Modelling frost heave in unsaturated coarse-grained soils

Coarse-grained soils were considered not susceptible to frost heave. However, substantial frost heave has been observed in unsaturated coarse fills in high-speed railway embankments. Recent experimental results in the literature show that vapour transfer has a considerable influence on the frost heaving of coarse-grained soil. However, vapour transfer has rarely been considered in modelling frost heave. This study presents a new frost heave model that considers vapour transfer and its contribution to ice formation. An updated computer program (PCHeave) is developed to account for the vapour transfer in unsaturated coarse-grained soils, where the rigid ice theory is applied to initiate ice lens formation in the frozen fringe. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The frost heave data monitored in 2013-2014 along the embankment of the Harbin-Dalian Passenger Dedicated Railway are also used to validate the proposed model. The prediction of the model agrees well with the measured results of frost heave and frost depth. This indicates that the proposed model can reasonably reflect the process of frost heave caused by vapour transfer in unsaturated coarse-grained soils.