Modeling the thermal response of air convection embankment in permafrost regions

Permafrost degradation under transportation infrastructure often results in thaw settlement due to thawing of the ice-rich subgrade. Climate change is associated with permafrost-related engineering problems. Air convection embankments (ACE) have been proven to be an effective method to prevent permafrost thawing, in response to climate change. Poorly-graded aggregates are used to facilitate the air flow in an ACE, especially during winter when the air density gradient is unstable. A large-scale ACE test section was constructed along the Alaska Highway in 2008 at Beaver Creek, Yukon, Canada, to investigate the heat extraction capacity of ACEs. Boreholes under the toe, the side slope and the centerline were drilled and instrumented. Temperature data collected at this site were used to investigate the thermal performance of the ACE and to calibrate a 2D thermal model that was developed based on the Beaver Creek experimental site. Specific site characteristics, such as air temperature, foundation soil properties and embankment dimensions, were measured and used as input parameters to improve the accuracy of the 2D model developed. A relatively new approach based on heat balance at the embankment-soil interface has been proposed to investigate the heat extraction capacity of ACEs. After satisfactory calibration of the model at the Beaver Creek site, an engineering design chart has been developed and is proposed to assess the heat balance at the embankment-soil interface for different embankment thicknesses and site conditions.