In Situ Experimental and Numerical Analyses on Thermal Stability of Ordinary Embankment of Qinghai-Tibet Railway in Beiluhe Basin

Ordinary embankment was applied for some part of sections along Qinghai-Tibet Railway in permafrost regions, but thermal stability of the embankment is closely related to the operation of the railway. During the year of 2002~2003, an experimental section of ordinary embankment was constructed for monitoring the thermal regime. Based on the temperature data measured in situ, temperature variation of slope surface, temperature distribution beneath the embankment, and heat flux into the permafrost were analyzed. The results showed that the difference of heat transfer between the south and north slopes was very obvious, the mean annual temperature of south slope was 2.9°C higher than that of north one, and the annual range of temperature of north slope was 2.2 °C higher than that of south one. Attributing to the temperature boundary condition at the surface of embankment, the thawing depth of the embankment beneath the south slope was deeper than that beneath the north one, and the thermal regime of soil beneath the embankment was in an increase state. The heat budget indicated that the soil was in the absorbing heat state year after year, though the absorbing rate was decreasing. The thermal boundary condition was fitted by the temperature dada measured in situ. The temperature distribution is simulated under the assumption that the air temperature will warm up 1.0°C in 50 years by using the finite element software. The simulated results shows that the permafrost table would decline remarkably and ground temperature would rise markedly after 50 years.