EXPERIMENTAL INVESTIGATION OF AIR CONVECTION EMBANKMENTS FOR PERMAFROST-RESISTANT ROADWAY DESIGN

Abstract

Air convection embankments have been proposed as a method for avoiding thaw-settlement of roadways in regions of warm permafrost. These embankments are constructed of poorly-graded open aggregate, resulting in a very high air permeability. Unstable air density gradients that develop within the embankment during winter result in buoyancy-induced pore air convection. This convection increases the heat flux out of the embankment and foundation material during winter months. During summer, the air density gradient is stable and convection does not occur. The net effect is an increase in winter cooling without a corresponding increase in summer warming and thawing is prevented in the permafrost layer beneath the embankment. The present study discusses thermal data collected from an experimental air convection embankment that was constructed at BrownOs Hill Quarry near Fairbanks, Alaska and monitored over a two-year period. The results show a large cooling influence due to air convection within the embankment during winter.