地铁双线隧道施工对其穿越桥梁安全性分析

Safety Analysis on the Bridge Traversed by Metro Double-Line Tunnels

地铁隧道施工经常有穿越既有桥梁基础的现象,穿越施工对桥梁造成的潜在威胁受业内普遍重视.北京地铁奥运支线工程奥体中心站—奥林匹克公园站区间隧道(简称奥—奥区间)为双线隧道,在北辰桥处南北向垂直横穿北四环路.北辰桥上部由3座跨线桥构成.为提高桥梁的整体性和抗沉降能力,桥墩基础在设计时已考虑了下穿地铁区间的影响,但是奥—奥区间隧道在施工过程中,不可避免地会对北辰桥产生扰动,从而引起U形槽结构和桥墩的附加沉降.本文以区间隧道穿越北辰桥施工为例,基于FLAC 3D建立的三维模型,对由于双线隧道穿越既有桥梁施工引起的桥梁沉降与变形进行了全过程计算和分析,并对2号桥的盖梁内力进行了检验.结果表明,桥梁构件的变形指标与内力指标都低于容许限值要求.现场监测数据也证明该施工方法的可行性.

Construction of metro tunnel traversing the existing urban bridge foundation is an ordinary form. Bridge safety menaced by traversing construction of metro section tunnel is highly concerned. Beisihuan Road of Beijing was traversed by the section tunnel with double lines between Olympic Sports Center Station and Olympic Park Station under Beichen Bridge along the north-south direction. Beichen Bridge is composed of three flyover bridges. For enhancing the global integrity and improving the deformation resisting capacity of the bridges, the foundation under bridge piers was specially designed and disposed as an integral reinforced concrete U-shape groove foundation considering the influence of the traversing construction of the section tunnel. During the construction of the section tunnel, disturbance on Beichen Bridge is inevitable, which resulted in the additional settlement between the U-shape groove foundation and bridge piers. In this paper, based on the three dimensional model set up in FLAC 3D, the traversing construction of section tunnel through Beichen Bridge in Beijing was taken as a example, and the settlement and deformation caused by the traversing construction of double-line tunnels of the existing bridge structures were calculated and analyzed in detail for the whole construction procedures. Subsequently, the inner forces of cap beams of No. 2 Bridge were checked. The calcu-lating results show that the deformation indices and the inner forces of the bridge components were lower than the corresponding allowable limit value. The availability of the construction method was validated by the monitoring data recorded in-situ.