考虑应力-饱和梯度-气压耦合作用下高放废物处置库缓冲/回填材料气体渗透性演化规律及细观机理研究

The evolution law of gas permeability and migration mechanism is one of the key scientific problems for the long-term running safety of the High-Level Radioactive Waste repository. There are still some confusions in the aspects of the experimental and theoretical analyses. In this project, gas permeability test of GMZ bentonite under coupled mechanical-water saturation gradient-gas pressure effect is performed with the THMC seepage test system developed by our group. The evolution law of gas permeability is completely reveled. The characteristics of pore structure evolution of GMZ bentonite is observed by Nuclear Magnetic Resonance (NMR) method combined with X-CT technology. In addition, the internal relationship between pore structure evolution and gas permeability is discussed, and 3D porestructure model is established. Therefore, the meso-mechanism of gas migration can be illustrated deeply. Then, the theoretical model of gas migration in GMZ bentonite is developed, and it is embedded in the finite element program to simulate the gas tightness of buffer/backfill materials. Finally, the system of gas tightness evaluation is established to supply the technical support for the assessment of the gas tightness and long-term running safety of the artificial barrier system of High-Level Radioactive Waste repository.

缓冲/回填材料（膨润土）气体渗透性演化规律及机理是高放废物深地质处置长期安全性评价的关键科学问题之一，至今仍未从实验和理论方面统一认识。本项目拟利用自行研制的温度-渗流-应力-化学多场耦合渗流测试系统，开展GMZ膨润土在应力-饱和梯度-气压耦合作用下气体渗透性试验研究，全面揭示多场耦合因素作用下气体渗透性演化规律；结合X-CT扫描和核磁共振细观观测技术，明确多场耦合因素下GMZ膨润土孔隙结构演化特征，探讨细观孔隙结构与气体渗透性之间的内在联系，建立细观三维孔隙结构模型，深入阐明气体渗透演化细观机理；建立多场耦合因素作用下气体在GMZ膨润土中渗透理论模型，并嵌入到有限元程序中，对处置库缓冲/回填材料气密性进行仿真分析；最终，建立处置库缓冲/回填材料气密性评价体系，为我国高放废物处置库人工屏障系统气密性和长期运行安全性评估提供技术支持。

项目以我国高放废物深地质处置使用的缓冲/回填材料-高庙子膨润土-为研究对象，利用自行研制的温度-渗流-应力-化学多场耦合渗流测试系统，开展了GMZ膨润土在应力-饱和梯度-气压耦合作用下气体渗透性试验研究，揭示多场耦合因素作用下气体渗透性演化规律；结合细观观测技术，明确了多场耦合因素下GMZ膨润土孔隙结构演化特征，探讨细观孔隙结构与气体渗透性之间的内在联系，建立细观三维孔隙结构模型，深入阐明了气体渗透演化细观机理；建立了多场耦合因素作用下气体在GMZ膨润土中渗透理论模型，并对膨润土气水运移特性进行仿真分析；相关结论可以为我国高放废物处置库膨润土屏障系统气密性评价提供技术支持。