Thermal characteristics and declining permafrost table beneath three cooling embankments in warm permafrost regions

This article analyses the long-term thermal stability of the newly constructed Gonghe-Yushu Expressway (GYE) embankments with special structures in the warm permafrost regions of the south-eastern Tibetan plateau to ensure driving comfort and safety. Using field monitoring and numerical calculation methods, the ground temperature distribution characteristics, changes in the artificial permafrost table (APT), and the heat budget around the permafrost tables of three types of embankments (insulated board embankment [IBE], crushed rock embankment [CRE] and ventilated embankment [VE]) are studied. The results indicate the following: 1) each embankment plays a positive role in cooling the underlying permafrost in cold seasons but melts the underlying permafrost during warm seasons, 2) the ground temperature effect is increased in the shallow and deep layers on the shoulders of each embankment, 3) the heat budget around the permafrost table of each embankment is characterized by the absorption of heat, and the IBE has the greatest heat absorption capacity; and 4) calculations have determined that the APT of each embankment declines linearly over time, and a model is developed to calculate permafrost table change established for each embankment. The model may provide reference for predicting the service year and declining extent of APT of expressway embankments in warm permafrost regions.