Observed long-term differential settlement of metro structures built on soft deposits in the Yangtze River Delta region of China

In this study, the measured differential settlements of five metro lines built on soft deposits were analyzed. The different structural combinations at various characteristic locations in the metro lines were examined, including at 67 joints of stations and tunnels, 55 connecting passage locations, 4 wind well locations, and at 3 joints of U-shaped grooves and adjacent structures. Moreover, the differential settlement between the track slabs and the bridge piers of a 16.57 km long elevated structure was analyzed. The results showed that the settlements of ∼85% of the stations were less than those of adjacent shield tunnels, and the settlements at the connecting passages of ∼73% of the tunnels were greater than those on either sides of the tunnel. The wind well exhibited lower settlement than its adjacent tunnels. The settlement of the U-shaped groove was greater than that of its adjacent elevated structure, but was less than those of the cut-and-cover and shield tunnels. Approximately 86% of the track slabs exhibited arch deformation, and the settlements of the bridge piers were greater than those of the track slabs. The stiffness transition between the different structures should be considered in the design of metro structures on soft deposits.