Characteristics of Unfrozen Water Content in Frozen Soils and Its Effect on Flexural Strength

Abstract

Unfrozen water content (UWC), which affects the mechanical behavior of frozen soil, was investigated over a continuous temperature range using an isothermal adiabatic calorimeter. The employed soil materials were fine sand, clay and a mixture of fine sand and clay. Water, with or without NaCl, was added to the soil materials. Specimens were obtained by freezing the saturated soils rapidly. The UWC increased with salt concentration and content of fine soil particles. A temperature rise increased the UWC in all frozen soils. A rapid increase in UWC was observed around the eutectic point of saline frozen sand. However, the rapid increase was not observed for saline frozen clay. Total UWC was divided into UWC in brine and absorbed UWC. It was found that the UWC in brine decreases with the content of fine soil particles. Then, the flexural strength of frozen soils was examined for various characteristics of UWC. The dependence of flexural strength on salt concentration was agreement with the dependence on UWC in brine, and the dependence of flexural strength on the content of fine soil particles was in agreement with the dependence on absorbed UWC. The flexural strength of frozen soils, including those containing both salt and fine soil particles, was not determined by the total UWC, but predominantly by UWC in brine.