Water and Environmental Research Center
Seminars
25 September 2009
Control of Permafrost Degradation Under Road Infrastructures – Overview of Beaver Creek (Yukon) Experimental Road Site Project
Eva Stephani
Credit: Amy Tidwell
Alaska Highway near Beaver Creek, site of the Experimental Road Site Project
Abstract
The Alaska Highway, a widely used transportation link, is severely affected by permafrost degradation. The road built in ice-rich permafrost areas has disturbed the natural ground thermal regime and caused the ground ice to melt. It has resulted in extended damages induced to the road which are only temporarily solved with annual maintenance works. Taking into account the high maintenance costs and the expected near future exacerbation of permafrost degradation with climate warming, the Yukon Highways and Public Works (YHPW) division has considered developing long term solutions. In collaboration with Alaska University Transportation Center, University of Montreal and Laval University, YHPW has implemented an experimental road site at Beaver Creek (Yukon) in 2008 to evaluate the efficiency of 11 mitigation techniques to control permafrost degradation along the Alaska Highway.
The methods tested explore the effect of enhanced winter air convection, albedo and insulation via various media. The techniques were designed to take advantage of the local micro-climatic summer and winter conditions (e.g. solar radiation regime, winter dominant winds, cold season temperatures, snow regime).
Prior to construction of the 500m long road experimental section, drilling and coring operations were conducted to confirm the presence of thaw-sensitive ice-rich permafrost. Based on an integrative geomorphological engineering approach, we conducted a detailed characterization of the permafrost including the cryostratigraphy, the ground thermal regime, the climatic conditions, and the geotechnical properties. A cryostructure classification has been developed to describe the ground ice content and type of all permafrost cores retrieved during the coring and drilling operations.
Three main cryostratigraphic units comprising very ice-rich syngenetic permafrost in alluvial silt deposits, ice-rich epigenetic permafrost in till and inactive to weekly active ice wedges network were identified, and characterized. Widespread deep talik zones were detected under the road. Thaw strain tests performed on permafrost cores resulted in substantial thaw-strain values. Ground thermal regime analysis showed that the active layer depth is considerably deeper under the road and in its vicinity than in the farther adjacent natural ground. At the centerline and in the road slopes, the active layer is now located below the road embankment.
The detailed characterization of the permafrost conditions will be integrated in a 3D GIS model to support future studies assessing the mechanical and thermal response of the mitigation techniques tested for the upcoming 15 years.
We present here an overview of the Beaver Creek road experimental site project.