The purpose of this study is to develop numerical models and tools to simulate the processes of freezing and thawing in soils and to predict frost heave associated with freezing of frost-susceptible soils.; A numerical procedure for heat transfer in freezing and thawing soils is presented first. The frozen soil is a mixture of solid particles, unfrozen water, ice, and air. The multi-phase nature and the unique role of pore water complicate the heat transfer process in freezing or thawing soils. A major characteristic of the pore water is its presence in frozen soil even at temperatures well below freezing. As a result, the latent heat of fusion of water is released or absorbed over a range of temperatures below freezing, rather than at one particular temperature. This effect as well as the variation of thermal properties of the soil mixture has been taken into account in the heat transfer model. In addition, the hysteretic nature of unfrozen water content in frozen soil was considered for the first time in the heat transfer analysis in freezing and thawing soils. One-dimensional and two-dimensional examples are presented to show the capability of this numerical procedure.; The major part of this dissertation is focused on the modeling and simulation of frost heave. The porosity rate model described in this dissertation is based on the description of the global response of the soil to freezing. Formation of individual ice lenses is not modeled; instead, a porosity rate function is proposed to determine the porosity increase caused by the ice growth. This growth depends on the temperature, the temperature gradient, and the stress state. The model was first calibrated and then validated using experimental data. The effectiveness of this model is illustrated in an example of freezing of a vertical cut in a frost-susceptible soil. A more complex problem of freezing of a retaining wall system demonstrates the potential usage of the model in engineering practice to improve design and prevent frost damage.
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