Study on Thermal Balance of Asphalt Pavement and Roadbed Stability in Permafrost Regions of the Qinghai-Tibetan Highway

WANG Shao-ling, ZHAO Lin, LI Shu-xun, JI Guo-liang, XIE Ying-qin, GUO Dong-xin (Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou Gansu 730000, China)  

For thoroughly understanding the failure mechanisms of the road in permafrost regions of the Qinghai-TibetanHighway, radiation and thermal balance were observed on the surface of asphalt pavement and two ground surfaces ofdifferent types of permafrost between the Kunlun Pass and Maintenance Squad No. 66(MS-66). Thermal balance of different permafrost sectionsbelow asphalt pavement and annual thermal cycle of the roadbed were calculated based on the observation. There is a part of heat transferredinto the roadbed. Although it only occupies 2%～3% ofthe thermal balance of the road surface, this part of heat has significant influence on the heat regime of the roadbed. This is the main reason responsible for the formation of a thawed core below the roadbed and for the failure of the roadbed in high-temperature permafrost section. Ratio of the total heat absorption to the total heat releasing over the road surface is 1.19∶1for the road surface at the Kunlun Pass, and 4.0∶1 at the MS-66. This means that the heat income and loss below the roadbed is approximately balanced, temperature of permafrost is low and stable, and no thawed core will be formed below the roadbed in the near future at the Kunlun Pass. The heat absorption of the road surface is 4 time of the heat loss at the MS-66. Thawed core began to form 3 years after laying the asphalt pavement, and then gradually thickened. According to a calculation concerning the formation of thawed core below a roadbed, a thawed core will increase during the first ten years with a mean rate of 26 to 27 cm per year. Then the increasing rate will gradually decrease during the second and third ten years, with a decreasing rate very slow since the 40th years. After 30 years the thawed depth will be varying between 6 and 8 m, about 70% of the maximum thaweddepth. After 2010 AC the ice content below the artificial upper limit of the roadbed will gradually decrease, thawing settlement will be small and the roadbed will become to a quasi-stable state. In order to decrease the downward heat transfer from the surface, attempts should be made to change the road surface color, structure and material to decrease and offset a part of heat transferred into roadbed.

【Key Words】： Qinghai-TibetanHighway asphalt pavement radiation and heat balance roadbed stability
【Fund】： 国家重点基础研究规划项目! (G19980 40 80 0 );; 中国科学院重点基金项目! (KZ95 2 S1 2 15 )
【CateGory Index】： U419.92

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