Marti Technik AG (Moosseedorf, Bern) drilled the Tunnels for the hydroelectric power station in Nant-de-Drance.

A special characteristic of the tunnel in Nant-de-Drance is the steep angle of its ascent.

The wagons had to be specially designed to handle the additional forces and strains.

For this big structure Marti Technik AG decided to task the Niederberger-Engineering AG with the technical design and calculations for the tunnelling wagons that follow the tunnelling drill.

A MOUNTAIN AS A CHALLENGE

The steel-wagons held the systems for reinforcing the tunnel walls, the band-conveyors for the excavation materials and all the supply-systems for air, water and electricity.

The waggons also are an emergency support for the drilling machine.

The waggons must stand extreme external conditions.

Non-stop vibrations by the colossal drill are strengthening the steel structure substantially.

Additional there could be a strong heat because of the machines and geothermal effects, damage through falling objects from the band conveyor and from the drill accelerated rocks .

Faulty operation by the personnel and accidents with heavy machinery were an issue that was concerned in the design.

Because the wagons can't be accessed inside the mountain and there is no space for doing repairs nor maintenance, the waggons have to be as robust as possible.

The calculations of strenght were very important because of the unusual circumstances and burdens.

Curves and an irregular ascent in the tunnel make it necessary that all wagons are connected with flexible elements.

Every wagon is connected to its directly preceding one and additionally is assured to.

The connections are realized with special tension elements.

The tunnel was completed in 2013 and the design by Niederberger-Engineering AG a full success.

For more information read the lowest article "concept for L1 and Trailer" on Tunnel-online.

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