盾构施工诱发软土地层变形机理及解析解

    MECHANISMS AND ANALYTICAL SOLUTIONS FOR SOFT-GROUND DEFORMATION INDUCED BY SHIELD TUNNELING

    • 摘要: 软土地层盾构施工往往会引起显著地表沉降,但目前盾构施工诱发的地表沉降研究主要依赖于现场监测及数值模拟,基于力学背景的理论解析及对应验证分析较少。本文将盾构施工地层变形分解为:盾构推力引起的沉降(wq)、盾壳摩阻引起的沉降(wf)、地层损失引起的沉降(wv)以及同步注浆引起的沉降(wp),在局部坐标系中基于Mindlin解和Sagaseta解推导了上述各沉降分量的计算公式,从而在整体坐标系中建立了盾构施工地表沉降的理论计算模型,并进行了以隧道埋深及地层损失为控制因素的参数分析。结果表明,wqwfwvp在地表总沉降量w中所占比例分别约为3% ~6%、5% ~7%和80% ~90%;wqwvp与隧道埋深H呈负相关关系、wf与隧道埋深呈正相关关系、地表总沉降量w与隧道埋深H之间符合自然指数函数关系,当埋深由18 m减小至6 m时,总沉降量w增幅达76.5%;超挖量对总沉降量w及4种沉降分量的分布范围影响不显著,但总沉降量w与开挖半径R之间呈现显著的线性关系,当R由3.2 m增加至3.5 m时,总沉降增加156%。研究结论为软土地层地铁隧道设计及盾构施工参数控制,尤其是浅埋隧道盾构施工提供了数据基础及计算依据。

       

      Abstract: Shield tunneling in soft ground can induce pronounced ground surface settlement, posing a potential risk to adjacent infrastructure. Although shield-induced settlement has been extensively investigated through field monitoring and numerical simulation, mechanics-based analytical studies with systematic validation remain relatively limited. In this study, the ground deformation induced by shield tunneling is decomposed into four components: shield thrust-induced settlement(wq), shield-soil friction-induced settlement(wf), ground loss-induced settlement(wv), and synchronous grouting-induced deformation(wp).Based on Mindlin's and Sagaseta's solutions, analytical expressions for these settlement components are derived in local coordinate systems, transformed into a global coordinate system, and subsequently superimposed to establish an analytical model for predicting shield tunneling-induced surface settlement. Parametric analyses are then performed by considering tunnel burial depth and ground loss as the controlling variables. The results indicate that(wq), (wf), and(wvp), where wvp denotes the combined contribution of ground loss and synchronous grouting, account for approximately 3% ~6%, 5% ~7%, and 80% ~90% of the total settlement w, respectively. Both wq and wvp decrease with increasing tunnel burial depth H, whereas wf shows an increasing trend. The total surface settlement w exhibits a negative exponential relationship with H; specifically, when H decreases from 18 m to 6 m, w increases by 76.5%.Over-excavation has a limited influence on the spatial distribution of w and its individual components but significantly affects their magnitudes. A strong linear relationship is observed between the total settlement w and the excavation radius R; when R increases from 3.2 m to 3.5 m, the total settlement increases by 156%.This study provides a mechanics-based analytical framework for quantifying the contribution of different shield tunneling processes to surface settlement and offers theoretical support for settlement prediction and deformation control in soft-ground tunneling. The findings of this study provide a data foundation and computational basis for the design of metro tunnels in soft soil formations and the control of shield construction parameters, particularly for shield construction in shallow-buried tunnels.

       

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