Characterizing Volumetric Changes and Cracking of Saline Soil under Freeze-Thaw Cycles

The freeze-thaw (F-T) behavior of saline soils is critical to transportation and geotechnical infrastructure in the regions subjected to seasonal changes and low-temperature conditions. This study conducts laboratory tests on clayey saline soil to investigate its surface morphology, volumetric evolution, and cracking behaviors under F-T cycles. Soils with different levels of NaCl concentrations [0M (Deionized Water), 1M, 2M, and 3M] are prepared and tested for Freeze-Thaw (F-T) and Wet-Freeze-Thaw-Dry (W-F-T-D) conditions. A high-resolution camera and 3D structured light scanner are placed above the samples to capture their 2D and 3D responses at the end of each cycle. Then the image processing techniques are used for 2D and 3D analysis. The results show that the water evaporation rates decrease with time and the water evaporation rate decreases with the increasing salt concentration due to the decrease in capillary potential and salt crystallization at the surface. Overall, the crack area, length, and fractal dimension decreased with increased NaCl concentration for F-T and W-F-T-D. The 2D analysis showed that crack area, crack length, and fractal dimension increased with cycle number for F-T cycles. The 3D analysis results showed that sample volume reduced over time, but the surface area and fractal dimension increased with continuous F-T cycles. The W-F-T-D samples showed that all the parameters were relatively closer to each other at individual salt concentrations except for the volume change. This can be attributed to the wetting and re-freezing, which bring the soil sample closer to the original intact soil sample.