摘要
介绍低应变反射波法检测基桩完整性原理,通过对青藏铁路基桩质量检测,发现在高原冻土环境下,基桩的质量问题主要是扩颈。产生桩身扩颈的原因是:施工期进入6月以后,气温相对升高,冻土层在机械施工扰动下,破坏了原来冻土环境,造成冻土融化后形成扩孔。根据有关冻土资料表明,地基土的法向冻胀力取决于地基土的冻胀性,基础底板受法向冻胀力随基础埋深的增加而减小;切向冻胀力在桩身缺陷处,会产生应力集中,使桩身破坏。对于扩颈桩,由于扩颈处桩周侧面积增大而使切向冻胀力增大对桩产生不利影响。针对冻土区冻胀力对基桩的危害,提出了改善基桩施工质量的措施。
This paper introduces the test integrity rationale of the low strain reflection wave method. Through the quality test of QinghaiTibet Railway piles, it is found that expanding neck is the main problem of the pile quality under the environment of permafrost plateau. The cause that leads to the expanding neck is that the weather becomes warmer after June and the frost stratum is disturbed by movement of the construction machineries. The original permafrost environment is damaged. After the thawing process, there forms the expanded hole. According to frost soil data, the normal frostheaving stress depends on the frostheaving property of the foundation soil. The normal stress decreases with the increase of the depth of foundation. The tangent frost heaving stress will generate stress concentration at the pile defects, thus damaging the pile body. As for the pile with the expanding neck, the tangent stress grows due to the increased area around the pile′s side, which is detrimental to the pile body. Due to the threat of the frostheaving stress in the frost region against the pile, the paper suggests the measures for the improvement of the quality of the piles.
出处
《中国铁道科学》
EI
CAS
CSCD
北大核心
2003年第5期40-43,共4页
China Railway Science
关键词
青藏铁路
基桩检测
反射波法
应用分析
Qinghai-Tibet Railway
Pile test
Reflection wave method
Application and analysis
