Frost heave in coarse-grained soils: experimental evidence and numerical modelling

Frost heave in coarse-grained soils caused by vapour transfer has attracted much attention, but little experimental or numerical evidence has been reported thus far. A series of laboratory experiments is carried out by a frost heave apparatus and an X-ray micro-computed tomography instrument. The only water supply mechanism to the tested specimen is vapour transfer. The results indicate that considerable frost heave occurs in coarse-grained soil specimens with a zero fines content. The ratio of frost heave to the initial height can reach 13·8% and 25·1% at 14 days and 18 days, respectively. Ice crystals first grow in pores causing the soil particle to rotate and move, and the soil porosity to increase. With continued ice crystal growth, they eventually become connected and form an ice lens. If a constant temperature gradient is applied, only one horizontal ice lens is formed, which differs from the layered ice lenses observed in fine-graded soils. A new numerical model is developed to simulate ice formation and frost heave in coarse-grained soils, which considers the process of vapour transfer and desublimation. The predicted frost heave results agree well with the measured results. This study provides a novel explanation for the frost heave mechanism in coarse-grained soils.