An experimental study of the relationship between the matric potential, unfrozen water, and segregated ice of saturated freezing soil

Frost heave damage is caused by the in situ freezing of pore water and segregated ice due to moisture migration. Previous studies have shown that in freezing soil, moisture migration is related to the pore water pressure gradient, and moisture migration is the dominant reason for the formation of an ice lens. However, the essential relationship between ice segregation and the matric potential is still controversial. Using a pF meter sensor, a 5TM volume water content sensor, and a digital image capture system, the relationship between the matric potential and the unfrozen water in saturated freezing soil was monitored in real time, and digital images of the formation of segregated ice were collected. Furthermore, the time space coupling relationships between the unfrozen water, the matric potential, the frost-heaving amount, the moisture migration, and the formation of an ice lens were systematically analyzed during soil freezing. The results demonstrate that there is an internal relationship between the moisture migration driven by the matric potential (from the micro-perspective) and the segregated ice layer effect (from the macroscopic perspective). In addition, the unfrozen water and the matric potential in the frozen area have a significant impact on the distribution of the segregated ice lenses.