Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway
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This paper investigates the stability of the earthen roadbed built in the warm and ice-rich permafrost region. The varying thermal regime of the subgrade and the ongoing settlement of the roadbed were observed at field. The temperature data demonstrate that in warm and ice-rich permafrost regions, adoption of earthen roadbed results in warming of the underlying permafrost. It is primarily because the earthen roadbed traps the warm-season absorbed heat in the natural ground. In addition, the carried heat of the earthen roadbed that was constructed in warm season propagates downward to warm the underlying soil. The warming permafrost layer promotes the roadbed settlement, which was mostly linearly developed in the past five service years. A comprehensive analysis for the varying thermal regime and the ongoing settlement shows that the unfrozen water liberated from the warming, undrained layer experiences consolidation. The deformation of the undrained soils is mainly responsible for settlement of the roadbed. In comparison, the temperature variation of this warming permafrost layer is found to be less beneath roadbeds protected by thermosyphons or crushed rock revetments. The installation of thermosyphons into the earthen roadbed is recommended to prevent the further degradation of the underlying permafrost.
KeywordsPermafrost warming Unfrozen water Climatic warming Thermosyphon Ice-rich permafrost Consolidation undrained
This research was supported by the National Natural Science Foundation of China (NSFC No. 40730736). Supported by Fund of the State Key Laboratory of Frozen Soils Engineering (Grant Nos. SKLFSE-ZQ-02 and SKLFSE-ZY-03), and China Postdoctoral Science Foundation (Nos. 200902312 and 20080430110). The authors are indebted to Dr. LaMoreaux and two anonymous referees for their thorough, meticulous English edit across the manuscript.
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