基于热棒功率变化下多年冻土区输电塔热棒桩基的长期降温效果预测
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摘要
青藏铁路建设中输电塔穿越多年冻土地区,最大的难题是解决输电塔桩基的长期热稳定性问题。为研究热棒应用于输电塔桩基的长期降温效果,基于冻土传热学相关知识,考虑全球气候变暖、冻土相变、混凝土水化放热、热棒功率变化等因素,结合青藏铁路望昆—不冻泉段电力塔热棒桩基的现场试验,建立热棒桩基的三维有限元模型。计算分析50 a内热棒功率和桩土体系温度场。计算结果表明:最初2 a内的计算值与实测值吻合度较高,说明数值计算能较好的模拟此场地桩土体系温度的动态变化;在热棒的全寿命周期30 a内,热棒功率呈非连续波浪递减式变化;热棒桩基能有效增加冷储量,降低土体地温,第5年桩周土体地温降至最低,融化深度最小,第30年可提高冻土上限48cm;建议在热棒寿命结束后的第2年更换新的热棒或进行其他工程处理措施保持输电塔基础的热稳定。
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.
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.
引文
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[8]李永强.青藏铁路多年冻土区热棒直径对降温效果和产冷量的影响分析[J].岩土工程学报,2011,33(增1):510-515.(LI Yongqiang.Influences of diameter of thermal probes on effect of decreasing earth temperature and producing cold quantity along Qinghai-Tibet railway in permafrost area[J].Chinese Journal of Geotechnical Engineering,2011,33(Supp.1):510-515.(in Chinese))
[9]武俊杰,马巍,孙志忠,等.用估算热收支的方法评价热制冷效果[J].冰川冻土,2010,32(1):106-115.(WU Junjie,MA Wei,SUN Zhizhong,et al.Evaluating cooling effect of two-phase closed thermosyphon by estimated heat budget[J].Journal of Glaciology and Geocryology,2010,32(1):106-115.(in Chinese))
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[11]孙文,吴亚平,郭春香.热棒对多年冻土路基稳定性的影响[J].中国公路学报,2009,22(5):15-19.(SUN Wen,WU Yaping,GUOChunxiang.Influences of two-phase closed thermosyphon on permafrost roadbed stability[J].China Journal of Highway and Transport,2009,22(5):15-19.(in Chinese))
[12]中华人民共和国行业标准编写组.JGJ 118-2011冻土地区建筑地基基础设计规范[S].北京:中国建筑工业出版社,2011.(The Professional Standards Compilation Group of People?s Republic of China.JGJ118-2011 The designing criterion of the foundations in permafrost regions[S].Beijing:China Architecture and Building Press,2011.(in Chinese))
[13]郭春香,吴亚平.太阳辐射及气候变暖对冻土区单桩承载力的影响[J].岩石力学与工程学报,2014,33(增1):3 306-3 311.(GUOChunxiang,WU Yaping.Effects of solar radiation and global warming on bearing of single pile in permafrost region[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(Supp.1):3 306-3 311.(in Chinese))
[14]郭春香,杨凡杰,吴亚平,等.混凝土水化热对寒区隧道围岩融化及回冻过程的影响[J].铁道学报,2011,33(11):106-110.(GUOChunxiang,YANG Fanjie,WU Yaping,et al.Influences of concrete hydration heat on the melting and refreezing processes of surrounding rock of tunnels in the permafrost region[J].Journal of the China Railway Society,2011,33(11):106-110.(in Chinese))
[15]吴亚平,郭春香,赵世运,等.青藏高原冻土区灌注桩入模温度对地温场的影响分析[J].铁道学报,2004,26(6):81-85.(WU Yaping,GUO Chunxiang,ZHAO Shiyun,et al.Influence of casting temperature of single pile on temperature field of ground in permafrost of Qinghai-Tibet plateau[J].Journal of the China Railway Society,2004,26(6):81-85.(in Chinese))
[16]贾艳敏,田海旗,郭红雨.水化热及入模温度对灌注桩回冻过程影响的研究[J].工程力学,2011,28(1):44-47.(JIA Yanmin,TIANHaiqi,GUO Hongyu.Study on the influence of hydration heat and initial casting temperature on the refreezing process of bored pile[J].Engineering Mechanics,2011,28(1):44-47.(in Chinese))
[2]刘厚健,程东幸,俞祁浩,等.高海拔输电线路的冻土工程问题及对策研究[J].工程勘察,2009,(4):32-36.(LIU Houjian,CHENGDongxing,YU Qihao,et al.Study on frozen soil engineering problems and countermeasures of high altitude transmission lines[J].Geotechnical Investigation and Surveying,2009,(4):32-36.(in Chinese))
[3]潘卫东,连逢愈,邓宏艳,等.寒区工程中热棒技术的应用原理和前景[J].岩石力学与工程学报,2003,22(增2):2 673-2 676.(PANWeidong,LIAN Fengyu,DENG Hongyan,et al.Application principle and prospect of thermal-probe technique in cold region engineering[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(Supp.2):2 673-2 676.(in Chinese))
[4]SMITH L B,GRAHAM J P,NIXON J F,et al.Thermal analysis of force air and thermosyphon cooling system for the inuvik airport expansion[J].Canadian Geotechnical Journal,1991,28:399-409.
[5]李永强.热棒在青藏高原风火山地区的实测效果分析[J].岩石力学与工程学报,2003,22(增2):2 669-2 672.(LI Yongqiang.Analysis of the actual measurement result of the thermal probes in Fenghuoshan area on Qinghai-Tibet plateau[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(Supp.2),2 669-2 672.(in Chinese))
[6]蒋代军,王旭,刘德仁,等.青藏铁路多年冻土地基输电塔热棒桩基稳定性试验研究[J].岩石力学与工程学报,2014,33(增2):4 258-4 263.(JIANG Daijun,WANG Xu,LIU Deren,et al.Experimental study on stability of thermal pile foundation of transmission tower in permafrost foundation of Qinghai-Tibet railway[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(Supp.2):4 258-4 263.(in Chinese))
[7]郭春香,吴亚平,董晟,等.热棒填土路基降温效果的三维非线性有限元分析[J].中南大学学报,2014,45(增1):202-207.(GUOChunxiang,WU Yaping,DONG Sheng,et al.Three-dimensional nonlinear finite element analysis of cooling effect of thermal pipe embankment[J].Journal of Central South University,2014,45(Supp.1):202-207.(in Chinese))
[8]李永强.青藏铁路多年冻土区热棒直径对降温效果和产冷量的影响分析[J].岩土工程学报,2011,33(增1):510-515.(LI Yongqiang.Influences of diameter of thermal probes on effect of decreasing earth temperature and producing cold quantity along Qinghai-Tibet railway in permafrost area[J].Chinese Journal of Geotechnical Engineering,2011,33(Supp.1):510-515.(in Chinese))
[9]武俊杰,马巍,孙志忠,等.用估算热收支的方法评价热制冷效果[J].冰川冻土,2010,32(1):106-115.(WU Junjie,MA Wei,SUN Zhizhong,et al.Evaluating cooling effect of two-phase closed thermosyphon by estimated heat budget[J].Journal of Glaciology and Geocryology,2010,32(1):106-115.(in Chinese))
[10]汪双杰.高原多年冻土区公路路基稳定及预测技术研究[博士学位论文][D].南京:东南大学,2005.(WANG Shuangjie.Research on highway subgrade stability and prediction technology in plateau permafrost regions[Ph.D.Thesis][D].Nanjing:Southeast University,2005.(in Chinese))
[11]孙文,吴亚平,郭春香.热棒对多年冻土路基稳定性的影响[J].中国公路学报,2009,22(5):15-19.(SUN Wen,WU Yaping,GUOChunxiang.Influences of two-phase closed thermosyphon on permafrost roadbed stability[J].China Journal of Highway and Transport,2009,22(5):15-19.(in Chinese))
[12]中华人民共和国行业标准编写组.JGJ 118-2011冻土地区建筑地基基础设计规范[S].北京:中国建筑工业出版社,2011.(The Professional Standards Compilation Group of People?s Republic of China.JGJ118-2011 The designing criterion of the foundations in permafrost regions[S].Beijing:China Architecture and Building Press,2011.(in Chinese))
[13]郭春香,吴亚平.太阳辐射及气候变暖对冻土区单桩承载力的影响[J].岩石力学与工程学报,2014,33(增1):3 306-3 311.(GUOChunxiang,WU Yaping.Effects of solar radiation and global warming on bearing of single pile in permafrost region[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(Supp.1):3 306-3 311.(in Chinese))
[14]郭春香,杨凡杰,吴亚平,等.混凝土水化热对寒区隧道围岩融化及回冻过程的影响[J].铁道学报,2011,33(11):106-110.(GUOChunxiang,YANG Fanjie,WU Yaping,et al.Influences of concrete hydration heat on the melting and refreezing processes of surrounding rock of tunnels in the permafrost region[J].Journal of the China Railway Society,2011,33(11):106-110.(in Chinese))
[15]吴亚平,郭春香,赵世运,等.青藏高原冻土区灌注桩入模温度对地温场的影响分析[J].铁道学报,2004,26(6):81-85.(WU Yaping,GUO Chunxiang,ZHAO Shiyun,et al.Influence of casting temperature of single pile on temperature field of ground in permafrost of Qinghai-Tibet plateau[J].Journal of the China Railway Society,2004,26(6):81-85.(in Chinese))
[16]贾艳敏,田海旗,郭红雨.水化热及入模温度对灌注桩回冻过程影响的研究[J].工程力学,2011,28(1):44-47.(JIA Yanmin,TIANHaiqi,GUO Hongyu.Study on the influence of hydration heat and initial casting temperature on the refreezing process of bored pile[J].Engineering Mechanics,2011,28(1):44-47.(in Chinese))