This paper is devoted to the study of the Thermo-Hydro-Mechanical (THM) responses of a porous rock with low permeability under thermal loading in the context of deep geological disposal of radioactive waste. To this aim, numerical simulations of a benchmark exercise of a hypothetical high-level radioactive waste (HLW) repository were performed. This benchmark exercise considered as a host formation the Callovo-Oxfordian claystone (COx), which has been selected for a deep geological disposal in France. Within the framework of the DECOVALEX-2019 project, five modelling teams (Andra, LBNL, NWMO, Quintessa, UFZ/BGR) adopted a thermo-poro-elastic approach and proposed different 3D representations of the HLW repository. The differences between the teams consisted mostly in the simplification of the geometrical model and the interpretation of the boundary conditions. Numerical results for temperature, pore pressure, and effective stress evolution in the far field (i.e., at the mid-distance of two HLW cells) were compared between the teams, to quantify the impact of modelling simplifications/assumptions for the assessment of the HLW repository. The THM behaviour of the COx formation in the near field (i.e., excavation damaged zone around the HLW cells) is not the objective of this study. Moreover, plane strain conditions were considered and evaluated in comparison to 3D modelling. Key parameters influencing the THM responses of the HLW repository were assessed by both mono- and multi-parametric analyses. Spatial variability analyses of THM parameters were also carried out to study the influence of the spatial correlation length on the Terzaghi effective stress and to estimate its probability distribution. The conclusions of this study provide reliable numerical techniques for modelling large-scale deep geological disposals and deduce the main behavior of the HLW repository.

本文致力于对放射性废物进行深度地质处置的情况下，在热负荷下低渗透率的多孔岩石的热水力学（THM）响应研究。为此，对假设的高放废物（HLW）储存库的基准演习进行了数值模拟。该基准作业被认为是Callovo-Oxfordian粘土岩（COx）的基质，该岩层已在法国被选作深层地质处置。在DECOVALEX-2019项目的框架内，五个建模团队（Andra，LBNL，NWMO，Quintessa，UFZ / BGR）采用了热孔隙弹性方法，并提出了HLW储存库的不同3D表示形式。团队之间的差异主要在于几何模型的简化和边界条件的解释。在两个小组之间比较了温度，孔隙压力和有效场在远场（即两个HLW单元的中距离）的数值结果，以量化简化模型/假设对HLW评估的影响资料库。本研究的目的不是在近场（即HLW细胞周围的开挖破坏区）中形成COx的THM行为。此外，与3D建模相比，考虑并评估了平面应变条件。通过单参数和多参数分析来评估影响HLW存储库的THM响应的关键参数。还对THM参数进行了空间变异性分析，以研究空间相关长度对Terzaghi有效应力的影响，并估计其概率分布。这项研究的结论为建模大型深部地质处置提供了可靠的数值技术，并推论了高放废物处置库的主要行为。