Abstract
The bearing capacity and deformation characteristics of a tower foundation are seriously affected by its temperature status in permafrost regions. It is very important to maintain the tower foundation at a lower temperature status. In this paper, a ventilation duct is introduced into the tower foundation to decline the temperature around the tower footing. A 3D numerical heat transfer model is established to investigate the cooling effectiveness of a duct-ventilated tower foundation. Several cases with different parameters (e.g., diameters and buried depths) are calculated to compare the temperature distribution around the tower foundation during the cold season. The results show a significant cooling effect of the foundation near the ventilation duct, and an optimized case is found. In the warm season, the adjustable shutter is employed in the duct-ventilated tower foundation to prevent heat in the tower foundation. It is established that an adjustable shutter installed in the ventilation duct can keep the tower foundation in a frozen state in the warm season.
Highlights
Introduction e construction of the QinghaiTibet Power Transmission Line (QTPTL), running from Golmud (Qinghai Province) to Lhasa (Tibet Autonomous regions), began in July 2010 and was completed in October 2011
Since temperature is an important influencing factor, keeping a lower temperature is the key to guaranteeing the thermal stability of the tower foundation
In the late 1960s, thermosyphons were adopted to improve the thermal stability of foundations in the cold regions of Canada and America. ermosyphons have been used in the Qinghai-Tibet Highway in China since 1989 and have made an outstanding contribution. e cooling mechanism of thermosyphons [5, 6], the distribution of thermosyphons, the temperature distribution of the foundation [2, 7], the long-term cooling effect, and the stress of the thermosyphons were researched around the QinghaiTibet Power Transmission Line (QTPTL) [3, 8]
Summary
Where Cs and λs are the effective volumetric heat capacity and effective thermal conductivity, respectively. e phase change of the media in the tower foundation occurs in a range of temperatures (Tm ± ΔT). Where Cs and λs are the effective volumetric heat capacity and effective thermal conductivity, respectively. E phase change of the media in the tower foundation occurs in a range of temperatures (Tm ± ΔT). Csf and λsf are volumetric heat capacity and thermal conductivity of the media in the frozen area, respectively. Csu and λsu are volumetric heat capacity and thermal conductivity of the media in the unfrozen area, respectively. According to available research and the situ observations, the thermal boundary condition can be written as follows [32, 33]:. According to the investigation for wind in the Qinghai–Tibet Plateau, the wind velocity 10 m above the ground surface is changed based on the following equation [27]: Backfills
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