Abstract In a deep geological repository (DGR) for the long-term containment of radioactive waste, gases could be generated through a number of processes. If gas production exceeds the containment capacity of the engineered barriers or host rock, the gases could migrate through these barriers and potentially expose people and the environment to radioactivity. Expansive soils, such as bentonite-based materials, are currently the preferred choice of seal materials. Understanding the long-term performance of these seals as barriers against gas migration is an important component in the design and long-term safety assessment of a DGR. This study proposes a mathematical hydro-mechanical (HM) model for migration of gas (two-phase flow) through a low-permeable heterogeneous swelling geomaterial. It is based on the theoretical framework of poromechanics, applies Darcy's Law for both the porewater and poregas, and incorporates a modified Bishop's effective stress principle. The study expands upon previous work by the authors, by assessing three stress-strain constitutive models in an attempt to simulate dilatancy-controlled gas flow; i) an enhanced elastic damage model, ii) an elastoplastic model with damage, and iii) a non-local elastoplastic model with damage. Using the Finite Element Method (FEM), the models were used to simulate axial and radial flow through a low-permeable swelling soil. The results were validated against experimental results found in the current literature for a confined cylindrical sample of near-saturated bentonite under a constant volume condition. This study provides insight into the use of highly coupled HM models, their influence on the stress state of the material, and their capabilities to represent multi-phase flow in a swelling geomaterial.

中文翻译：

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研究代表膨胀地质材料中气体输运的模型

摘要 在用于长期封存放射性废物的深地质处置库 (DGR) 中，气体可能通过多种过程产生。如果天然气产量超过工程屏障或围岩的容纳能力，气体可能会迁移通过这些屏障，并可能使人和环境暴露于放射性之下。膨胀土，例如基于膨润土的材料，是目前密封材料的首选。了解这些密封件作为防止气体迁移的屏障的长期性能是 DGR 设计和长期安全评估的重要组成部分。本研究提出了一种数学流体力学 (HM) 模型，用于气体迁移（两相流）通过低渗透性异质膨胀地质材料。它基于多孔力学的理论框架，对孔隙水和孔隙气均应用达西定律，并结合修改后的 Bishop 有效应力原理。该研究扩展了作者之前的工作，通过评估三个应力应变本构模型以试图模拟膨胀控制的气流；i) 增强的弹性损伤模型，ii) 具有损伤的弹塑性模型，以及 iii) 具有损伤的非局部弹塑性模型。使用有限元方法 (FEM)，这些模型用于模拟通过低渗透膨胀土壤的轴向和径向流动。结果与在当前文献中发现的在恒定体积条件下的近饱和膨润土的受限圆柱形样品的实验结果进行了验证。这项研究提供了对高度耦合 HM 模型使用的见解，