The ADOT Jim River Maintenance Building, located over permafrost in central Alaska, has experienced significant floor heave following startup in late 1986 of an active subgrade cooling system (SCS), even though foundation soils appear to remain frozen year round. After constructing a new floor in mid-1987, cumulative floor heave by 1990 ranged from about 1-5 inches (25-127 mm). However, the annual heave rate has been decreasing as the mean frozen ground temperature progressively cools.

Published unfrozen moisture, hydraulic conductivity, and thermal induced heave relationships were used to reasonably model the recorded floor heave and rates. At Jim River, 25-50% of the heave recorded since mid-1987 may be associated with redistribution of unfrozen water under influence of thermal gradients established during operation of the SCS. The results suggest this phenomenon should be considered for some SCS designs, especially over warm permafrost.

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