Ice lens growth process involving coupled moisture and heat transfer during freezing of saturated soil

A model is developed to describe one-dimensional growth process of ice lens during freezing of saturated soil. Main factors controlling thickness and movement of unfrozen liquid film in frozen soil are analyzed by use of the thermodynamic theory for the liquid layer near a substratum. Water movement in the active zone is dealt with as Darcy flows controlled by a new concept called equivalent pressure, and a new model of coupled moisture and heat transfer is constructed based on it. The mechanism of ice lens growth process is studied, and the concurrence of uplifting effect caused by disjoining pressure and suction effect controlled by equivalent pressure during coupled process in active zone is indicated. The existence of frozen fringe is regarded as the indispensable condition for active lens growth in non-highly-colloidal soil with no pressure in supply water. Tests on continuous freezing and intermittent freezing are conducted for frost susceptive soil, and experimental results of final ice lens growth in both tests are used to testify the model and computation. The study shows that the calculated results are in agreement with the observation; and for the intermittent freezing, the disappearance of frozen fringe during the intermittent stage prevents the growth of final lens, thus the frost heave is partially controlled because of the deficient growth of final lens. Finally, problems about optimizing cold end temperature in order to control the frost heave are discussed.