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  

Model test study on the negative skin friction of piles in unconsolidated soft soil with different initial consolidation degrees

作　　者：谷川[1,2,3] 杨益挺 秦伟 王军 刘龙庆[1,5] 余楠 GU Chuan;YANG Yiting;QIN Wei;WANG Jun;LIU Longqing;YU Nan(College of Civil Engineering and Architecture,Wenzhou University,Wenzhou,Zhejiang 325035,China;Key Laboratory of Engineering and Technology for Soft Soil Foundation and Tideland Reclamation of Zhejiang Province,Wenzhou,Zhejiang 325035,China;Zhejiang International Science and Technology Cooperation Base of Ultra-soft Soil Engineering and Smart Monitoring,Wenzhou,Zhejiang 325035,China;Zhejiang Collaborative Innovation Center of Tideland Reclamation and Ecological Protection,Wenzhou,Zhejiang 325035,China;Wenzhou Key Laboratory of Trafic Piezoelectric Engineering Technology,Wenzhou,Zhejiang 325035,China)

机构地区：[1]温州大学建筑工程学院,浙江温州325035 [2]浙江省软弱土地基与海涂围垦工程技术重点实验室,浙江温州325035 [3]超软土工程技术与智能化监测浙江省国际科技合作基地,浙江温州325035 [4]浙江省滩涂整治工程及生态保护协同创新中心,浙江温州325035 [5]温州市交通压电工程技术重点实验室,浙江温州325035

出　　处：《岩石力学与工程学报》2024年第8期2042-2055,共14页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(52178349,52008318);温州市科技特派员专项项目(X2023102)。

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U_(z)=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U_(z)=0.25情况,U_(z)=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,U_(z)=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。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,U_(z),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 U_(z)(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 U_(z)=0.25,0.50 and 0.75 are 0.545,0.351 and 0.147,correspondingly.Compared to U_(z)=0.25,the negative friction coefficients under U_(z)=0.50 and 0.75 are reduced by 35.6%and 73.0%,respectively.The increase of U_(z)leads to the neutral point moving downward,but the downward rate gradually decreases.When U_(z)=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 identica

关 键 词：桩基工程 欠固结土 固结度 负摩阻力 中性点 

分 类 号：TU473[建筑科学—结构工程]