Prediction of long-term cooling effect of thermal pipe foundation of transmission tower in permafrost regions considering the change of thermal pipe power
(1. School of Civil Engineering，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China；2. Key Laboratory of Road and
Bridge and Underground Engineering of Gansu Province，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China)
Abstract：For power transmission towers along Qinghai—Tibet railway line which rans across permafrost regions，the biggest problem is to solve the long-term thermal stability of transmission tower pile foundation. In order to study the long-term cooling effect of thermal pipes applied to the pile foundation of transmission towers，a three-dimensional finite element analysis model of thermal pipe foundation was established based on frozen soil heat transfer theory and field test of thermal pipe foundation of power tower in the Wonkhu—Budongquan section of Qinghai—Tibet railway and considering global warming，frozen soil phase change，hydration heat release of concrete and change of thermal pipe power factors，et al. The power of thermal pipes and the temperature of the pile-soil system in 50 years were calculated and analyzed. The calculation results show that，in the first two years，the calculated and measured values are in good agreement with each other，which indicates that the proposed model can reasonably simulate the dynamic change of the temperature of the pile-soil system in this site. Within 30 years of the whole life cycle of the thermal pipe，the power of the thermal pipe decreases in a discontinuous wave form. The thermal pile foundation can effectively increase the cold reserve of the foundation and reduce the soil temperature. In the fifth year，the soil temperature around the pile is the lowest and the melting depth is the least. The thermal pile foundation can increase the permafrost upper table by 48 cm in the thirtieth year. In order to maintain the thermal stability of the transmission tower foundation，it is recommended that thermal pipes are replaced by new ones or that other engineering measures are adopted in the second year after the end of the life of the thermal pipes.
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2019, Vol. 38 
