The thaw bulb produced by a heated pipeline buried in a stream channel may intercept water confined in shallow unfrozen zones beneath a seasonally frozen layer. Resulting movement of ground water through the thaw bulb might produce quick conditions in the pipeline foundation materials. A digital model showed that such conditions are not likely to occur. Test drilling along the proposed route of the pipeline confirms this conclusion. An exception may be the situation in which the pipeline is buried in fine sand overlying a highly permeable coarse sand or gravel.
The results of model studies demonstrate that the heated trench will focus ground-water discharge near the pipeline, especially in winter. Such discharge will increase the number and size of icings.
Explosive icing mounds apparently result from high crystallization pressures that develop within a closed talik. The thaw bulb close to the buried pipeline relieves the pressure that leads to such conditions.
Potential problems related to thaw-bulb enlargement by heat convection and thaw-instability of fine-grained materials are not treated in this analysis.
