Qinghai-tibet Plateau Of Embankment Temperature Field Research

As the permafrost has the trend of degradation because of the global climate wanning, the thermal stability of embankments in permafrost regions has received extensive attention.In this paper, many actual meteorological factors such as solar radiation, air temperature, wind velocity, wind direction and soil moisture evaporation were considered, and a new finite element method (FEM) to conclude them as the combination of the second and third boundary' conditions was put forward. Accordingly, FEM models of embankment thermal regime with phase change were set up, the transient thermal regime in embankments were numerically analyzed by FEM in different air temperature regions, with different embankment height, with different route strikes, with different types of pavements. The influence on embankment thermal regime and the permafrost temperature of embankment height, route strike, pavement types were analyzed in details. As a measure taken into use to protect the underneath permafrost, FEM were set up for the embankments with insulation under the first boundary condition. The influence on embankments thermal regime of insulation materials, insulation thickness, the insulation position and the construction seasons were analyzed in details.FEM analysis results show that, in year circulation, the embankment boundary temperatures vary as sinusoidal wave, in middle and low temperature permafrost regions, to raise the embankment height is beneficial to raise permafrost table and protect underneath permafrost, while in high temperature unstable permafrost regions, to raise the embankment height is liable for the instability of the embankment, the asymmetry of thermal regime is closely related to route strike and season variation, strongest in E-W strike embankment and the least in N-S strike embankment, and strongest in winter and the least in summer, the insulation embankments have different protection effectiveness and applicability in different permafrost stability regions, in -1C permafrost regions, insulation can display its effectiveness fully, insulation's optimal position is influenced by embankment height, permafrost annual mean temperature, construction season and etc, it should be placed in shallow position in low embankments, and in middle position in high embankments, it should be placed in shallow or middle position when constructed in cold seasons.