Risk Evaluation of Frost Jacking for Tower Foundations along Qinghai-Tibetan Transmission Line and Anti-Heave Measures

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research Pub Date : 2012-11-09 DOI:10.1061/9780784412473.057

Z. Wen, Qihao Yu, Dayan Wang, Guo-yu Li, Jianming Zhang

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引用次数: 7

Abstract

The Qinghai-Tibetan ±400 kV direct current grid interconnection project runs across 1038 km of permafrost and seasonally frozen-ground in the interior of the Qinghai-Tibetan Plateau. The mean annual air temperature of the Qinghai-Tibetan Plateau varies between -3 ℃ and -7 and the minimum air temperature ℃ is lower than -37 in short durations. The active ℃ layer is subjected to annual freeze-thaw cycle and its thickness varies between 2 m and 3 m. significant heave force is expected due to the existence of extensive frost susceptible soils and cold weather. The tower foundations tend to be jacked out of the ground and result in expensive maintenance costs and foundation failure, which significantly threatens the safety and normal operation of the transmission line. Therefore, it becomes the first concern to prevent the frost jacking failure for design and construction of the Qinghai-Tibetan transmission line. To protect the transmission system from damage, it is necessary to evaluate the engineering risk and to employ some effective countermeasures to mitigate the frost-related damages. To evaluate the risk and provide reasonable suggestions for design and construction, a safety coefficient calculation which involves with the frost penetration, frost heave force, freezing strength as well as loads is conducted. The results show that the spread-type footing has more excellent performance to resist uplift loads than drilled shaft. To improve the safety of foundations, anti- heave measures including non-frost susceptive soil backfill, bevel foundation design, surface treatment and two-phase closed thermosyphon, etc were proposed and applied in the construction of the Qinghai-Tibetan grid project. The advantages and applicability of anti-heave technical solutions are described.

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青藏输电线路塔基础冻顶风险评价及抗隆起措施

青藏±400千伏直流并网工程穿越青藏高原内部1038公里的多年冻土和季节性冻土。青藏高原年平均气温在-3 ~ -7℃之间，短时间最低气温低于-37℃。活动℃层受年度冻融循环影响，其厚度在2 ~ 3 m之间变化，由于存在大面积的霜感土壤和寒冷天气，预计会产生较大的升力。塔架基础容易被顶出地面，造成维护费用昂贵和基础破坏，严重威胁输电线路的安全与正常运行。因此，防止顶霜失效成为青藏输电线路设计和施工的首要问题。为了保护输电系统不受冻害，有必要对工程风险进行评估，并采取有效的措施来减轻冻害。为了评估风险，为设计和施工提供合理的建议，进行了涉及冻侵力、冻胀力、冻结强度和荷载的安全系数计算。结果表明，摊开式基础比钻孔式立井具有更优良的抗拔荷载性能。为提高地基的安全性，提出了抗冻土回填、斜角地基设计、地表处理、两相封闭式热虹吸等抗隆起措施，并在青藏电网工程施工中予以应用。介绍了抗胀技术方案的优点和适用性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Accounts of Chemical Research 化学-化学综合

CiteScore

31.40

自引率

1.10%

发文量

312

审稿时长

2 months

期刊介绍： Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance. Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.