既有匝道桥梁桩基托换实施方案研究

Research on Implementation Scheme for Underpinning Existing Ramp Bridge Pile Foundations

摘要:

为解决某市快速路高架匝道桥下部隧道施工中桩基托换及对上部结构扰动的问题，提出一套主动体系转换的桩基托换施工方案：采用现浇预应力混凝土抱柱托换梁，并布置液压千斤顶实施两次主动顶升转换，施工过程划分为施工准备、托换梁浇筑、首次体系转换、二次体系转换与收尾五个阶段；对托换梁、系梁及桥墩–托换梁结合面开展了承载性能与变形校核，并结合有限元模拟对施工期与临时运营期内的应力、挠度及沉降响应进行了验证。项目实施完成后，全过程沉降与变形可控，施工顺序与技术措施能够有效降低对上部结构的扰动，为类似复杂条件下的桩基加固与下部空间开发提供可借鉴的实践经验。

Abstract:

An active system-transfer scheme for pile foundation underpinning is proposed to address the challenges of pile foundation underpinning and disturbance to the superstructure during tunnel construction beneath an existing elevated ramp bridge of an urban expressway. The prestressed concrete pouring is adopted to support the columns and replace the beams, and the hydraulic jack is arranged to carry out two active lifting transitions. The construction process is divided into five phases of construction preparation, underpinned beam pouring, first system transition, second system transition and completion. Checks of bearing capacity and deformation are conducted for the underpinned beams, tie beams, and pier-underpinned beam interfaces. Stress, deflection and settlement responses during construction and temporary operation periods are verified with finite element simulation. After the project implementation is completed, the entire process of settlement and deformation can be controlled. The construction sequence and technical measures can effectively reduce the disturbance to the superstructures, offering the practical experience for pile foundation reinforcement and subsurface space development under similar complex conditions.