Influence of freeze-thaw cycles on microstructure and hydraulic conductivity of saline intact loess

In this paper, influence of freeze-thaw (F-T) cycles on the microstructure and hydraulic conductivity were investigated on saline intact loess specimens by infiltrating sodium sulfate. X-Ray computed micro tomography (Micro-CT), and triaxial permeability tests were carried out to understand the relationship between the soil microstructure and hydraulic conductivity. The CT scan images suggest tiny holes in the soil structure expand to form cracks due to F-T cycles; these cracks were more pronounced in specimens with higher salt contents. The soil morphology was reconstructed using three-dimensional (3D) reconstruction technology, which highlights the significant influence of salt weathering on the microstructure of saline intact loess. Triaxial permeability test results suggest that the void ratio and hydraulic conductivity of saline intact loess both increase after F-T cycles or at higher sodium sulfate contents, which are consistent with the changes of the porosity of the 3D reconstructed model. Finally, an empirical relationship between hydraulic conductivity and void ratio was proposed incorporating the influence of F-T cycles and salt content. There is a good comparison between the calculated and measured data that establishes the rationality and validity of the proposed equation.