In-situ testing study on convection and temperaturecharacteristics of a new crushed-rock slopeembankment design in a permafrost region

For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment designcombined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section ofthe Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics.The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especiallyin cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new designof the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of theconvection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushedrock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a bettercooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditionalcrushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annualtemperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat fluxcalculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated thatthe new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful inproviding some references for improved engineering design and maintenance of roadbeds in permafrost regions.