Using Air Convection Ducts to Control Permafrost Degradation under Road Infrastructure: Beaver Creek Experimental Site, Yukon, Canada

Thermal degradation of permafrost under road infrastructure regularly results in thaw settlement and severe structural damages. The present study discusses the results obtained by the implementation of a mitigation technique at a test section along the Alaska Highway near the Alaska-Yukon border (Beaver Creek). The objective of this study was to test possible way to slow down or prevent permafrost degradation under road embankment. Longitudinal air convection duct is a heat exchanger device based on fluid mechanics allowing for extraction of heat from the embankment by natural convective heat transfers during winter. Thermal analysis of the air temperature inside the ducts indicated that there was a strong thermal gradient between the inlets and the outlets, with air temperatures being 6 to 10°C higher at the outlet than at in the inlet of the ducts. The cooling effect of the air convection duct system elevated the permafrost table by about 1 m over 3 years. This indicates that air convection ducts have a very good potential for heat extraction within road embankment and the underlying permafrost. This technique will likely find rapid applications in the engineering community aiming to develop adaptation strategies to climate warming for road infrastructure.