A solute transport in deformable dual-porosity media using mixture-coupling theory

Rock, soil and many porous-like materials are often fractured or structured media, which can exhibit dual-porosity behaviour. Studies on solute transport in deformable dual-porosity media remain challenging due to the multi-physics coupled effects and the complex interaction between fractures (or macropores) and the porous matrix. Although several studies exist on constitutive modelling of coupled behaviour in deformable dual-porosity media, the previously developed models are not systematic in thermodynamical frameworks. This paper proposes a mixture coupling theory approach based on non-equilibrium thermodynamics to develop a solute transport model with consideration of hydromechanical coupling in dual-porosity media (referred to as the ST-HM model). This paper derives the constitutive equations of fully hydromechanical coupled behaviour in dual-porosity media and considers the pore and fracture porosity evolution influenced by both hydraulic and mechanical fields. Therefore, the governing equations of ST-HM are capable of predicting non-reactive solute transport with a fully hydromechanical coupled effect in dual-porosity media. Then, the model was verified against existing models and validated by relevant experimental results. Further, a numerical example shows that the presented model significantly improves the accuracy of the prediction of porosity, fluid pressure and solute concentration compared with previous models, which ignore the fully hydromechanical coupled effects on solute transport.