Study on the relationship between the shallow ground temperature of embankment and solar radiation in permafrost regions on Qinghai–Tibet Plateau

The temperature field of permafrost embankments is a key factor to determine the embankment stability. On the basis of observed climate data and field-temperature values in Beiluhe on the Qinghai–Tibet Plateau, this paper uses statistics methods to set up a regression equation between the temperature at shallow ground depth (0.5 m) and the net radiation on embankment horizontal surface. There is a good linear relation between the temperature and the net radiation after the phase difference is removed. Moreover, an empirical formula consisting of the shallow-ground temperature of (0.5 m) and the direct solar radiation is proposed. It is also suitable for the area having high elevation at the Beiluhe site. These formulas combining with the law of documents and materials suggest that there exists an obvious linear relation between the temperature on horizontal surface and the direct solar radiation. However, there is hardly linear relation between the temperature and the direct solar radiation on embankment slopes. The key factor is that the railway embankment slope has a relatively heavier gradient. The slopes with heavier gradient have different heat transfer characteristic during a specific year. In summer, the sun is shining straight on the ground, which results in a relatively lower direct solar radiation on slopes; however, because of diffuse radiation and higher temperatures of the horizontal surface, temperatures on slopes are relatively higher. In winter, the direct solar radiation on shady slopes is even zero, meaning that there is almost no direct solar radiation. Thus, the relations between the temperature and the direct solar radiation on slopes are more complicated.

► We monitored the temperature.
► We monitored the net radiation.
► We study on the relationship between temperature and solar radiation.
► There is a linear relation on horizontal surface.
► There is hardly linear relation on embankment slopes.