Construction method - tunnelling
The 2,082-metre Osterberg Tunnel, which has two single-track tubes, is being constructed as a double-skin vault structure with an outer skin of shotcrete and a concrete vault inner skin by conventional means using explosives and excavators. The two skins are separated by an air cushion foil.
The tunnel cross-section is being excavated in sections: the upper section first followed by the two lower sections. The cross-passages are started soon after the upper section is excavated so as to keep the tunnel logistics for the excavation of the lower sections separate by crossing between the two tubes.