Abstract
The formation and layer of ice lenses during the freezing of soil in cold regions is closely related to frozen heave and moisture immigration. The purpose of the paper is to explain the physical mechanisms pertaining to ice lens formation, which were analyzed and verified using numerical simulation results. Based on a few assumptions, the formation and layers of ice lenses are illuminated in the following steps: the initial stage of freezing, formation of the first layer of ice lens, formation of the second layer of ice lens, and formation of the final layer of ice lens. Compared with the numerical results of coupled thermo–hydro–mechanical simulations of one-side freezing of soil columns in an open system, the proposed analysis method of the formation and layers of ice lenses is verified to be reasonable, and it is demonstrated that the classical criterion for the formation of ice lens in freezing saturated soil is only suitable for the final layer of ice lens. Finally, a new criterion, in terms of flux rate, for the formation of ice lens is proposed.
Highlights
Soil freezing in soil deposits near the ground surface may occur in response to seasonal variations of temperature
Frozen heave and ice segregation are crucial in geotechnical engineering in cold regions, as they can cause damage to pavements, displacement and fracture of oil pipelines, and loss of bearing capacity of structure foundation
In-situ and laboratory experiments have demonstrated that ice lenses are discontinuously distributed by layers and that thick ice lenses exist within the ground
Summary
Soil freezing in soil deposits near the ground surface may occur in response to seasonal variations of temperature. In-situ and laboratory experiments have demonstrated that ice lenses are discontinuously distributed by layers and that thick ice lenses exist within the ground To explain this phenomenon, the secondary frost theory has been proposed [3,4,5]. In the frozen fringe zone, the temperature of ice segregation, unfrozen water content, pore pressure, and hydraulic conductivity are key controlling parameters. Zhou and Meschke [16] proposed a three-phase finite element soil model based on poromechanics theory, in which solid particles, liquid water, and crystal ice are considered as separate phases, and mixture temperature, liquid pressure, and solid displacement as primary field variables. The existing criteria for the formation of ice lens in freezing soil render it challenging to analyze when and where ice lenses form before the formation of the final one; this issue was investigated in this study
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