The Alaska Highway is a vital cross-border transportation route connecting Canada and the USA. The impact of permafrost thaw has increased annual operating and maintenance costs which has prompted the Yukon Highways and Public Works (YHPW) and Transport Canada to evaluate the effectiveness of permafrost mitigation techniques to improve highway performance.
The Dry Creek Highway Section located along the Alaska Highway in the Yukon was identified as a key section of highway that required stabilization due to the presence of warm (>-1°C), ice-rich permafrost and massive ground ice over 9 m thick. SRK completed numerical thermal modeling of both an air convection embankment (ACE) and thermosyphon design. The model results showed ACE and thermosyphon designs were both expected to reduce permafrost thaw beneath the highway embankment. However, the thermosyphon design was shown to stabilize the degrading permafrost in a shorter amount of time.
The accepted design, based on a 30-year design life, incorporates sloped thermosyphons installed beneath the existing highway embankment to passively cool the underlying permafrost and massive ground ice. The thermal design criteria required that the maximum annual temperature at the top of the massive ground ice be maintained at or below -2°C for the warmest location between two thermosyphon evaporator pipes. Thermosyphon surface radiator size and evaporator pipe distance in the ground was optimized to reduce overall project cost and to ensure long-term performance over the design life with consideration of climate change. This presentation will discuss site conditions, permafrost stabilization options considered for project, and predicted performance of the accepted thermal design.
