Sunny–shady slope effect on the thermal and deformation stability of the highway embankment in warm permafrost regions

The aim of this study was to investigate how the sunny–shady slope impacts on the thermal and deformation stability of the highway embankment in warm permafrost region. The investigation was done by analyzing both the observational geo-temperature and deformation data of the embankment in the experimental section K369+100 along the National Highway 214 on Qinghai–Tibet Plateau. Also, the fundamental cause of the embankment transverse asymmetrical thermal regime and asymmetrical deformation was discussed. The observation data indicates (1) for embankment in warm permafrost regions, the deformation stability is highly correlated with the thermal stability, and the embankment transverse deformation is mainly controlled by the ground temperature and its change; (2) the absorbed solar radiation difference between sunny and shady slopes results in the embankment's transverse thermal difference, which leads to asymmetrical deformation; and (3) the time of the highest settlement deformation does not coincide with that of the maximum thaw depth, which means that the development of the embankment deformation lags behind the development of embankment temperature. For the embankment with differential deformation in transverse section, the times of the highest settlement deformation on two sides of embankment are different. This difference lies in that the time of the highest settlement deformation on the sunny side is later than that on the shady side of the embankment. The differential deformation will be magnified over time, and finally the embankment stability is engulfed by the longitudinal cracks caused by asymmetric settlement of permafrost.