A model for predicting the hydraulic conductivity of warm saturated frozen soil

Buildings built in the permafrost regions are always subjected to frost heave and thawing settlement deformation, which is mainly attributed to changes in foundation soil properties with environmental temperature, especially the hydraulic conductivity of warm frozen soil. To investigate the influence of the temperature on hydraulic conductivity, this study presented a model for predicting the hydraulic conductivity of warm frozen soil. Based on the discontinuous noncircular capillary bundle model, the expression of the hydraulic conductivity of the unsaturated soil was derived with the modified Hagen- Poiseuille equation, the Kelvin equation, the Campbell model for the matric potential and the Darcy's law. Then, based on the assumption that water transport in saturated frozen soil behaves with the same process as that in unsaturated unfrozen soil, the hydraulic conductivity model for warm frozen soil was proposed. To assess the predictive power of the proposed model, the predicted and tested hydraulic conductivities of eight different sets of soil were compared. The comparison results suggest that the proposed model performs well for the tested data. The results suggest that the hydraulic conductivity of warm frozen soil is mainly determined by the unfrozen water content, which is controlled by the temperature and soil particle size distribution. The proposed model is simple in the mathematical formula and readily integrated into frost heave and thawing settlement models. In addition, the model shows the relationship of hydraulic conductivity between saturated frozen soil and unsaturated unfrozen soil. •A hydraulic conductivity model for warm saturated frozen soil is proposed.•Hydraulic conductivity of frozen soil is mainly determined by unfrozen water content.•The pore size distribution method is recommended to determine the air entry values.•Hydraulic conductivity of frozen soil can be estimated by that of unfrozen soil with same water content.