Investigation of embankment with temperature-controlled ventilation along the Qinghai–Tibet Railway

The temperature-controlled ventilated embankment (TCVE) is an improved engineering measure developed based on the duct-ventilated embankment (DVE). The improved cooling effect of the TCVE is a result of enhanced heat exchange through controlling air convection in the ventilated ducts of the DVE. The field observational data from a TCVE testing section at Beiluhe, about midway in the Qinghai–Tibet Railway permafrost zone, indicates that restricting the air convection in the ducts during warm season can reduce the embankment heat absorption in the embankment. The results also indicate that the temperature in the wells of the ducts of the TCVE was about 1.0 °C lower than the temperature in the walls of the ducts of DVE. Especially it was found that in the seasonal ground temperature-decreasing period, the temperature of the permafrost at a depth of 3.5 m below the base of the embankment in TCVE decreased faster than at the same depth below the DVE. Two years after the TCVE was implemented, the temperature at a depth of 3.5 m below the embankment base was found 0.45 °C lower than at the same location below the DVE. Thermal modeling of the embankments shows that the mean annual heat loss of a TCVE is about twice that with the DVE, which means a doubled cooling effect of TCVE over DVE if think in this way. In addition, the cooling period with a TCVE is about 40 days longer than with a DVE, which contributes to its cooling effects.