基坑开挖卸荷对坑底管桩承载性状影响研究  

Study of Pipe Pile Bearing Characteristic in Foundation Pit for Excavation and Unloading

作　　者：杨庆光[1] 陈小巍 贺敏 刘杰[1] 何杰[1] Yang Qingguang;Chen Xiaowei;He Ming;Liu Jie;He Jie(College of Civil Engineering,Hunan University of Technology,Zhuzhou,Hunan 412007,P.R.China;Team 416,Hunan Provincial Bureau of Geology and Mineral Exploration and Development,Zhuzhou,Hunan 412007,P.R.China)

机构地区：[1]湖南工业大学土木工程学院,湖南株洲412007 [2]湖南省地质矿产勘查开发局四一六队,湖南株洲412007

出　　处：《地下空间与工程学报》2023年第3期777-783,共7页Chinese Journal of Underground Space and Engineering

基　　金：国家自然科学基金(51978260,51909086);湖南省自然科学基金(2020JJ6080,2020JJ5131);湖南省教育厅一般项目(18C0505)。

摘　　要：对于先地面成桩后基坑开挖的坑底管桩基础,基坑开挖卸荷会对坑底管桩成桩挤土效应产生弱化效应,进而对管桩竖向承载力造成影响,而这方面的研究较少。本文基于Vesic圆孔扩展理论,在考虑基坑开挖卸荷对管桩挤土效应影响的基础上,建立了开挖卸荷影响下坑底管桩竖向承载力折减系数k计算方法。通过室内模型试验,对比研究开挖前后静压桩和钻孔桩荷载-沉降关系特征。结果表明:开挖卸载对静压桩极限承载力所对应变形量变化量是钻孔桩的3倍;沉降量相同时,竖向承载力折减系数k试验值为0.856,与计算值0.833相差仅为2.72%,但明显低于钻孔桩承载力折减系数k试验值0.923。此外,计算结果表明:折减系数k与基坑开挖深度/管桩桩长(H/L_(0))比值变化曲线表现出明显非线性特征,且δ取值改变对k值影响较k_(0)和c取值变化对k值影响更为显著。本文研究成果能为坑底管桩承载力设计提供有益参考。To pipe pile installed before excavation under foundation pit,the soil squeezing effect for installation of pipe pile is weakened under foundation pit.For excavation and unloading of foundation pit,the vertical bearing capacity of pipe pile will been affected which has rarely been studied.Based on cavity expansion theory of Vesic and considering the influence of soil squeezing effect of pipe pile for excavation and unloading,the computing method of reduction coefficient k of bearing capacity is proposed for excavation of foundation pit in this paper.By indoor model test,the load-displacement relationship of jacked pile is compared with bored pile.It is indicated that the displacement increment of unlimate bearing capacity of jacked pile is three times that of bored pile for excavation of foundation pit.The reduction coefficient k of bearing capacity measured is 0.856 which has 2.72%difference with 0.923 calculated by method in this paper.Moreover,the calculation result indicates that the curve of k and H/L_(0) shows a significant nonlinearity and the change ofδhas more significant effect on k than k_(0) and c.The study can provide useful references for bearing capacity design of pipe pile in foundation pit.

关 键 词：管桩 挤土效应 承载力折减系数 承载性状 开挖卸载 

分 类 号：TU473.1[建筑科学—结构工程]