Bidirectional convection mechanism and cooling performance of road embankment with a new duct-ventilated slope in permafrost regions

Embankment with duct-ventilated slope (EDVS) is a new kind of proactive roadbed cooling measure in permafrost regions, which is composed of multiple hollow cement ventilation ducts assembled side by side, and the ducts are laid down on embankment slope. To investigate its cooling mechanism and performance, a prototype field test was carried out on the Qinghai-Tibet Plateau. The in-situ flow visualization test revealed that EDVS can conduct the convection process of airflow upward parallel to the embankment slope at the windward slope and downward parallel to the slope at the leeward slope. Thus, the bidirectional airflow in the ducts is available, which is termed as “bidirectional convection mechanism” and first discovered in embankment slope cooling measures. The numerical simulation results indicated that the wind pressure gradient is the primary reason for the bidirectional convection mechanism. The bidirectional convection mechanism can effectively utilize the low-temperature air to reduce the subgrade temperature in cold seasons. The monitored data showed that EDVS reduced the annual average slope temperature by 3.8°C compared to the traditional no-covered embankment. EDVS provides new research for roadbed cooling measures in permafrost regions.