Numerical simulation of coupled thermo-hydro-mechanical (THM) behavior of buffer material in the China-Mock-up tests at engineering scale
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摘要: 缓冲材料作为填充在废物罐与地质体之间重要的人工屏障，对高放废物处置库的长期安全至关重要。以工程尺度缓冲材料热-水-力多场耦合大型模型试验系统（China-Mock-up）为研究对象，采用有限元数值模拟软件LAGAMINE，考虑试验过程中复杂的边界条件与材料属性，实现了近5 a试验数据的定量模拟。模拟结果可准确预测试验系统内部不同特征点温度随室温周期性波动及线性增长这一动态变化规律；能够较好反映不同特征点相对湿度随时间的行为演化趋势，在加热器附近区域呈现出先干燥后饱和的现象，远离加热器区域则逐渐增大；模拟的总应力与实测试验数据间表现较好地一致性，能够反映试验台架内部不同特征点的总应力随时间逐渐增大这一演化过程。揭示了多场耦合条件下缓冲材料（膨润土）温度、湿度及应力的相互作用关系，为深入认识处置库环境下缓冲材料行为演化特征提供了重要的参考依据。
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关键词:
- 缓冲材料 /
- China-Mock-up试验 /
- 热-水-力多场耦合模拟 /
- 高庙子膨润土
Abstract: The buffer material plays a crucial role in the long-term safety of a high-level radioactive waste repository as it serves as a defense between the waste container and the host rock. To investigate the long-term performance of Gaomiaozi (GMZ) bentonite under repository conditions, based on the China-Mock-up test at engineering scale, the finite element code LAGAMINE is established to establish the THM numerical model. The complex boundary conditions and material properties involved in the test are considered, and the simulated results of temperature, relative humidity and swelling pressure are compared with the experimental ones over the past five years. The temperature in the China-Mock-up test is found to be periodic and linear, primarily influenced by the room temperature, which is accurately captured by the proposed model. Furthermore, the overall variation of the relative humidity at different locations is well reproduced. A desaturation-saturation process is observed in proximity to the heater, while it does not occur far from the heater. Additionally, the simulated results exhibit good agreement with the recorded data, effectively reflecting the increasing trend of stress over time. Besides, the interaction between temperature, humidity and stress of bentonite under the coupled THM conditions is achieved. These findings provide valuable insights into the long-term behavior of buffer materials in a repository environment and serve as an important reference for further understanding.-
Keywords:
- buffer material /
- China-Mock-up test /
- coupled THM model /
- Gaomiaozi bentonite
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图 2 China-Mock-up试验数值模型与网格剖分结果
Figure 2. Numerical model for China-Mock-up experiment and mesh grids
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图 4 饱和度与相对渗透率之间的拟合曲线图
Figure 4. Relative permeability of GMZ bentonite as a function of degree of saturation
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图 5 高庙子膨润土导热系数与饱和度的关系
Figure 5. Thermal conductivity of GMZ bentonite as a function of degree of saturation
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图 7 室温与数值拟合结果随时间的变化
Figure 7. Variation in room temperature and numerical results with time
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图 9 试验台架膨润土内部不同区域特征点温度的模拟结果
Figure 9. Comparison between predictive temperature and experimental results at different locations of China-Mock-up facility
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图 11 试验台架膨润土内部不同区域特征点相对湿度的模拟结果
Figure 11. Comparison between predictive relative humidity and experimental results at different locations of China-Mock-up facility
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图 12 试验台架内部不同时刻水压分布云图（仅显示膨润土块体和破碎颗粒）
Figure 12. Porewater pressure distribution at different times (Only the domains representing compacted bentonite blocks and crushed bentonite pellets are presented here)
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