A fully coupled hydro–mechanical–chemo model for saturated clayey soils with pore-chemistry-induced and time-dependent deformation

Hydro-mechanical-chemo (HMC) coupling in clayey soils governs the long-term performance of critical infrastructures exposed to chemical environments. Existing models predominantly emphasise the one-way effect of consolidation on solute transport, with the influence of pore-water chemistry on soil deformation remaining insufficiently addressed. This study develops a fully coupled HMC elastic–viscoplastic (EVP) numerical model. It integrates consolidation and solute transport processes by introducing a novel chemical-influenced, time-dependent constitutive relationship. This relationship is formulated as a chemically enhanced EVP (C-EVP) framework by introducing a generalized effective stress concept instead of classical Terzaghi effective stress. The governing equations, rigorously derived from the C-EVP framework, form the core of the proposed HMC model and are solved using an implicit finite-difference scheme. The present solution is further validated against analytical solutions of simplified HMC model for elastic soil and oedometer tests under combined mechanical and chemical loadings. The model successfully reproduces chemically induced compression, volume rebound under salinity reduction, and salinity-dependent creep under constant load. These results demonstrate that the proposed HMC formulation, which explicitly incorporates C-EVP framework, provides a rigorous and reliable tool for predicting long-term settlement and solute evolution in chemically affected clayey soils.