考虑剪切错台变形的软土盾构隧道纵向结构计算模型研究

Shield tunnels in soft deposits are often suffered from significant longitudinal structural deformation during their long-term operation. Previous studies indicated that the longitudinal deformation of the tunnel structure is composed of the flexure deformation and the shear deformation. Current structural design of shield tunnels has been focused on the cross-sectional analysis on a single ring; the additional internal forces induced by longitudinal deformation of tunnel haven’t been taken in account. Meanwhile, previous longitudinal structural analyses are mainly based on the flexure deformation of the tunnel; the longitudinal structural model considering the shear deformation has not been seen yet. This research proposal will use the combination of field investigation, analytical method, laboratory test to solve the scientific problems of the longitudinal structural analysis: i) to propose a longitudinal structural model considering both the flexure deformation and the shear deformation of the tunnel based on the Timoshenko theory; ii) to determine the equivalence longitudinal stiffness and to verify the rationality of the model based on the laboratory test; iii) to establish an analytical model for the soil-tunnel structure interaction behavior analysis based on the proposal longitudinal structural model and the elastic foundation theory, and to present the closed-form solutions for a tunnel resting on an elastic foundation subjected to any given pressure loading. The soil-tunnel structure is verified by field data. This study is benefit to improve the study of the longitudinal deformation of shield tunnels and provide theoretical support for design of the tunnel structure. The research results will have important theoretical meaning and practical engineering value for the safety and durability protection of shield tunnels in soft deposits.

软土地层盾构隧道在长期运营中极易产生沿隧道轴向的纵向结构变形。隧道结构的纵向变形包括弯曲变形和环间剪切错台变形。目前盾构隧道结构设计仅取单环进行横向结构受力分析，未考虑沿纵向传递的结构变形与内力。现有的隧道纵向结构分析以弯曲变形为基础，缺乏能考虑剪切错台变形的纵向结构理论模型。本项目拟采用现场实测数据分析、理论分析、室内试验等技术手段，解决隧道纵向分析的关键科学问题：①基于Timoshenko理论建立能考虑隧道管片环间剪切错台变形的隧道纵向结构模型；②通过室内试验确定隧道纵向等效刚度并对模型加以验证；③将提出的隧道纵向隧道模型与弹性地基梁理论相结合，建立土-隧道相互作用的理论模型，给出任意荷载下隧道变形和内力计算方法，并以现场实测数据加以验证。研究成果预期可以丰富隧道纵向结构变形的理论研究，为盾构隧道纵向结构设计提供理论基础，对软土地层盾构隧道结构安全性和耐久性保护具有重要的理论指导意义。

当前隧道纵向结构计算模型为将以管片环的刚体转动为纵向变形形式欧拉梁，环间以张开变形为特征。然而大量的现场观测发现隧道纵向为剪切错台变形。本研究针对现有研究的不足提出考虑环间剪切变形的隧道纵向结构铁木辛柯梁等效模型，并推导了考虑纵向接头弱化影响的等效弯曲刚度和等效剪切刚度计算方法，给出隧道环缝张开量和环间错台量的定量计算公式。基于提出的纵向结构模型，提出土-隧道相互作用模型，并给出任意荷载作用下隧道结构内力和变形的解析方法。研究成果对隧道纵向结构的安全和耐久性设计以及运营保护具有重要的理论意义和工程实用价值。