为研究双排桩在南宁圆砾-泥岩组合地层中的支护特性,以南宁地铁4号线某深基坑工程为依托,运用ABAQUS有限元软件和现场监测数据进行分析,得出双排桩在该地层有较好适用性的结论。然后在此基础上,进一步探讨坑趾系数、深度比在影响阈值左右范围变化以及不同土体强度弱化百分比的工况下,坑中坑开挖对双排桩的影响。结果表明各因素对双排桩支护效果的影响强弱依次为土体强度弱化百分比、坑趾系数、深度比;并提出以双排桩的最大侧移增长百分比是否>20%作为依据,初步评价内坑开挖对基坑安全稳定性的影响程度;最后通过分析各参数对应工况下基坑破坏的模式和原因,针对性地给出了相应的解决措施。
Abstract
With a deep foundation pit project of Nanning Metro Line 4, we studied the supporting characteristics of double-row piles in round gravel mudstone composite stratum in Nanning using ABAQUS finite element software and field monitoring data, and concluded that double-row piles are well applicable in the round gravel mudstone composite stratum. We further investigated into the influence of pit-in-pit excavation on double-row piles under the conditions of different soil strength weakening percentages and the variations of pit toe coefficient and depth ratio around thresholds. Our findings suggest that the weakening of soil strength has the greatest influence on the supporting effect of double-row piles, followed by pit toe coefficient and depth ratio in sequence. Meanwhile, we propose to take whether the maximum increase percentage of lateral displacement of double-row piles exceeds 20% as the criterion to assess the influence degree of inner pit excavation on the safety and stability of foundation pit. In addition, by analyzing the failure modes and causes of the foundation pit under corresponding working conditions of each parameter, we gave corresponding countermeasures.
关键词
双排桩 /
坑中坑 /
圆砾-泥岩组合地层 /
数值模拟 /
安全系数
Key words
double-row piles /
pit-in-pit /
round gravel-mudstone mixed strata /
numerical simulation /
safety factor
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基金
国家自然科学基金项目(51768006,51978179);广西科技计划项目(桂科AB17195035)
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