Cooling mechanism of embankment with block stone interlayer in Qinghai-Tibet railway

In order to study the cooling mechanism of embankment with block stone interlayer under open and closed conditions, an experimental railway section was built and data within one freeze-thaw cycle were collected. The results explain well the cooling mechanism of embankment with block stone interlayer. Under the open condition in cold seasons, the enforced convection effect occurs within block stone interlayer when the wind speed is large; however, the weak air convection occurs within the block stone interlayer near the bottom of the embankment when the wind speed is slow. Under the open condition in warm seasons, heat conduction occurs within block stone interlayer due to the change in wind speed and direction. Under I he closed condition, however, the enforced convection within block stone interlayer is so weak that heat conduction is dominant in the whole year because wind is blocked. Therefore, the cooling effect of embankment with a block stone interlayer to the soil beneath it is produced by enforced convection and weak free air convection; both its process and the cooling intensity are controlled by the local wind speed and direction. Because of the difference in the cooling effects, the soil temperature beneath the embankment has a temperature difference of 21 degrees C 41 degrees C between the open and closed conditions.