Bentonite is a key material for the construction of Engineered Barrier Systems (EBSs) in deep geological repositories (DGRs) for radioactive waste. Modelling of gas migration in saturated bentonite, as well as the accompanied hydromechanical (HM) processes is crucial for conducting a performance assessment for the safety of a deep geological repository (DGR). The objective of this paper is to review the state-of-the-art of coupled HM models for simulating the gas migration behaviors in saturated bentonite. To this end, the paper has reviewed and discussed the coupled HM models from several aspects, including governing equations, HM constitutive models, fracture theories and related numerical approaches. Moreover, these models are discussed in terms of their merits and limitations to simulate the observed experimental behaviors. It is found that the previous HM models were generally established in the framework of Biot's consolidation theory or mixture theory. The adopted mechanical models include linear/nonlinear elastic models, elastoplastic models, damage models and swelling models. The incorporation of plastic and damage models into the coupled HM framework has enabled to account for the effect of the development of preferential pathways. However, these mechanical models don't enable to explicitly simulate the preferential pathways. The gas flow in saturated bentonite has been generally modelled by the generalized Darcy's law. Visco-capillary two-phase flow model with enriched intrinsic permeability (gas-pressure-based model, porosity-based model, strain-based model, damage-based model, Embedded Fracture Model, EFM) is the most used hydraulic model to simulate the gas flow. The EFM and its variations are the most widely used permeability models to simulate the gas migration process in saturated bentonite. The development of preferential pathways has been commonly considered in an implicit way by using the embedded fracture model as intrinsic permeability model or by adopting plastic or damage models to describe the mechanical behaviors. Current numerical models that can explicitly simulate the gas-driven fracturing process in saturated bentonite were not frequently reported. The existing ones are not complete enough to simulate all the key experimental behaviors associated with the preferential pathways. Advanced numerical approaches, such as XFEM or DEM based approaches, and proper fracture theories, such as the cohesive zone model, need to be employed to explicitly describe the development of preferential pathways. At the end of this paper, conclusions and recommendations for future modelling studies on gas migration in bentonite barrier are given.

膨润土是在放射性废物的深层地质处置库（DGR）中构造工程屏障系统（EBS）的关键材料。对饱和膨润土中的气体运移以及伴随的水力机械（HM）过程进行建模对于进行深层地质处置库（DGR）的安全性性能评估至关重要。本文的目的是回顾用于模拟饱和膨润土中气体迁移行为的耦合HM模型的最新技术。为此，本文从多个方面对耦合的HM模型进行了回顾和讨论，包括控制方程，HM本构模型，断裂理论和相关的数值方法。此外，就它们的优点和局限性来讨论这些模型，以模拟观察到的实验行为。发现以前的HM模型通常是在Biot固结理论或混合理论的框架内建立的。所采用的机械模型包括线性/非线性弹性模型，弹塑性模型，损伤模型和溶胀模型。将塑性和破坏模型纳入耦合的HM框架已能够说明优先途径发展的影响。但是，这些机械模型无法明确模拟优先路径。饱和膨润土中的气体流动通常已通过广义达西定律建模。具有丰富的固有渗透率的粘性毛细管两相流模型（基于气压的模型，基于孔隙率的模型，基于应变的模型，基于损伤的模型，嵌入式断裂模型，EFM）是最常用的模拟气体流动的水力模型。EFM及其变体是使用最广泛的渗透率模型，用于模拟饱和膨润土中的气体运移过程。通常通过将嵌入式裂缝模型用作内在渗透率模型，或采用塑性或破坏模型来描述力学行为，以隐含方式考虑优先路径的开发。可以明确模拟饱和膨润土中气体驱动压裂过程的现有数值模型并不经常报道。现有的还不够完整，无法模拟与优先途径相关的所有关键实验行为。先进的数值方法（例如基于XFEM或DEM的方法）以及适当的断裂理论（例如内聚区模型）需要用来明确描述优惠途径的发展。在本文的最后，给出了对未来膨润土屏障中气体运移模型研究的结论和建议。