Hydrostatic pressure-resistant sealing of tunnels in northern Bavaria, Germany
Location of work/project:
Germany - Coburg - Tunnels at Höhnberg and Füllbach
NAUE Sealing GmbH & Co. KG
For the tunnels near Coburg, Carbofol® tunnel liners were installed to ensure impermeability under hydrostatic pressure. Altogether 80,000 m² Secutex® protective nonwoven R 1001-B2, 80,000 m² Carbofol® tunnel liner 3 mm, 20,000 m² Carbofol® protective layer, 6,000 m Carbofol® waterstop SAA 600/6 and 190,000 Carbofol® discs were used.
As part of the Deutsche Einheit (German Unification) Traffic Project 8.1, the Deutsche Bahn Netz AG (German Railways) ordered the construction of the Höhnberg and Füllbach tunnels on the Coburg-South section of the new twin-track line between Ebensfeld and Erfurt. The two tunnels cross one another with a vertical offset of 16 m, which meant an enormous challenge for the tunnel design.
Environmental restrictions did not permit drained-tunnel constructions, so all-round liners, impermeable under hydrostatic pressure (IHP), were utilized for both. The all-round liner structure is as follows (outside to inside):
• NAUE Secutex® R 1001-B2 ≥ 900g/m²
• 3 mm Carbofol® tunnel liner, all-round
• Six-rib Carbofol® waterstops at the block joints.
• Carbofol® protection sheet 3 mm at base
The Secutex® nonwoven is placed on the shotcrete and protects the Carbofol® tunnel liner against mechanical damage. The protection nonwoven is attached using Carbofol® discs with proven predetermined breaking points. The 3 mm thick Carbofol® tunnel liner is the main component of the sealing system. It is installed as a single, tunnel-encompassing layer and is also fixed with Carbofol® discs with predetermined breaking points and resists hydrostatic pressure. A white, light-reflecting signal layer on the inner face of the liner ensures good light conditions for the work underground and allows effective visual checking of the entire installed surface.
Six-rib Carbofol® waterstops are welded on at the block joints, so that any damage is easier localized, seepage is avoided and the Carbofol® tunnel liner is protected from the head shuttering and the resultant concrete edge pressure.
On the tunnel invert, a 3 mm thick Carbofol® protection layer is also used to protect the tunnel liner. It is welded to the waterstops to eliminate any leakage during concreting. After this, the concrete inner lining (thickness of up to 60 cm) is installed.