Semianalytical Solution for One‐Dimensional Consolidation of Unsaturated–Saturated Soil Foundations Based on the Interfacial Flow Contact Resistance Model

ABSTRACT Based on the Hagen–Poiseuille law, a general imperfect flow contact model for a two‐layer soil system was constructed. In this model, the upper and lower layers are unsaturated and saturated soil, respectively. The laminar flow behavior, stemming from the low‐velocity flow of pore water along complex pore channels at the interface, was characterized by introducing the flow contact transfer coefficient () and flow partition coefficient (). The mechanical behaviors of unsaturated and saturated soils were described by Fredlund's unsaturated soil consolidation model and Terzaghi's saturated soil consolidation model, respectively. The semianalytical solution for the consolidation of unsaturated–saturated soil foundations was derived. This was achieved by applying the Laplace transform and the Crump inverse transform. The rationality of the model was validated through a comparative analysis of existing solutions. The research shows that the interface flow resistance effect significantly alters the distribution of pore water pressure. In the models considering interface flow resistance, relative pore water pressure gradients occur at interfaces. The gradient of pore water pressure at the interface in the general imperfect flow contact model is the most significant one among them. Moreover, the interface flow resistance effect reduces the settlement rate of the soil. Especially in the middle and later stages of settlement, the increase in the or the decrease in the has a more significant influence on the settlement in the process. Nevertheless, the final settlement amount is not influenced.