Segmental lining design for the crossing of a railway embankment in soft ground with very low overburden
In the southwest of the Netherlands the Sluiskiltunnel is currently under construction. It consists of two machine driven tunnel tubes with an outer diameter of 11 m. At the end of the alignment a 7 m high railway embankment is crossed with an overburden of 9 m. At this location the tunnel is excavated in soft clays and sands, with a peat layer of 50 cm in the tunnel face. Analyses are performed with a 3D-FEM-model incorporating the ground and four segmental rings, coupled in the ring-joint by friction and a cam and pocket-system. The rotational behavior in the longitudinal joints is modeled individually depending on the respective normal force in the joint. In addition to regular load cases, the decisive loads of freight trains on the embankment, flooding, fire in the tunnel and the situation after a fire are analyzed. The resulting required reinforcement is extremely high and realized with a fully welded reinforcement cage of 207 kg/m³.