The Amsterdam North/South Metro line is a challenging project in an unfavourable urban environment of very soft soil and over 1000 historical buildings founded on wooden piles close to the tunnels. The two shield driven tunnels are 6.5 m in diameter. At Bridge 404 the tunnels are stacked, thus the tunnels pass under the bridge at different depths. Bridge 404 is a historical bridge founded on brick abutments, which in turn are supported on driven wooden piles 13 m below surface level. The crown of the deep tunnel is situated 12 m below the pile tips but the shallow tunnel has a clearance of only 1.5 m below the pile tips. As the cover under the canal is reduced and the loads of the piles have a significant impact on the stability of the bore front, face stability was not guaranteed by means of the standard analytical methods. The design team was faced with a technically not feasible TBM passage. Therefore, advanced 3D numerical simulations were used to develop the TBM process parameters, making the passage technically feasible and to design the mitigating measures. Advanced monitoring results of excess pore pressures originating from the TBM face of the deeper Western tunnel were integrated in the 3D FE models for the Eastern tunnel. The paper describes the comparison between the analytical methods and 3D numerical simulations of the face stability, the results of the excess pore pressure measurements and the settlement performance of the TBM.
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