Laboratory Assessment of a New Road Permafrost Mitigation Technique: The Half Pipe Cover

摘要

The snow/sun shed is a proven mitigation technique effective in stopping progressive permafrost thawing beneath embankment side-slopes. However, safety concerns and high-construction expenses have prevented the widespread use of snow/sun sheds for embankment protection. To find a better low-cost deployable system that still uses the same cooling principles than the snow/sun shed, a new mitigation technique was tested at Laval University. A series of half pipes were applied on a small-scale embankment slope in a cold room set at -20°C. The temperatures measured in the embankment slope at 0.22 m below the soil surface are: 1) -5.2°C lower compared to the reference embankment when the half-pipes extremities were left open to air circulation; 2) -4.6°C lower when the inlets of the half-pipes were sealed with mineral wool (to simulate snow clogging); 3) -4.2°C when both extremities were sealed with mineral wool. In terms of heat fluxes, the three configurations of half pipe cover tested were between 1.7 to 1.8 times more effective at extracting heat than the reference embankment. Finally, implementing this mitigation technique on the slopes of a road embankment has the potential to induce a significant cooling of soil temperatures.