Derivation of heterogeneous material distributions and their sensitivity to HM-coupled two-phase flow models exemplified with the LASGIT experiment

• Published in: Environmental earth sciences Vol. 82; no. 14; p. 347
• Main Authors: Radeisen, Eike, Shao, Hua, Pitz, Michael, Hesser, Jürgen, Wang, Wenqing
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2023; Springer Nature B.V; Springer-Verlag
• Subjects: Bentonite; Biogeosciences; Continuum modeling; Dilatancy; Earth and Environmental Science; Earth Sciences; Environmental Science and Engineering; Environmental Sciences & Ecology; Finite element method; Fractures; Gas flow; Gas transport; Geochemistry; Geology; Hydrology/Water Resources; Localization; Material properties; Mathematical models; Mercury; Microfracture; Microstructure; Modelling; Multiphase flow; Numerical models; Original Article; Porosity; Radioactive materials; Repositories; Stochasticity; Terrestrial Pollution; Two phase flow; Water Resources; M coupling; Gas migration; Continuous approach; H; Dilatancy-controlled flow; LASGIT experiment; Geomaterial heterogeneity; OpenGeoSys
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-023-11004-z

Advective gas transport in bentonite, a possible buffer material in repositories for radioactive materials, is difficult to simulate in numerical continuum models, partly due to the complicated microstructure of bentonite. To generate reliable models of repositories nevertheless, spatially distributed heterogeneous material properties can be used to allow localization of gas flow. In this study, a pore-size-dependent stochastic approach of the gas entry pressure is derived from Mercury Intrusion Porosimetry, which is used to replicate measurements from the LASGIT experiment. In addition, three benchmark tests are simulated to investigate the dependence of heterogeneous distributions of material properties on the mesh discretization, the temporal dependence, and the coupling between the processes influenced by the heterogeneous parameters. The numerical modeling results of the LASGIT experiment show that the onset of gas flow into the system and the subsequent increase in pressure and stress can be well reproduced using heterogeneous distributions. Compared to a model with homogeneous material properties, heterogeneous distributions may allow the generation of dilatancy-controlled microfractures—an important feature with regard to the advective gas flow in bentonites. However, it can be observed that the heterogeneous distributions in LASGIT are less significant, as technical gaps or differences in material types could have a greater impact.