多因素影响下盾构掘进对紧邻桩基的三维位移的影响

Three-dimensional displacement characteristics of adjacent pile induced by shield tunneling under influence of multiple factors

城市核心区内采用盾构法修建地铁隧道时将不可避免地穿越大量桩基础,准确评估紧邻桩基受盾构开挖引起的潜在风险成为关注的重点。本文采用两阶段分析法研究了桩-土-隧道的相互作用机理。第一阶段基于Mindlin解推导了盾构顶推力、刀盘摩阻力、盾壳摩阻力和管片壁后注浆压力作用下的三维土体位移场,通过引入Pinto三维地层损失公式,构建盾构开挖引起的完整三维土体位移解析解,完善了Loganathan分析土体位移场时没有考虑盾构施工因素,仅能得到二维土体位移场的不足。第二阶段基于Pasternak双参数地基模型推导分层地基中盾构隧道施工对紧邻桩基位移的三维解析解。以长沙地铁5号线万家丽广场—芙蓉区政府区间盾构近距离侧穿高架桩基为工程背景,建立三维有限元模型。结合现场监测数据,对比三维解析解、有限元模拟得到的土体和桩基沿隧道纵向、水平向和竖向位移,验证了本文所提三维解析解的可靠性,为此类工况提供了相应的理论基础,具有重要的工程指导意义。

Shield tunneling inevitably passes through a large number of pile foundations in urban areas.Thus,an accurate assessment of tunneling-induced pile displacement and potential damage becomes a critical part of shield construction.This study presents a mechanism research of pile-soil-tunnel interaction through Pasternak-based two-stage analysis method.In the first stage,based on Mindlin’s solution,the soil displacement fields induced by shield thrust force,cutterhead frictions,shield shell frictions and grouting pressure are derived.The analytical solution of threedimensional soil displacement field is established by introducing Pinto’s three-dimensional volume loss formula,which solves the problems that shield construction factors are not taken into account in Loganathan’s formula and only twodimensional soil displacement field can be obtained.In the second stage,based on Pasternak’s two-parameter foundation model,the analytical solution of pile displacement induced by shield tunneling in layered soil is derived.A case was found in the project of interval tunnels from Wanjiali Square to Furong District Government of Changsha Metro Line 5,where the shield tunnels were constructed near viaduct piles.The reliability of the analytical solution proposed in this study is verified by comparing with the field measured data and the results of finite element method(FEM).In addition,the comparisons of longitudinal,horizontal and vertical displacements of soil and pile foundation analyzed by the analytical solution and FEM provide corresponding theoretical basis,which has significant engineering guidance for similar projects.