Long-term evaluations of insulated road in the Qinghai-Tibetan plateau

In order to protect permafrost from further thawing due to human activities, thermal insulation treatment might be the first choice for embankment design in permafrost regions. In 1992, a test roadbed with insulation was built at Kunlun mountains along the Qinghai-Tibetan highway. An insulated and an uninsulated testing section, the later serves as a comparison, were constructed and instrumented in 1995, to evaluate the effect of Extruded polystyrenes (EPS). Ground temperature observations in the recent 8-year period showed that the insulation in embankment worked properly and it may decrease the annual range of ground temperature greatly. We find that there is hardly any change in the thermal conductivity of EPS in 10 years after the embankment construction, which means that environmental factors such as vehicle loading, moisture content, freezing–thawing action, etc. have little effect on the insulation. In addition, the mean temperature rise rate of permafrost underlying the embankment with insulation is smaller than that of permafrost underlying the embankment without insulation over 7 years. Heat budget calculation showed that the heat exchange may decline enormously due to the application of insulation in embankment. Moreover, the insulation method may decrease three quarters of the heat entering into embankments compared with common embankment. Using a finite element method, we analyze the situations, which are suitable for application of the insulation method along Qinghai-Tibetan highway and, furthermore, how to use it.