Thermal Status of the Main Roadbeds of the Qinghai-Tibet Railway in Permafrost Regions after 5 Years' Service

Overall, roadbeds of the Qinghai-Tibet Railway in permafrost regions have been stable since its operation in 2006. The train speed reaches 100 km/h, one of the designed requirements. The roadbeds were constructed under a principle of cooling-roadbed. The main adopted cooling-roadbed structures include the roadbed with crushed-rock basement embankment, the roadbed with the crushed-rock sloped embankment, and the roadbed with U-shape crushed-rock embankment. In some sections of the railway, the traditional roadbed was constructed in cold and ice-poor permafrost regions. In-situ monitored results indicated that the thermal stability of the traditional roadbed was marginal as evidenced by increasing ground temperatures. The roadbed with crushed-rock basement has resulted in an unsymmetrical thermal regime, although the ground temperature under it has been decreasing. The thermal status of the roadbed with the slopes covered with crushed-rock and the U-shape crushed-rock roadbed have performed much better than the former two. In the whole, the thermal stability of the cooling-roadbeds has been much better than the traditional roadbed.