Cross-passages in the TBM-tunnels of the Follobanen Project - design under high water pressures in hard rock.
A major part of the Follobanen railway tunnel are the twin-tubes of 19 km length, excavated with TBMs almost entirely in hard gneisses. Along the segmentally lined tunnels, 80 openings are foreseen for cross-connections. Their maximum overburden is 150 m with potentially almost the same water level. The openings in the lining are 3.8 m wide and 4.55 m high.In case of high water levels, grouting reduces the pressures during construction. For optimization purposes the pressures acting on the lining are assessed with 2D and 3D numerical analyses. Yet the high loading challenges conventional solutions for the lining. A number of measures are necessary to achieve structural integrity. These range from shear connectors to high strength concrete, but also extensive structural 3D-FE-modelling and stretched engineering thinking to assess and verify the actual behaviour of the structural elements.Design, Finite-Element-analysis, TBM-tunnel, shear-elements, Follobanen.