Multiphysics model of swelling geomaterials based on Stern theory: Describing different swelling behaviors depending on exchangeable cation species

Limited models have been devised using Stern theory to obtain the repulsive force from a double layer. Moreover, an elastoplastic model that differentiates various swelling behaviors because of exchangeable cation species is yet to be devised. In this study, we introduce a novel multiphysics elastoplastic model for swelling geomaterials that incorporates Stern theory. This model considered the finite size of exchangeable cations and specific adsorption phenomena, which are typically overlooked in existing models. Based on Stern theory, we derived the repulsive force from the double layer and integrated the force into the elastoplastic expansive bedrock model, which addresses electro–chemo–mechanical phenomena in the interlayer. The proposed model differentiated swelling behaviors based on the type of exchangeable cation species by incorporating these phenomena. To validate the model, a one-dimensional (1D) numerical analysis was performed, demonstrating its capability to describe various swelling behaviors due to different exchangeable cation species through comparison with free swelling test results of bentonite. Additionally, a parametric study was conducted to elucidate the effect of the hydrated radius of exchangeable cations and the specific adsorption potential on swelling behavior, analyzed from the perspective of the equilibrium of charge distribution near the mineral surface. • A multiphysics elastoplastic model of swelling geomaterials based on Stern theory. • Distinguish different swelling behaviors owing to exchangeable cation species. • 1D calculations for different swelling behaviors for exchangeable cation species. • Comparisons with the experimental results of Ye et al. (2017). • Parametric study clarified effects of ion size and specific adsorption on swelling.