Journal of Cold Regions Engineering

In permafrost valleys, artesian wells often penetrate highly pressurized aquifers beneath confining subpermafrost. These wells must be quickly brought under control at installation, and heated through their operational life to prevent them from freezing in winter. However, water breakthrough of the permafrost barrier around the casing results in loss of control of the well. Seepage icing impacts to property and infrastructure can be catastrophic, and the costs to regain well control and mitigate damages high. Methods to regain control of artesian wells in permafrost are few and risky. A new method, cryogenic freezeback, was successfully used to mitigate an uncontrolled artesian well in a permafrost valley north of Fairbanks, Alaska. This paper documents the freezeback method, seepage and thermal analyses, and well abandonment and retrofit. Thermal monitoring results are presented to demonstrate the long-term effectiveness of the method.

This paper focuses on the development of simplified mathematical models of the cryosphere which may be useful in further understanding possible global climate change impacts and in further assessing future impacts captured by global circulation models (GCMs). The mathematical models developed by leveraging the dominating effects of freezing and thawing within the cryosphere to simplify the relevant heat transport equations are tractable to direct solution or numerical modeling. In this paper, the heat forcing function is assumed to be a linear transformation of temperature (assumed to be represented by proxy realizations). The output from the governing mathematical model is total ice volume of the cryosphere. The basic mathematical model provides information as a systems modeling approach that includes sufficient detail to explain ice volume given the estimation of the heat forcing function. A comparison between modeling results in the estimation of ice volume versus ice volume estimates developed from use of proxy data are shown in the demonstration problems presented.

The writers have derived a unified governing equation for freezing saturated soils. This equation considers the governing mechanisms with respect to individual thermal and hydraulic fields. The writers included coupling effects such as the thermodynamic equilibrium on the water-ice interface. The morphology of the solid matrix and the physical chemistry of the water-ice interface have also been incorporated. The equation is comprised of terms with clear physical meanings. Typical properties that are indicative of freezing soils, e.g., segregation potential, can be derived from this equation. The writers discuss the material properties that are required for implementation of the equation. For the conventional parameters in the equation, i.e., thermal conductivity, heat capacity, and hydraulic conductivity, the corresponding mathematical descriptions were investigated. The functions for prediction of these parameters during the soil freezing process are presented. The writers have also proposed a relationship between the temperature and unfrozen water content for characterization of freezing saturated soils. The writers propose that the measurement of this relationship be conducted with a new technique that uses a thermo–time domain reflectometry (TDR) sensor. The writers have described detailed sensor and experiment designs for measuring this new relationship and have compared the results with data that were measured with a standard method.