Theoretical Investigation into Thermo-Osmosis and Thermofiltration Effects on Hydromechanical Behavior of Saturated Soils

A change in temperature induces thermo-osmosis (T-O) and thermofiltration (T-F) effects in soils, which can influence consolidation under certain conditions. Whether such conditions are met is not always known a priori. Therefore, this paper first develops a coupled model to assess these effects on the thermohydromechanical coupled behavior of saturated soils. The proposed model, which incorporates the extended Darcy’s law and Fourier’s law, is implemented in the finite-element method (FEM) solver OpenGeoSys version 6.3.3. To determine when T-O/T-F effects become relevant in an analysis, two characteristic numbers are then derived from the extended governing equations, which can be directly expressed by readily available soil and water parameters. Both theoretical and numerical analyses were conducted, and the results indicate that the T-F effect has little influence on heat transfer in typical soils, while the T-O effect appears to be significant for both sandy and clayey soils, provided the T-O coefficient exceeds $4.3\times {10}^{-12}{\mathrm{m}}^2/(\mathrm{s}·\mathrm{K})$. The T-O effect could even lead to the development of negative excess pore water pressure (PWP) and, consequently, soil compression, with relevance for the stability of geotechnical facilities subjected to temperature gradients. It is thus inferred that the T-O coefficient should be measured in conjunction with related necessary experimental work, in addition to soil permeability, to determine whether the T-O effect should be treated with caution.