Tunnel de la Clusette – Shuttering Work in Safety Tunnel and Cross-Passages
After 50 years of operation, the 1km-long Tunnel de La Clusette on the H10 main road in the Swiss canton of Neuchâtel no longer meets the required safety standards. As part of the “H10 – Tunnel de La Clusette” project, it is therefore being renovated since 2021. In addition, a safety tunnel is being built parallel to the road tunnel so that it can be evacuated in the event of a fire. The project is due to be completed in 2026. The client is the République et Canton de Neuchâtel. Infra Tunnel, a Swiss construction company specialising in underground works, was awarded the contract to build the safety tunnel and the cross passages to the main tunnel.
Glass Fibre Reinforced Plastic Formwork Facing
A high quality concrete finish was required, so the choice of formwork facing played an important role in the project. In addition, a formwork panel had to be selected that could easily adapt to the shapes of the curved special formwork. The project managers therefore decided to use the glass-fibre reinforced alkus GM6 solid plastic panel for the formwork in the safety tunnel and also partly for the cross-passages. The 6 mm thick formwork facing from alkus AG in Liechtenstein is flexible but at the same time rigid and also meets high demands in terms of surface quality. Due to its robustness and durability, it also eliminates the need to change the formwork facing, which is particularly time-consuming in tunnels.
The alkus GM6 was used with the Rubrika tunnel carriage for the construction of the safety tunnel. The GM6 panel was riveted directly to the Rubrika formwork carriage on site and was not welded, but directly butt-jointed. Additionally, all the panels were riveted in a tight grid to prevent concrete from flowing in – which would have compromised the desired surface result.
Matte-Finish Formwork Panels for the Cross-Passages
A formwork system from Peri was used for the cross-passages between the main and safety tunnels as well as the emergency stop bays. At the initiative of the client and Infra Tunnel, the solid plastic GM6 formwork panels were also used where appropriate. A team from alkus AG supported Peri Switzerland at the Ohringen facility near Winterthur with the formwork: “We screwed the alkus panel to the Peri wooden construction formwork carriage, welded it and then matted it to achieve the perfect finish required for the concrete,” explains Michael Tschenett, Managing Director of alkus AG.
