On the thermo-mechanical properties of unsaturated soils

The establishment of energy balance equation is necessary to study the thermo-mechanical properties of unsaturated soils. To solve this equation, the determination of two fundamental parameters as volumetric specific parameter and thermal conductivity coefficient is essential. In this paper, the effective thermal conductivity coefficient of dry soil grain is analyzed for soils with different compositions, and the thermo-mechanical properties of porous media with water and gas are studied by considering the soil water retention curve (SWRC). Different methods, i.e. volumetric average method, self-consistent method, Hashin-Strikman method, are employed to calculate thermal conductivity coefficients, and a new method is proposed to determine the thermo-mechanical parameters. Comparison of the results obtained by different methods shows that the proposed method is in a good agreement with the experimental results and is suitable for describing the main properties of the thermomechanical behaviors of soils. The relationship between the SWRC and the seepage curve is further studied by the natural proportional rule. The characteristics of the SWRC, its differential coefficient and the seepage curve, are investigated by considering the physico-mechanical mechanism; the limit scopes of the indices of the SWRC and the seepage curve are also given.