新建桥涵上跨运营隧道保护方案及措施研究

Research on the Protection Scheme and Measures of Newly Built Bridges and Culverts Over-crossing Operating Subway Tunnels

研究目的:运营地铁隧道正上方作为轨道交通的特别保护区,为了减少对下卧隧道的影响,上方拟建项目设计方案多工序繁复、造价高且施工工期长。本文通过对某运营隧道上方新建桥涵工程设计方案和施工过程的综合研究,拟找到一种工艺简单、工程费用低,施工快捷且对地铁保护较好的解决方案。研究结论:(1)基于基坑卸载回弹相关研究和时空效应原理,新建桥涵采用预制箱涵拼装方案,土体小块开挖、结构分块快速吊装回筑,施工过程配重快速动态荷载平衡等措施,可以减少隧道上方土体应力变化幅度、范围以及变化的时间跨度,有利于控制对下卧地铁隧道结构的变形影响;(2)数值分析结果及实测数据表明,设计和施工统筹考虑的轨道保护方案对隧道变形的控制较好;(3)研究案例实施快捷、工程造价低、卸载再加载过程对地铁影响较小,可为其他上穿隧道工程的设计和施工提供借鉴和参考。

Research purposes:The upper part of the subway tunnel is used as a special protection area for rail transit.In order to reduce the impact on the subway in operation,the design scheme of the proposed construction project above is complicated with multiple procedures,high cost and long construction period.In this paper,the design scheme of a new bridge and culvert project above an operational tunnel is studied,to find a solution with simple process,low engineering cost,fast construction and good subway protection.Research conclusions:(1)Some measures based on the foundation pit unloading rebound and the principle of space-time effect are implemented to decrease the amplitude,range and time of the stress change of the soil above the tunnel,such as the design of prefabricated assembly box culvert,small soil excavation,rapid hoisting and placement,dynamic load balance for the newly built bridge and culvert,and so on.The influences upon the deformation of the subjacent tunnel can be limited from the soil excavation.(2)From the results of simulation and field tests,it can be found that the tunnel deformation can be limited better with the subway protection plan of a comprehensive consideration of design and construction.(3)There are some obvious characteristics for the study project in this paper,such as fast construction,low engineering cost and low effects on the subway from the process of the unloading and reloading,which can provide reference for the design and construction of the other engineering projects of overpassing the tunnel.