软土地区盾构施工对既有单桩工作性状的影响分区研究
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摘要
为研究既有桩基位于拟建隧道周围不同位置时,隧道开挖对桩基产生的受力与变形规律,依托天津地铁3号线北站至铁东路站左线盾构区间项目,利用ABAQUS软件将隧道周围软土按照桩端径向、切向位置的不同划分为8个区,建立考虑软土修正剑桥本构关系的二维有限元模型,探讨隧道开挖后桩基分别处于设计荷载和极限荷载下的桩侧摩阻力和桩身位移变化规律,并建立隧道开挖对邻近单桩工作性状的影响分区。计算结果表明:1)隧道开挖会使桩基近隧道侧产生负摩阻力,负摩阻力最大值随桩到隧道径向距离的减小而逐渐增大,随桩长的增大而逐渐增大;2)隧道开挖会导致桩身极限侧摩阻力降低,当桩端位于隧道两侧分区时降幅较大,在10%～15%;3)桩端分别位于隧道两侧、底部、顶部分区时,依次对桩身倾斜率、桩身挠曲变形和桩顶沉降的影响最显著;4)提出能够对隧道开挖后既有单桩工作性状分区进行评价的指标,当桩端位于3区时,盾构隧道开挖造成单桩的综合影响程度最大,应加强施工监控措施。
It is very important to study the stress and deformation law of pile foundation caused by tunnel excavation when the existing pile foundation is located in different positions around the tunnel. Firstly, the soft soil around the shield section project of left line of North Station-Tiedong Road Station on Tianjin Metro Line No. 3 is divided into 8 zones according to the radial and tangential positions of pile end by ABAQUS software. And then a two-dimensional finite element model considering soft soil modified Cambridge constitutive relation is established to study the lateral friction resistance and displacement of pile body under design load and ultimate load after excavation of tunnel. Finally, the influence zone of tunnel excavation on the behavior of adjacent single pile is established. The results show that:(1) Tunnel excavation will cause negative friction resistance on the side near the tunnel of pile foundation; and the maximum negative friction resistance increases with the decrease of radial distance between pile and tunnel, and increases with the increase of pile length.(2) The excavation of the tunnel will lead to the reduction of the ultimate lateral friction resistance of the pile body; and when the pile end is located on both sides of the tunnel, the decrease amplitude is much higher, ranging from 10% to 15%.(3) When the pile end is located on both sides of the tunnel, the bottom and the top of the tunnel, the tunnel excavation mainly affects the inclination of the pile body, the deflection of the pile body and the settlement of the pile top.(4) The inddices that can evaluate the behavior of existing single pile after tunnel excavation are put forward; when the pile end is located in zone 3, the comprehensive influence of shield tunneling on single pile is the largest, and construction monitoring measures should be strengthened.
It is very important to study the stress and deformation law of pile foundation caused by tunnel excavation when the existing pile foundation is located in different positions around the tunnel. Firstly, the soft soil around the shield section project of left line of North Station-Tiedong Road Station on Tianjin Metro Line No. 3 is divided into 8 zones according to the radial and tangential positions of pile end by ABAQUS software. And then a two-dimensional finite element model considering soft soil modified Cambridge constitutive relation is established to study the lateral friction resistance and displacement of pile body under design load and ultimate load after excavation of tunnel. Finally, the influence zone of tunnel excavation on the behavior of adjacent single pile is established. The results show that:(1) Tunnel excavation will cause negative friction resistance on the side near the tunnel of pile foundation; and the maximum negative friction resistance increases with the decrease of radial distance between pile and tunnel, and increases with the increase of pile length.(2) The excavation of the tunnel will lead to the reduction of the ultimate lateral friction resistance of the pile body; and when the pile end is located on both sides of the tunnel, the decrease amplitude is much higher, ranging from 10% to 15%.(3) When the pile end is located on both sides of the tunnel, the bottom and the top of the tunnel, the tunnel excavation mainly affects the inclination of the pile body, the deflection of the pile body and the settlement of the pile top.(4) The inddices that can evaluate the behavior of existing single pile after tunnel excavation are put forward; when the pile end is located in zone 3, the comprehensive influence of shield tunneling on single pile is the largest, and construction monitoring measures should be strengthened.
引文
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[14]龚晓南.桩基工程手册[M].2版.北京:中国建筑工业出版社,2016.GONG Xiaonan.Handbook of pile foundation engineering[M].2nd ed.Beijing:China Architecture&Building Press,2016.
[15]费康,张建伟.ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010.FEI Kang,ZHANG Jianwei.Application of ABAQUS in geotechnical engineering[M].Beijing:China Water&Power Press,2010.
[2]黄茂松,李早,杨超.隧道开挖条件下被动群桩遮拦效应分析[J].土木工程学报,2007,40(6):69.HUANG Maosong,LI Zao,YANG Chao.Analysis of the shielding effect of a pile group adjacent to tunneling[J].China Civil Engineering Journal,2007,40(6):69.
[3]王立峰.盾构施工对桩基的影响及桩基近邻度划分[J].岩土力学,2014,35(增刊2):319.WANG Lifeng.Shield construction influences on piles and classification of adjacent pile degree[J].Rock and Soil Mechanics,2014,35(S2):319.
[4]LEE G T K,NG C W W.Effects of advancing open face tunneling on an existing loaded pile[J].Journal of Geotechnical and Geoenvironmental Enginering,2005,131(2):193.
[5]徐明,谢永宁.盾构隧道开挖对邻近单桩基础的影响[J].华南理工大学报(自然科学版),2011,39(4):149.XU Ming,XIE Yongning.Effect of shield tunneling on adjacent single-pile foundation[J].Journal of South China University of Technology(Natural Science Edition),2011,39(4):149.
[6]王丽,郑刚.盾构法开挖隧道对桩基础影响的有限元分析[J].岩土力学,2011,32(增刊1):704.WANG Li,ZHENG Gang.Finite element analysis of effects of shield driven tunneling on pile foundation[J].Rock and Soil Mechanics,2011,32(S1):704.
[7]王丽,郑刚.盾构法隧道施工对邻近摩擦单桩影响的研究[J].岩土力学,2011,32(增刊2):621.WANG Li,ZHENG Gang.Research on effects of shield driven tunneling on adjacent single friction-pile[J].Rock and Soil Mechanics,2011,32(S2):621.
[8]ZHENG Gang,LU Ping,DIAO Yu.Advance speed-based parametric study of greenfield deformation induced by EPBMtunneling in soft ground[J].Computers and Geotechnics,2015,65:220.
[9]张云.修正剑桥模型参数对计算结果的影响[J].岩土力学,2006,27(3):441.ZHANG Yun.Effects of parameters of modified Cambridge model on computed results[J].Rock and Soil Mechanics,2006,27(3):441.
[10]杨冠天,项彦勇,刘峰.盾构隧道周围地层变形解析法的运用[J].现代隧道技术,2004,41(2):21.YANG Guantian,XIANG Yanyong,LIU Feng.Application of an analytical method for predicting the ground deformation induced by shield tunneling[J].Modern Tunnelling Technology,2004,41(2):21.
[11]黄宏伟,徐凌,严佳梁.盾构隧道横向刚度有效率研究[J].岩土工程学报,2006,28(1):11.HUANG Hongwei,XU Ling,YAN Jialiang.Study of transverse effective rigidity ratio of shield tunnels[J].Chinese Journal of Geotechnical Engineering,2006,28(1):11.
[12]民用建筑可靠性鉴定标:GB 50292-2015[S].北京:中国建筑工业出版社,2015.Standard for appraisal of reliability of civil buildings:GB50292-2015[S].Beijing:China Architecture&Building Press,2015.
[13]铁道综合技术研究所.接近既有铁路隧道施工对策指南[S].[S.l.:s.n.],1996.Railway Comprehensive Technology Research Institute.Countermeasures guide for tunnel construction close to existing railway[S].[S.l.:s.n.],1996.
[14]龚晓南.桩基工程手册[M].2版.北京:中国建筑工业出版社,2016.GONG Xiaonan.Handbook of pile foundation engineering[M].2nd ed.Beijing:China Architecture&Building Press,2016.
[15]费康,张建伟.ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010.FEI Kang,ZHANG Jianwei.Application of ABAQUS in geotechnical engineering[M].Beijing:China Water&Power Press,2010.