Geotechnical centrifuge tests to verify the long-term behaviour of a bored tunnel

Building the Rotterdam section of RandstadRail involves the construction of two bored singletrack tunnel tubes in the city area of Rotterdam, each with an outer diameter of 6.5 m and a length of 2.4 km. On several parts of the alignment the tunnel tubes are located at the transition of soft Holocene clay to stiff Pleistocene sand. It is expected that the top of the soft Holocene layers will settle 1.5 m due to consolidation and creep during the lifetime of the construction. Therefore the external loading on the tunnel lining will increase. The time dependent additional loading has been analyzed analytically as well as numerically. Physical modeling, using the Delft GeoCentrifuge, was performed in order to verify the design approach. The paper presents the results of the centrifuge tests and the findings of the back analysis using the finite element techniques.