Construction has begun on the 7.3km long Irlahüll Rail Tunnel that forms part of the $346.7m central section of the new 89km long Nuremburg- Ingolstadt high-speed rail link. The central section comprises three tunnels and seven bridges.
Hochtief will construct all three tunnels using drill+blast and the NATM. Each advance step will be 2-3m, also depending on the nature of the ground. Reinforcement with lattice girders and shotcrete will follow immediately and then a lining of in- situ reinforced concrete with wire mesh will be applied. Wheeled loaders will load the excavated material on to dumpers for transport out of the tunnel.
The Irlahüll Tunnel route lies generally in white Jurassic rock passing from north to south first through Oxfordian limestone and marlstone and then, for a length of 5.5km, through Kimmeridgian limestone and dolomite. Here, there is a pronounced irregular karst structure, which varies from karst with holes and fissures up to filled or open cavities. Intensive safety precautions will be taken in this area.
From the north, the alignment will proceed in groundwater for about 2.5km, entering a powerful groundwater aquifer in the mountain area.
Work on the 18.4 km central section, of which the Irlahüll Tunnel forms part, started in September 1998 after Deutsche Bahn, the German national railway administrator, awarded the contract for this section to Hochtief. Construction is due for completion by early 2003.
