沉管隧道半刚性管节节段接头力学性能研究

Structural and waterproof safety of joint is the key issue of immersed tunnel construction all the time. The semi-rigid element structure, remaining temporary prestressed cables, is to solve differential settlement problem under conditions of deep soft foundation and large siltation. However, it will not only improve the structural safety of segmental joints, but will have a notable influence on mechanical characteristics of segmental joint system, when transferring flexible elements to semi-rigid elements. Therefore, this has raised a new issue for theories and technologies of immersed tunnel joints. This project will conduct a deep research on segmental joint mechanical properties of semi-rigid elements under the action of prestressed cables, by means of model tests, numerical simulations and theoretical analysis, basing on building and already built actual projects. The aim of this project is to divide segmental differential settlement types and loading modes. Further more, it will reveal affect mechanism of prestressed cables on anti-shearing ability and anti-bending stiffness of segmental joints. Besides, it will build a mechanical analysis model and a calculate method of internal forces and opening values for semi-rigid element segmental joints. In addition, it will put forward opening and settlement tolerance values of semi-rigid elements in accordance with segmental joint mechanical properties. This project will supplement joint theoretical system and provide scientific basis for relating design standards or norms, which has a significantly social and economic benefits.

接头防水与结构安全始终是沉管隧道建设的关键问题。为应对厚软基、大回淤等条件下的工后差异沉降，采用保留临时预应力拉索的半刚性管节结构形式，在提高节段接头安全的同时，也使得管节由柔性转变为半刚性，其接头体系的力学特征将产生深刻变化，从而对沉管接头理论与技术提出了新的研究课题。本项目将结合已建、在建实体工程，在对大量现有实测资料深入分析的基础上，通过模型试验、数值模拟与理论分析等手段对预应力拉索作用下的半刚性管节节段接头力学性能进行深入研究。旨在系统划分沉管节段差异沉降类型与接头受力模式；揭示预应力拉索对节段接头抗剪性能与抗弯刚度的影响机理；建立半刚性管节节段接头力学分析模型，提出节段接头内力与张开量计算方法；基于节段接头力学性能提出半刚性管节节段接头张开量与差异沉降控制指标。通过本项目的研究，不仅可以完善沉管接头理论体系，还可以为相应设计规范的制定提供必要的科学依据，社会与经济效益显著。

接头防水与结构安全是沉管隧道建设的关键问题。半刚性管节在提高节段接头安全的同时，也使得管节由柔性转变为半刚性，从而对沉管接头理论与技术提出了新的研究课题。本项目在对大量现有实测资料深入分析的基础上，通过模型试验、数值模拟与理论分析等手段对预应力拉索作用下的半刚性管节节段接头力学性能进行深入研究。得出了以下研究成果：(1)将沉管节段接头变形类型与接头受力模式划分为：张角（弯剪）、错动（直剪）与转角（扭剪）。(2)对比分析了半刚性管节与柔性管节节段接头剪力键破坏特征与破坏过程，阐明了半刚性管节节段接头剪力键破坏机理，相比柔性管节节段接头剪力键的局部破坏，半刚性管节节段接头剪力键呈整体破坏，且相比柔性管节节段接头其允许接头变形值更小。(3)揭示了预应力拉索对节段接头抗剪性能与抗弯刚度的影响机理。预应力拉索通过提高接头摩擦来提供接头抗剪能力，随着接头变形量增大接头抗剪刚度不断降低，提高预应力拉索初始索力可以提高接头抗剪刚度；靠近弯转中心一侧预应力拉索对接头抗弯作用恒定且作用很小，远离弯转中心一侧预应力拉索随着接头张角的增大而增大；随着张角的增大，半刚性管节节段接头抗弯刚度快速降低，提高预应力拉索初始索力可以提高半刚性管节节段接头抗弯刚度。(4)对半刚性管节节段接头抗弯、抗剪刚度进行了定义；建立了半刚性管节节段接头“接头-刚度”力学分析模型，并提出半刚性管节节段接头刚度与内力计算方法。(5)基于节段接头剪力键力学性能，提出了半刚性管节节段接头允许张开量（0.13°）与节段两端差异沉降控制指标（0.0023L）。通过本项目的研究，不仅可以完善沉管接头理论体系，还可以为相应设计规范的制定提供必要的科学依据，社会与经济效益显著。