Freezing and thawing of soils is a multiphysics process that involves heat transfer, moisture flow and deformation with potential development of cracks and disintegrations. Understanding these phenomena is key for the formulation of physically realistic models that can be used to describe natural phenomena and engineering applications. The research presented in this thesis aims to advance the understanding and modelling capability of coupled thermo-hydro-mechanical (THM) processes involved in soil freezing and thawing. In this work, a non-local approach based on Peridynamics theory (PD) is presented for coupled THM model for freezing and thawing of soil. A PD model for the description of the coupled thermo-hydraulic (TH) process of freezing and thawing saturated soils is first established and verified. The model is then established to analyze unsaturated soils, reliably representing the processes of water and heat transfer under conditions of freezing and thawing. The model is further extended to THM formulation by incorporating a new form of linear momentum conservation equation that accounts for volume expansion during freezing. This approach allows us to reliably predict the formation of ice lenses and the associated development of soil frost heave. Additionally, to expand the model application range, it is demonstrated how to account for the presence of polar and axial symmetries in the considered soil domain, as well as how the model's numerical parameters can affect the accuracy of the solution. The agreements between model predictions and experimental data, as well as with the results of analytical models and other numerical approaches (where applicable) under different geological and technological conditions, suggest that the newly developed non-local theoretical and computational framework for the analysis of soil freezing and thawing can be effectively utilized in scientific analysis and engineering design. The model is applied to study the artificial ground freezing under TH conditions. It is shown that accounting for the rapid changes in soil properties during phase change can ensure a more accurate prediction of the ice wall delivery under conditions of high-velocity groundwater flow. The developments presented in this thesis advance the fundamental understanding of physical processes in freezing and thawing of soils and provide a basis for improved design and implementation of artificial ground freezing. Additionally, the developed model can be applied for the analysis of a broad range of coupled THM problems that are presented in other various engineering applications involving phase changes in evolving porous media.
Multiphysics modelling of soil behaviour during freezing and thawing
Nikolaev, P. (Author). 31 Dec 2024
Student thesis: Phd