SAFETY ANALYSIS ON THE BRIDGE TRAVERSED BY METRO DOUBLE-LINE TUNNELS

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. 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 to considerate 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, taking the traversing construction of section tunnel through Beichen Bridge in Beijing as a case, based on the three dimensional model set up in FLAC-3D, the settlement and deformation due to 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. It was shown from the calculating results 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.