Great Belt Tunnel: Cross passage construction

The Great Belt Tunnel, connecting the two Danish islands of Zealand and Funen, consists of two single track bored tubes, each 7.400 m long, connected each 250 m with Cross Passages. The tunnel alignment crosses glacial tills and tertiary marls down to 75 m below the surface of the Great Belt. The Cross Passages thus are constructed in a wide variety of ground and groundwater conditions. The Cross Passage works include extensive soil investigations and ground treatment. The ground treatment methods include vacuum dewatering, microfine cement grouting, spiling, electro-osmosis and ground freezing. The Cross Passages are excavated by coventional hand methods using both traditional timbering and shotcrete with steel ribs as support. They are lined with hand-built 4.5 m i.d. SGI segments. Elaborate steel propping frames are used to support the Main Tunnels during excavations.