地铁施工引起邻近桥梁桩基差异沉降的概率分析  

PROBABILISTIC ANALYSIS OF TUNNELING-INDUCED DIFFERENTIAL SETTLEMENT OF A PILE-SUPPORTED URBAN OVERPASS

作　　者：何海健[1] 项彦勇[1] 刘维宁[1] 

机构地区：[1]北京交通大学土木建筑工程学院,北京100044

出　　处：《岩石力学与工程学报》2007年第A01期3257-3265,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：北京市科技计划重点资助项目(D0604003040421);北京轨道交通建设管理有限公司科研资助项目(DTKH2004010006)

摘　　要：地铁工程施工往往会使邻近桥桩发生沉降,如果绝对沉降或差异沉降过大,就会影响桥梁的正常使用与安全。借助有限元ANSYS程序,分析地铁施工过程中主要不确定因素对邻近桥桩沉降的影响。结果表明:(1)对于模型中所考虑的施工顺序,桩基之间的差异沉降值在一定范围内按对数正态分布变化。根据盖梁结构所能承受的最大差异沉降,计算得到的可靠度在可接受的范围内;(2)桩基之间的最大差异沉降值与桩底持力层以及桩身所在地层的弹性模量密切相关,且在短桩情形下桩底持力层的弹性模量比桩身土层的弹性模量对沉降的影响更大;(3)桩基之间的最大差异沉降、桩顶沉降、隧道拱顶上方地表的沉降与边墙上部及隧道底板下部地层的泊松比以及初衬的弹性模量和泊松比的相关性均不显著;而该范围地层的弹性模量却对各沉降值影响很大。在施工中,应通过桩底注浆提高持力层的弹性模量,从而减小端承桩的沉降;为减小隧道开挖引起的边墙收敛,施工中应保证风道拱部和边墙处的注浆效果。Metro construction may cause settlements of adjacent pile-supported overpass structures.If the settlement is excessive,it will affect the normal operation and safety of the overpass.A probabilistic analysis is conducted to study the influence of major uncertain factors on the settlements of piles by using the ANSYS.For the construction sequence considered in the study,the differential settlement between adjacent pile foundations assumes a logarithmic normal distribution.For the maximum allowable differential settlement of the superstructure,the calculated reliability is well within the acceptable range.The maximum differential settlement between the neighboring pile foundations is mostly correlated with the elastic moduli of the strata below the pile tip and around the pile shaft;and for the short piles,the influence of the stratum below the pile tip is more significant than that of the stratum around the pile shaft.The maximum differential settlement between the nearby pile foundations,the settlement at the pile tip and that of the ground surface are significantly influenced by the elastic moduli of the strata near the upper part of the side wall and below the tunnel floor,while the Poisson′s ratios of the strata,the elastic modulus and Poisson′s ratio of the primary lining only have trivial effects.For piles with end-bearing capacities,grouting below the pile tip enhances the elastic modulus of the soil and thus may reduce the pile settlement.For the sake of mitigating tunneling-induced convergence,grouting around the tunnel arch and the side walls should also be particularly paid attention to.

关 键 词：隧道工程 地铁施工 桩基 差异沉降 概率分析 

分 类 号：U45[建筑科学—桥梁与隧道工程]