| dc.description.abstract | The starting point of this work is a conceptual model for frost heave based on nonequilibrium thermodynamics. According to the theory, the temperature gradient in the soil under frozen condition is the main driving force for transport of water from the warmer (unfrozen or less frozen) soil towards the colder, partly frozen, soil volume. The tendency of water flow results in increase of pore water pressure close to the freezing front, which means a reduction in the effective stress. An ice lens can start to form after a crack appears. However, freezing front may continue moving forward, and the formation of active ice lens will stop when soil permeability behind freezing front dramatically decreases. According to the conceptual model, a new fully coupled THM model is developed. The mass balance equation, energy balance equation and momentum balance equation are presented herein. In order to consider ice lenses, Extended Finite Element Method (X-FEM) is employed to solve the governing equations. The primary variables of the governing equations, i.e., displacement, water pressure and temperature are approximated according to the properties of discontinuities with shifted Heaviside function and modified level-set function. The calculated results are compared with the available results of three lab scale onedimensional freezing tests on Devon silt. These tests include one freezing test without overburden pressure and two freezing tests with different overburden pressure of 100 kPa and 45 kPa, and reasonable agreement is achieved.
Shut-off pressures is also estimated, and the results are as expected from the coupled transport equations. | en_US |
