Finite element analysis of heat and mass transfer in unsaturated freezing soils: Formulation and verification

Most subsurface unsaturated soils at high latitudes experience the freeze–thaw cycles annually. The temperature change and water redistribution of the active layer lead to the degradation of the soil strength, resulting in a series of geological and engineering problems. An improved thermo–hydraulic (TH) coupled model for unsaturated freezing soils in cold regions is proposed and the corresponding computer code is developed based on the finite element method. Some physically-based models such as the soil freezing characteristic curve and the freezing point depression are taken into account in this model. Compared with the published results of horizontal and vertical freezing experiments, the reliability of the proposed model and developed computer code are verified. In addition, the variation rules of unfrozen water content and total water content during the freezing process are analysed and then some important conclusions are drawn. The TH coupled model in this work can provide a basis for further study on geotechnical engineering and geological problems in cold regions.