基于大直径盾构隧道扩挖地铁车站结构接头力学性能研究

A construction method that a running tunnel of two tracks is constructed by large diameter shield machine and moreover a station is built by shallow mining method to enlarge large diameter shield tunnel can be regarded as a new approach to solve the construction problems of metro engineering with complex environmental conditions. In the process of enlarged excavation. the joint parts such as the seam between retained segments and demolished segments and the seam between retained segments and the cast-in-situ concrete structure are the weakness parts in the integral structure, The joint mechanical properties determine the deformation and bearing capacity of the metro station structure to a great extent. In this project, the joint parts mechanical properties such as the relative displacement and open amount of the joint seam, concrete stress near the joint seam, the bending stiffness and shear stiffness of the joint parts ,etc with different working conditions will be studied by the full-scale load test firstly. The mechanical properties and failure mode of the joint will be discussed. On the basis of load experiment research, the failure mode for key joints will be established. The mechanical model of the joint parts will be established based on beam-spring model. The three-dimensional discontinuous contact model will be used to simulate the construction process. The varying law of mechanical properties for these key joint parts and the overall mechanical properties of the station structure in the process of enlarged excavation will be discussed. The research result will be benefit to the structure design of metro station.

采用大直径盾构建造地铁单洞双线区间并在盾构隧道基础上扩挖形成地铁车站是解决城市复杂环境下地铁建设的一种新思路。在车站结构形成过程中，保留管片与被拆除管片之间的接头以及保留管片与现浇混凝土结构之间的接头是结构的薄弱环节，其力学性能在很大程度上制约车站结构整体力学性能。本项目以扩挖车站结构的接头为研究对象，对接头试件进行加载试验研究，探索在荷载作用下接头的接缝变形、接缝张开量、混凝土应力及接头抗弯刚度与抗剪刚度等参数的演变规律。在此基础上，结合理论分析，研究接头破坏模式。基于梁-弹簧理论，采用三维非连续接触模型建立接头力学模型和计算方法，研究扩挖工况下接头力学行为，为扩挖车站接头设计及车站结构设计提供理论指导。

采用大直径盾构建造地铁单洞双线区间并在盾构隧道基础上扩挖形成地铁车站是解决城市复杂环境下地铁建设的一种新思路。在车站结构形成过程中，保留管片与被拆除管片之间的接头以及保留管片与现浇混凝土结构之间的接头是结构的薄弱环节，其力学性能在很大程度上制约车站结构整体力学性能。. 结合北京地铁14号线将台站和高家园站的工程实践，研究大直径盾构隧道侧壁管片拆除形成扩挖通道对邻近保留管片力学行为的影响。研究结果表明拆除管片等施工在邻近保留管片上引起的附加压应力最大值约-2.33MPa。进行非对称拆除管片现场试验，试验结果表明非对称拆除管片会使车站结构承受很大的偏心载荷作用。为此提出分段跳仓拆除方案，实测结果表明该方案能有效控制非对称拆除管片产生的偏载效应。. 分析了国内现有的大直径盾构隧道扩挖地铁车站结构方案存在的不足，提出一种新的大直径盾构隧道扩挖地铁车站的塔柱式结构方案。基于新结构方案，展开保留管片+内衬与现浇混凝土连接接头的加载试验，揭示了接头抗弯刚度、抗剪刚度随接头弯矩的变化规律，得出此类接头的抗剪刚度为无穷大；采用接驳器和预埋钢板连接的接头，其有效抗弯刚度分别为44.12×104 kN•m/rad～49.51×104 kN•m/rad和12.57×104 kN•m/rad～19.42×104 kN•m/rad。此外，进行开口型大直径盾构隧道双层衬砌结构加载试验，弄清了在车站结构接头的影响下，该结构的管片和内衬力学性能随覆土深度的变化规律，揭示了结构接头对结构整体力学性能的影响。. 研究了PBA法扩挖施工过程中车站结构关键节点受力和变形变化规律。研究结果表明：盾构隧道和车站两边主体结构的施工，对管片纵缝张开和错台影响显著；横通道施工对管片纵缝的张开和错台影响较小，但塔柱环和开口环管片的环间错台急剧增加，最大错台量达2.73 mm；管片接头压应力在扩建施工阶段均明显增大，最大值达-19.31 MPa；管片和现浇混凝土连接接头的张开和错台均不明显。本项目的研究成果为此类工法的推广应用提供技术储备。.