560 4TH CAN. PERMAFROST CONF. (1982) Thawing of permafrost by passive solar means

By pre-thawing and consolidating the upper layers of the permafrost, a thinner stable roadway embankment may be constructed, provided the thickness of the embankment plus that of the pre-thawed layers are adequate to contain the full seasonal thaw zone. Six test plots were established near Fairbanks, Alaska, in April 1980, to determine how surface modifications may be used to accelerate thawing of permafrost by increasing the solar heat gain. The various modifications examined included clearing and stripping the surface, construction of a thin gravel pad, darkening of the gravel pad surface with asphalt, and the use of clear polyethylene film to create a “greenhouse effect ” on both gravel pad and stripped sections. Each section simulated a full roadway width with adjacent uncleared vegetation. Instrumentation used to monitor performance included heat flow meters, windspeed and radiation sensors, and thermocouples for subsurface tem-perature observations. Thaw depths and surface settlements were recorded monthly at nine points on each section, and monthly measurements of surface albedo were also made for each treatment. Differences between thaw depths achieved with the different treatments have been as much as 40 per cent. Results of this study are used in analyses of probable benefits of roadways and airfields con-structed after pre-thawing for one season