Abstract
In recent studies, vapour transfer is reported to lead to remarkable frost heave in unsaturated soils, but how to better model this process has not been answered. In order to avoid the great uncertainty caused by the phase change term of vapour‐water‐ice in the numerical iteration process, a new numerical model is developed based on the coupled thermal and hydrological processes. The new model avoids using the local equilibrium assumption and the hydraulic relations that accounts for liquid water flow, which provides a new way for the water‐heat coupling movement problem. The model is established by using COMSOL Multiphysics, which is a multiphysics simulation software through finite element analysis. The model is evaluated by comparing simulated results with data from column freezing experiments for unsaturated coarse‐grained soils. Simulated values of the total water content compare well with experimental values. The model is proved to be applicable and numerically stable for a high‐speed railway subgrade involving simultaneous heat and moisture transport. An agreement can be found between the predicted and measured frost/thawed depth and soil moisture profiles, demonstrating that the model is able to simulate rapidly changing boundary conditions and nonlinear water content profiles in the soil.
Highlights
Many engineering problems, including cracking of pavements, damage to the foundation of structures, and fracture of pipelines, are caused by the freezing and thawing process in cold regions. [1,2,3]
Severe frost heave problems were reported to occur at an airport in Northwestern China with 20 m-deep groundwater table and limited annual rainfall. e specific phenomenon was named as the canopy effect by Zhang et al [9]. e researchers attributed the water accumulation beneath the impervious cover to the vapour transfer in unsaturated freezing soils
Aiming to better understand the mechanism of vapour flow and phase change in unsaturated freezing soils, this study presents a theoretical framework to formulate the coupled thermal and hydrological process
Summary
Many engineering problems, including cracking of pavements, damage to the foundation of structures, and fracture of pipelines, are caused by the freezing and thawing process in cold regions. [1,2,3]. It is shown that vapour transfer can result in ice accumulation in unsaturated freezing soil and, cause frost damage to infrastructures. Considering that more evidence has revealed the complexity in soil freezing process, a large number of sophisticated models or parameterizations have been presented during the following several decades [13,14,15,16,17] Some of these studies take the contribution of vapour flow and its Advances in Civil Engineering phase change into account, while others choose to neglect yet. Aiming to better understand the mechanism of vapour flow and phase change in unsaturated freezing soils, this study presents a theoretical framework to formulate the coupled thermal and hydrological process. Some conclusions are drawn based on the results and discussion
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