关联。基于低场核磁共振技术(NMR)，剖析页岩层理面对微裂缝萌生的影响，揭示了耦合损伤对渗透性的影响机制。上述研究成果为解决复杂的多场耦合条件下地下硬岩洞室长期安全性评价提供了借鉴依据。