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《Journal of Glaciolgy and Geocryology》 2002-02
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Assessment Model of Permafrost Thermal Stability under Engineering Activity

WU Qing-bai\+\{1, 2\},\ ZHU Yuan-lin\+1,\ LIU Yong-zhi\+1 (1. State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China; 2. AECI, Department of Earth Science, Nanjing University, Nanjing Jiangsu 210093, China)  
In this paper a model of thermal stability is put forward, which is expressed by ratio \%Q\%\-t/ \%Q\%\-+, where \%Q\%\-t is the total heat of thawing sediment from the bottom of seasonal thawing layer to the potential seasonal freezing depth and the heat spent in temperature rising to 0 ℃ of the bottom seasonal freezing layer, and \%Q\%\-+ is the absorbed heat in the warm season. Based on the monitor data of frozen soil along the Qinghai-Tibetan Highway, the thermal stability model is used to analyze the relationships among thermal stability, mean annual ground temperature, permafrost table temperature and seasonal thawing depth. \ \ Analysis results show that thermal stability can well reflect the change of frozen soil under natural state and human activity. Thermal stability has a close relationship with mean annual ground temperature, temperature at the bottom of seasonal thawing layer, and seasonal thawing depth. Permafrost thermal stability linearly changes with permafrost table temperature and mean annual ground temperature Thermal stability increases with mean annual ground temperature decreasing. The higher the MAGT is, the smaller the ratio \%Q\%\-t/ \%Q\%\-+ is. Permafrost is easy changing with environmental factors. The relationship between permafrost thermal stability and seasonally thawing depth is an exponential one. When permafrost thermal stability is stronger, the absorbed heat in warm season can only result in slight thawing in the sediments from the bottom of the active layer to the potential seasonally freezing depth, and is unable to raise the temperature at the bottom of the active layer to 0 ℃. With permafrost thermal stability weakening, the absorbed heat in warm season can result in greatly thawing in the sediments from the bottom of the active layer and the potential seasonally freezing depth, and is able to raise the temperature at the bottom of the active layer to 0 ℃. \ \ According to the classification of permafrost stability, permafrost table change and thermal regime along the Qinghai-Tibetan Highway, permafrost can be divided into four types: thermal stable permafrost, transitional thermal stable permafrost, thermal unstable permafrost and extreme thermal unstable permafrost. Thermal stability reflects the change of comprehensive factors of frozen soil and sensitively responds to the change of environmental factors under human activities.
【Fund】: 中国科学院知识创新工程重大项目 (KZCX -SW -0 4) ;; 国家自然科学基金重大项目 ( 90 10 2 0 0 6 ) ;; 中国科学院寒区旱区环境与 工程研究所创新项目 (CACX2 10 0 47;CACX2 10 0 86 ) ;; 南京大学博士后基金资助
【CateGory Index】: P642.14
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