Identifying ice lens initiation of frozen soils using particle image velocimetry method

Frost heave occurring in embankments seriously threatens the safe operation of transportation infrastructures in cold regions. When and where the ice lens initiates are key to understanding the mechanism of frost heave in soils. This study develops a novel particle image velocimetry technology specifically suited for a frost heave apparatus. The displacement, velocity, and strain of the three-dimensional frost heave surface are acquired with this technology, and the monitoring accuracy reaches the micron level. A series of one-dimensional freezing tests are carried out for silt soil to validate the applicability of this novel technology. The validation of the test results confirms the effectiveness of the method. The results indicate that the measured displacement and velocity induced by the initiation of ice lenses can clearly depict the development of the frost heave process. Ice lens initiation can be identified where peaks of strain values occur during the freezing stage. The proposed criterion, based on image velocimetry measurements, thus provides a new tool for assessing the formation of ice lenses during frost heave process.