摘要
针对青藏直流联网工程塔基热稳定性问题,建立空气-热管-土体耦合传热数学模型,并利用该模型开展锥柱式基础传热过程及热管冷却降温效果的模拟预测研究.结果表明:冷季热管工作期间,其周围地温梯度明显较大且呈"纺锤形"分布.同时,由于锥柱式基础及其底座为热的良导体,热管产生的冷量通过锥柱式基础及其底座快速向基础底部传递,使得基础下部形成大范围低温冻土,这对主要考虑融沉病害的锥柱式基础而言十分有利.暖季热管停止工作期间,浅层地温主要受环境温度影响,锥柱式基础附近融化深度大于天然地表下,二者差值约35 cm.通过热管剖面及无热管作用中间剖面地温对比,发现单一塔腿在4根热管措施作用下,锥柱式基础周围多年冻土地温分布较为均匀,可避免冻土地基的显著不均匀沉降变形.热管周围土体快速降温过程主要集中在前5 a,之后受气候变暖影响桩基础及天然地表以下上限深度不断增加,多年冻土地温缓慢升高.50 a气温升高2.6℃背景下,锥柱式基础下部多年冻土仍保持冻结状态,能够满足青藏直流联网工程对于冻土地基热稳定性要求.
For studying thermal stability of tower footing along the Qinghai-Tibet DC Interconnection Project, a coupled heat transfer model among air, thermosyphon and soil is established. Based on the model, heat transfer processes around the cone-cylinder pipe and cooling effects of the thermosyphon are simulated by finite element method. Results from the numerical simulation indicate that in cold seasons as thermosyphon works, ground tem- peratures around the thermosyphon have great gradients and distribute as a spindle, which reveals a remarkable cooling effect of thermosyphon. Meanwhile, cold energy from thermosyphon flows quickly to base of cone-cyl- inder pipe as high thermal conductivity of the concrete pipe. As a consequence, extensive cold permafrost devel- ops beneath the pipe, which is good for cone-cylinder pipe. In warm season, thermosyphon does not work and shallow ground temperatures are determined by air temperature. Also since high thermal conductivity of the pipe, the maximum seasonal thawing depth near pipe is obviously greater than that beneath original ground with a difference about 35 cm. Ground temperature around the pipe is uniform between profiles with and without ther- mosyphon. Quickly cooling processes of ground temperature near the pipe occur mainly within the first 5 years after application of the thermosyphon. And then, depth of permafrost table and permafrost temperatures increase slowly as air temperature increase. Overall, under the scenario of climate warming, soil beneath cone-cylinder pipe still keeps frozen, which meet the need of the project.
出处
《冰川冻土》
CSCD
北大核心
2014年第1期106-117,共12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)
中国科学院"西部博士"项目(51Y351211)资助
关键词
冻土地基
热管
传热过程
冷却降温
数值模拟
permafrost foundation
thermosyphon
heat transfer
cooling effect
numerical simulation
