Measuring ice lens initiation in soils by particle image velocimetry

Ice lens initiation is the core issue in understanding the dynamic process of frost heave. However, there are still limitations to find an adequate criterion for describing the formation of ice lens. A series of one-dimensional freezing tests is designed using the particle image velocimetry (PIV) method to monitor the frost heave and ice lens formation. The results show that the conventional parameters, such as displacement and velocity, cannot be used to track the ice lens formation, while the strain can be employed to detect the ice lens formation and investigate the freezing change patterns. This study proposes strain as a new criterion for assessing ice lens initiation, applicable across various soil types and freezing conditions (constant freezing and ramped freezing). The strain change in the region where the ice lens forms is the largest during the freezing process. Additionally, strain curves at the top of the soil samples can reveal different freezing patterns and distinguish the first and second frost heave stages. This newly developed technology enables continuous, non-destructive monitoring of ice lens initiation across diverse conditions and soil types, enhancing data visualization and three-dimensional modeling of freezing parameters while improving traditional methods by directly measuring velocity and strain in frost heave investigations. The study is expected to enhance the research of ice lens criterion and provide a new perspective for monitoring the freezing process.