The Dry Creek Highway Section is located along the Alaska Highway in the Yukon Territory of Canada. The site was identified as a key highway section that required foundation stabilization due to degrading, warm (>-0.5°C) ice-rich permafrost and massive ground ice in excess of 9 m thick. Thermal design for permafrost stabilization incorporated sloped thermosyphons installed beneath the existing highway embankment to passively cool the permafrost foundation.
The design specified 58 thermosyphon installed every 7 m on center beneath the existing highway embankment, with evaporator pipes 34 m in length that were installed in a cased borehole at an ~11° incline beneath the embankment. The inclined boreholes were drilled from the embankment toe to limit the need for excavation and to maintain integrity of the existing embankment, allowing for unimpeded use of the vital cross-border transportation route between Alaska and the Yukon Territory. Numerical thermal modeling was used to verify performance of the design and optimize thermosyphon radiator size and evaporator pipe distance in the ground to reduce project cost and ensure long-term performance with consideration of climate change.
This presentation will cover the thermal design and initial performance over the first two years since construction. Ground temperature measured at two monitoring sections have confirmed initial cooling of the foundation by several degrees Celsius in response to thermosyphon heat extraction from the foundation. The most notable change in ground temperature from the baseline period occurs beneath the centerline where the embankment thickness is the greatest. At some sideslope positions, the permafrost table has begun to aggrade upward into thaw-stable material. The Dry Creek Permafrost Stabilization project contributes to evaluation of sloped thermosyphons for adaptation of surface infrastructure to address climate change in permafrost environments.
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