Change in Ice Lens Formation for Saline and Non-Saline Devon Silt as a Function of Temperature and Pressure

During the freezing of a fine grained soil, ice lens formation changes the structure of the soil and results in frost heave. The formation of the ice lenses is very complex and dynamic. The results are presented from laboratory freezing tests on saturated Devon silt, a frost-susceptible soil. A variety of pore-water salinities, vertical pressures, and temperature gradients were used to investigate the different effects on the freezing process and the formation of the ice lenses. Using a novel experimental methodology, ice lens growth at the pore scale was observed. Fluorescein was dissolved in the pore water, which allowed to locate unfrozen water under UV light. In this manner it was possible to visually observe and measure the ice lens growth ahead of and behind the frozen fringe. It is visually shown that the thickness of the ice lenses, the distances between the ice lenses and the thickness of the frozen fringe change with changing temperature gradient, vertical pressure and salinity. In addition, the ice structure within the saline soils became more three dimensional and irregular compared to the non-saline samples, where the ice lenses develop over the entire cross section of the sample.