Regulating solar absorptance for remedying thermal asymmetry of a roadway embankment

Abstract

Roadways in permafrost regions are laid upon embankments because permafrost stratum is highly sensitive to the thermal disturbance at the ground surface. The south-facing slope of the embankment is exposed to longer insolation than the north-facing one annually, differing the solar absorption of the side slopes and thus developing differential settlement across the embankment. A simple, economical strategy is to reduce the solar absorptance of the southern side slope to a critical level such that the solar absorption of both slopes is equalized. However, it is unknown this critical absorptance of a specific embankment and it is also unknown if this critical absorptance can be achieved by using existing techniques. This study mimics the solar radiation falling on the side slopes of embankments with different configurations, and subsequently it estimates the solar absorption of the side slopes. We found that in sunny weather when the thermal asymmetry of an embankment is maximum, reducing the southern side-slope absorptance from 0.80 to 0.40 can eliminate the thermal asymmetry. By analyzing the solar absorptance of a rough surface such as a crushed-rock layer, we can ascertain that this critical absorptance can be achieved by coating the side slope with nonwhite high-reflective pigment.