Constructing of the Qinghai-Tibet Railroad Using the Principle of Cooling the Roadbed
More than half of the total length of the Qinghai-Tibet Railroad (QTR) traverses warm (0 to-1 ℃) permafrost areas, and about 40% of its total length is in ice-rich permafrost areas. The construction of the QTR also must consider the impacts of climatic warming along the QTR during the next 50～100 years. The latest projection indicates a warming of 2.2 to 2.6 ℃ on the Qinghai-Tibet Plateau (QTP) by the year 2050. Therefore, the key to the successful construction of the QTR is to protect permafrost from being thawed. Although railroad construction in permafrost areas has had a history of more than 100 years, the troubled sections of the railroads in permafrost areas have been greater than 30% of their total length. Based on the experiences and lessons learned from the road construction in permafrost areas, both in China and abroad, the author proposes that the principle of"active cooling"of railroad roadbed by lowering permafrost temperatures should be used in designing QTR, rather than that of"passive protection" of permafrost through increasing thermal resistance of roadway, such as increasing fill thickness and/or using insulative materials. This is especially important for the road sections in warm, ice-rich permafrost. In addition, this paper proposes several methods for"cooling the roadbed" by controlling radiation, convection and conduction through modifying roadway structure and using different fill materials.
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