A thermo-hydro-mechanical coupled model for unsaturated soils based on thermodynamic theory of granular matter

Based on the thermodynamic theory of granular matter and the theory of mixtures, combined with the modified soil water characteristic curve (SWCC) model, considering the granular level energy dissipation caused by changes of temperature and saturation, a new thermo-hydro-mechanical coupled model for unsaturated soils is proposed. The model introduces the concepts of granular entropy and granular temperature. The constitutive relationship of non-elastic deformation can be obtained through the thermodynamic identity. The relationship between the dissipation mechanism of unsaturated soils and the macro-physical and mechanical behavior is established by using the migration coefficients and energy function model. Based on the theoretical model, the thermo-hydro-mechanical (THM) coupling behavior of unsaturated soils is studied. The validity of the model is verified by comparing the simulated results with the experimental data. The results show that the proposed model has the capability to describe the consolidation and shear behavior of unsaturated soils at different temperatures and suctions and the thermal volumetric strain changes under non-isothermal conditions.