摘要
对于冻土工程而言, 基础热稳定性是决定工程稳定性及服役性能的关键. 为预测±400 kV青藏直流联网工程多年冻土区砼灌注桩基础的长期热稳定性, 建立了考虑相变问题的二维数值传热分析模型, 应用有限元方法研究了气候变暖背景下, 不同年平均地温、不同含冰量条件下灌注桩基础传热特性和长期热稳定性. 结果表明： 单桩对周围土体的热影响范围是桩径的4~5倍, 桩基周围融化深度随时间推移而增大, 在低含冰量的高温和低温冻土区桩基50 a后最大融化深度分别为6.65 m和3.05 m, 所对应的冻土上限平均融化速率分别为9.5 cm·a-1和3.6 cm·a-1;在高含冰量的高温和低温冻土区50 a后最大融化深度分别为5.25 m和2.77 m, 其冻土上限平均融化速率分别为6.7 cm·a-1和2.0 cm·a-1. 在气候变暖背景下, 桩基上部周围冻土逐渐升温、融化, 50 a后, 在低含冰量的高温冻土区桩基由于融化深度增大导致有效冻结长度减少28%, 在高含冰量的高温冻土区桩基的有效冻结长度减少15%, 桩侧冻结力随之相应减小. 该研究对于冻土区桩基长度设计、桩基工程的维护和冻土稳定性评价提供了重要的科学依据.
In permafrost regions, foundation stability and work performance is depended on thermal stability of the foundation. In this paper, finite element method is used and a 2-D numerical analysis model is established to research heat transfer characteristics and to predict long-term thermal stability of cast-in-place piles in permafrost regions, which belong to the 400 kV Qinghai-Tibet Electric Transmission Line, with different mean annual ground temperatures （MAGTs） and ice contents within permafrost and in consideration of climate warming. The results show that a range of 4-5 times radius of the pile will be disturbed thermally, and the thaw depth around the pile foundation will be increasing as time goes on, the maximum thawed depths in a warm and ice-poor permafrost area and in an ice-poor permafrost area with low temperature are 6.65 m and 3.05 m, respectively, after 50 years;the thawing rate of the permafrost table reaches 9.5 cm·a-1 and 3.6 cm·a-1, respectively, in warm and low temperature permafrost areas;the maximum thawing depth in warm permafrost areas and low temperature ice-rich permafrost areas is 5.25 m and 2.77 m, respectively, 50 years later;the thawing rate of the permafrost table in warm and low temperature permafrost areas reaches 6.7 cm·a-1 and 2.0 cm·a-1, respectively;frozen ground around the pile foundation is warming and thawing due to climate warming. The effective adfreezing lengths of piles in warm, ice-poor and warm, ice-rich permafrost areas reduce by 28% and 15%, respectively. The adfreezing force around the foundation is decreasing. This study provides a very important scientific base for pile design, maintenance and estimate of stability in cold regions.
出处
《冰川冻土》
CSCD
北大核心
2013年第5期1209-1218,共10页
Journal of Glaciology and Geocryology
基金
国家重点基础研究发展计划(973计划)项目(2012CB026106)
国家电网公司科技项目(SGJSJS(2010)935-936)
国家自然科学基金创新群体项目(41121061)
中国科学院西部之光项目资助
关键词
青藏直流
灌注桩
数值模拟
热稳定性
多年冻土
Qinghai-Tibet DC Electric Transmission Line cast-in-place piles numerical simulation thermal stability permafrost
