Abstract:

As more and more urban rail transit works are built, some Metro lines have to pass through dense building/structure areas. In this paper, the scheme of Tianjin Metro Line 5 to cross Dongfeng Interchange is analyzed, and the arrangement of the Metro stations, the design of the shieldbored running tunnels and the underpinning of the existing bridge piles are studied in detail. Conclusions drawn are as follows: 1) The scheme of updown overlapping tunnel tubes adopted has such advantages as occupying less underground space, increasing the freedom of the Metro line, avoiding some existing pile foundations, reducing the demolition and resettlement and reducing the construction cost; 2) The lower tunnel tube should be built before the upper one, and countermeasures including steel support and grouting should be taken, which can reduce the mutual effect between the tunnel tubes; 3) Active underpinning should be adopted for the foundation piles of the ramp bridge, which can effective control the settlement o f the piers. 

Key words: Tianjin Metro, dense building/structure area, largescale interchange, Metro line layout, environmental impact, overlapping tunnel, shieldbored running tunnel, pile foundation underpinning