Freezing Curves of Ottawa Sand with Varying Organic Matter and Salinity

This study focuses on the investigation of the soil freezing behavior of sand having peat and pore fluid salinity under freeze–thaw conditions. The motivation is to address the limited empirical data available for coarse-grained soils with organic and saline inclusions, which are common in permafrost environments. In this research, a series of laboratory experiments were performed using Ottawa sand prepared with varying initial saturation, peat content, and NaCl concentration, while a constant dry density was kept constant. Capacitance sensors were used to measure and monitor volumetric water content and temperature during a single freeze–thaw cycle. Results from the experiments indicate that both salinity and peat affect the unfrozen water content at temperatures below 0°C by depressing the freezing point and retaining bound water and changing the shape and slope of soil freezing curves. The findings from these experiments will be useful for the refinement of dielectric models for better prediction of soil freezing curves. In addition to that, the findings will improve the representation of heterogeneous sand containing organic matter and salinity for permafrost modeling.