Field experiment study on effects of duct-ventilated railway embankment on protecting the underlying permafrost

Cooling principle is adopted in roadbed constructions in permafrost regions on the Qinghai–Tibet Plateau for protecting the underlying permafrost. One way is to use duct-ventilated embankment. Ground temperature data were collected along experimental embankments in Beiluhe section of the Qinghai–Tibet railway. Analyses of ground temperature changes and heat influx indicate that ventilation ducts effectively cool the soils surrounding the ducts in the embankment. Permafrost behavior beneath conventional embankment and test embankments with ducts installed at high and low positions was studied over 3 years. The permafrost under the conventional embankment and the duct at a high position in the embankment decreasingly absorbs heat during the period. The ground temperature of the permafrost under the conventional embankment rises and that under the duct at a high position embankment decreases slightly. The temperature of the permafrost under the duct at a low position decreased remarkably. These findings demonstrate that a ventilated embankment with a low position duct produces beneficial effects that actively cool the subgrade soils and keep the roadbed thermally stable. Accordingly, they were strongly recommended for use in the construction of embankments in the permafrost regions on the plateau.