长昆线桥隧相连设计研究

摘要

Research purposes: There are many sections of bridge - tunnel connection in Changsha - Yuping section on Shanghai - Kunming passenger dedicated line because of topographic relief effect. Various of difficulties exist in design of bridge - tunnel connection, such as whether tunnel portal can accommodate bridge abutment and effectively relieve aerodynamic effect of tunnel portal, drainage of portal in lower point of tunnel, transition of cable channels between bridge and tunnel, whether retaining wall outside of tunnel can effectively work and construct safely, and so on. In order to resolve the problem that bridge and tunnel are difficult to be connected in Changsha - Yuping section on Shanghai -Kunming passenger dedicated line, the special study on bridge - tunnel connection technology need to be done. Research conclusions: (1) In bridge - tunnel connection section in series, using enlarged cross - section and digging filling piles can effectively solve the problems that bridge abutment enters tunnel difficultly and aerodynamic effect exists in tunnel portal. (2) According to different portal types and lengths of open cut sections, excavation methods of bridge abutment pits are classified into two types: protection of digging filling piles and step - slope excavation behind the pit in bridge - tunnel docking connection section. ( 3) For the situation that retaining wall exists outside of the portal in bridge -tunnel docking connection section, the following two measures that pile foundation and joist are set under the retaining wall and the retaining wall is designed into anchor retaining wall, can solve the difficult problems that the retaining wall is unstable because of pit excavation. (4) By the measure that transition section is set in tunnel portal, cable channelscan link smoothly in bridge -tunnel connection section. (5)Inspection well which is set in the lower tunnel portal, caneffectively solve the drainage problem of tunnel.%研究目的:沪昆铁路客运专线长沙至玉屏段,沿线地形起伏,存在多处桥隧相连段落.在桥隧相连设计过程中,隧道洞门能否容纳下桥台结构并有效缓解洞口空气动力学效应、隧道低洞口端洞口排水、桥隧电缆槽对接过渡以及隧道洞外存在挡墙结构时挡墙是否能起到作用并能保证施工安全等,均存在较大的难点.为解决沪昆铁路客运专线长沙至玉屏段桥隧相连的工程难题,需对桥隧相连进行专门研究.研究结论:(1)采用扩大洞门横断面+挖孔灌注桩方案,能有效解决桥隧串接时桥台结构伸入隧道及洞口空气动力学效应等难题；(2)桥隧对接时,桥台基坑可根据条件的不同分别采用台后挖孔灌注桩防护和台后放坡两种方式开挖；(3)对于桥隧对接时洞门结构外存在挡墙的情况,在挡墙下设桩基+托梁,并将挡墙设计为锚杆挡墙,可以解决桥台基坑开挖引起挡墙结构不稳的难题；(4)通过在隧道内设置过渡段,可有效地将桥梁与隧道电缆槽顺接起来；(5)隧道内低洞口端设置洞口检查井汇集洞内水体,能有效解决洞内排水问题.