LAUSR

Abstract Separate embankment is an important subgrade structure in the future Qinghai-Tibet expressway (QTE) construction. In this work, the comprehensive earth-atmosphere coupled heat transfer numerical model of the 26 m width embankment and the different spacing separate embankment had been built. To make the analysis more general, 12 typical computation cases which consider the distribution pattern of upper soil type and external environment conditions along the QTE have been developed. In the computation, the spatial and temporal temperature distribution characteristics of 26 m width embankment and the separate embankment under the given working condition are calculated and compared. Then heat transfer characteristic, freeze-thaw feature, and reasonable interval of separate embankment are investigated. The computation results show that: compared with the prominent heat absorption and heat collection effect of the 26 m width embankment, the separate embankment contributes greatly to reducing the subgrade thermal disturbance and protecting the underlying permafrost, thus the separate embankment should be a reasonable choice for the future Qinghai-Tibet expressway. The maximum thaw depth and thaw plate are influenced by parameters such as ambient temperature and water content of frozen soil. The increase of subgrade interval also reduces the influence of subgrade on underlying permafrost and the maximum thaw depth. And above decreasing trend becomes negligible when the interval of separate embankment reaches to a certain value, therefore there is an optimal spacing between the permafrost subgrade on the heat transfer perspective.