Application of PIV Technique in Model Test of Frost Heave of Unsaturated Soil

Frost heave of soil is a highly nonuniform problem, in which the local deformation is much more severe and meaningful compared with the overall deformation. When soil is upon freezing, a water–ice phase change occurs and induces the migration of pore water. Subsequently, the distribution of temperature, water content, ice content, and fabric is highly nonuniform in frozen soil. The local frost deformation of soil mainly depends on the local temperature, soil water content, and ice content. In this study, the particle image velocimetry (PIV) method is introduced into the soil column test to monitor the local frost deformation. Several tracer particles are tested to overcome the difficulty that the deformation field is not clear in clay soil. The results demonstrate that the mixed sand is a suitable choice of tracer particles and can lead to clear contours of vertical displacement and strain. Such local deformation information is valuable and can be synthetically analyzed with the local temperature, soil water content, and ice content. The PIV technique is considered to be a good choice for monitoring the local frost deformation field in frozen soil.