Thermodynamic Model of the Ground Surface and EmbankmentSurface along the Qinghai-Tibet Railway (II):Results in the Cloud-Free Condition

Variations of frozen soil layer have direct relation with the energy exchange between the ground and atmosphere. The energy exchange contains three basic physical processes: radiation, convection and heat conduction. In this paper, a thermodynamics model of ground surface and embankment surface (RSTM) along the Qinghai-Tibet Railway constituted on the above physical processes is used, with observation from Amdo Station as the model input, aiming at the slope surface temperature changes and temperature differences between two slope surfaces on both sides of an embankment, which relate to the direction and gradient of the slope surface, to simulate the characteristics of the surface temperature of the embankment changing with direction and gradient of the slope under cloud-free condition. The results show that, for the embankment built on the spot in Amdo, the embankment top temperature is always higher than the air temperature and has a obvious high value in summer, despite a cooling effect on the slopes in any direction and gradients; In winter, although embankment top temperature is lower than 0 ℃, a strong heating effect on the southward slope causes the surface temperature increasing over the critical state of thawing frozen-in soil, and the opposite heating effect on different sides of the embankment via changing the freezing and thawing course can cause lengthways fissure on the embankment. Therefore, effective safety measure is necessary for the frozen soil embankment. A test by observation data shows that the RSTM has a good simulating performance and an important significance for forecasting the embankment heating status of the Qinghai-Tibet Railway.