地铁区间隧道下穿既有桥梁的桩基托换研究

以深圳市地铁7号线黄木岗站区间隧道穿越华强立交桥桩基工程为背景,建立有限元模型,研究隧道下穿既有桥梁时桩梁式托换桩的主动托换和被动托换的荷载转化规律及桩基沉降规律。结果表明:被动托换的沉降主要由托换梁的挠曲变形引起,而主动托换时千斤顶的顶升作用可以有效抵消托换梁的挠曲变形;主动托换时,顶升位移为1.68 mm时为最佳截桩位置,此时截桩能有效减小托换工艺对桥梁上部结构影响;被动托换的总体施工前后桥墩柱顶面有较大隆起,不能满足桥面板平顺的要求。研究成果直接用于指导黄木岗站区间隧道现场施工,并可为今后类似工程提供参考。

Research on Pile Foundation Underpinning of Subway Running Tunnel Passing under Existing Bridge

Based on the pile foundation project where Shenzhen Metro Line 7 Huangmugang station tunnel passes under Huaqiang overpass,a finite element model is established to study the load transformation rule and pile foundation settlement laws of passive and active underpinning of pile and beam underpinned pile. The results show that the passive underpinning settlement is mainly caused by the bending deformation of underpinning beam,but the jacking effects of the jack can effectively offset bending deformation of the underpinning beam at the time of active underpinning; the top displacement of 1. 68 mm is the best position to cut the pile at the time of active underpinning,and it is the best time to effectively reduce the influence of underpinning process on the upper structure of the bridge; there is great uplift on the bridge pier column surface before and after the overall construction of passive underpinning, which fails to satisfy the requirement for smooth bridge deck. The researchresults are directly used to guide the Huangmugang station tunnel construction, and may provide reference for future similar projects.