不同初始固结度欠固结软土中单桩负摩阻力模型试验研究

doi:10.13722/j.cnki.jrme.2023.1110

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摘要欠固结软土地基主固结尚未完成，在工程建设及使用过程中易产生过大沉降，引起桩基产生负摩阻力。鉴于现有研究缺乏对欠固结土欠固结程度的定量分析，更是鲜有软土欠固结程度对桩基负摩阻力特性影响方面的研究，本文定义初始固结度表征土体的欠固结程度，考虑堆载工况，开展3组不同初始固结度下的单桩模型试验，探究不同初始固结度桩周土、不同堆载等级下桩基负摩阻力规律，获得负摩阻力系数和中性点深度。研究结果表明：初始固结度对桩基负摩阻力影响显著，随着土体初始固结度的增大(即欠固结程度的降低)，桩身沉降、土体沉降、桩身轴力以及桩侧负摩阻力均呈减小趋势，且其影响在不同加载等级下基本相似。初始固结度Uz = 0.25，0.50和0.75下负摩阻力系数均值分别为0.545，0.351和0.147，对比 = 0.25情况， = 0.50和0.75下的负摩阻力系数分别降低35.6%和73.0%。初始固结度增大引起中性点下移，但是下移速率会随着初始固结度的增大而逐渐降低， = 0.25，0.50和0.75下中性点深度分别为0.53，0.75和0.76倍的有效桩长。此外，当初始固结度相同时，荷载等级的增加引起负摩阻力系数小幅上升、中性点深度小幅下降，但总体影响不大。研究成果可为欠固结土中桩基负摩阻力分析和设计提供技术参考。

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	谷川1
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	杨益挺1
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	王军1
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	刘龙庆1
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	余楠1
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关键词 ：桩基工程, 欠固结土, 固结度, 负摩阻力, 中性点

Abstract：The primary consolidation of unconsolidated soft soil is not yet complete，so it is susceptible to producing excessive settlement，causing drag forces along the pile shaft installed in these soil layers. Few discussions on the bearing capacity of piles(i.e. negative frictional resistance) in underconsolidated soil have been reported，including the influence of the underconsolidation degree. In this paper，a parameter termed as initial consolidation degree，，was defined to characterize the underconsolidation degree，and three model tests were carried out under different initial consolidation degrees，in which surcharge preloading was considered. The behavior of the negative frictional resistance of the pile under different initial consolidation degrees and surcharge levels was analyzed，and the coefficient of negative frictional resistance and neutral point depth were discussed. The results show that the initial consolidation degree has a significant effect on the negative frictional resistance of pile. With the increase of (i.e.，the decrease of the underconsolidation degree of soil)，the settlement of pile，settlements of soil at different depths，axial force of pile shaft and negative friction resistance of pile all show a decreasing trend，and their behavior is basically similar under different loading levels. The average values of negative friction coefficient under = 0.25，0.50 and 0.75 are 0.545，0.351 and 0.147，correspondingly. Compared to = 0.25，the negative friction coefficients under = 0.50 and 0.75 are reduced by 35.6 % and 73.0 %，respectively. The increase of leads to the neutral point moving downward，but the downward rate gradually decreases. When = 0.25，0.50 and 0.75，the neutral point depths are 0.53，0.75 and 0.76 of the pile depth，correspondingly. In addition，the increase of the surcharge level causes the increase of negative friction coefficient and the decrease of neutral point depth slightly，but the effect is not significant in the holistic view when the initial consolidation degree is identical. The research results can provide technical reference for the analysis and design of negative friction resistance of piles in unconsolidated soft soil.

Key words： pile foundation unconsolidated clay consolidation degree negative friction neutral point

引用本文:

谷川1，2，3，杨益挺1，4，秦伟1，2，5，王军1，2，4，刘龙庆1，5，余楠1，3. 不同初始固结度欠固结软土中单桩负摩阻力模型试验研究[J]. 岩石力学与工程学报, 2024, 43(8): 2042-2055.
GU Chuan1，2，3，YANG Yiting1，4，QIN Wei1，2，5，WANG Jun1，2，4，LIU Longqing1，5，YU Nan1，3. Model test study on the negative skin friction of piles in unconsolidated soft soil with different initial consolidation degrees. , 2024, 43(8): 2042-2055.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2023.1110 或 http://rockmech.whrsm.ac.cn/CN/Y2024/V43/I8/2042

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