Installing tunnels when tracks/roads are taken out of service

With this process, a tunnel is built in a traditional way beside a track bed or road bed. When the track or road is taken out of service the tunnel is moved to its definitive location. A number of tasks must be carried out before this can be done.

Den Bosch I
Leersum 1
Den Bosch II


First of all, sliding beams are positioned next to the tunnel. These are heavy steel profiles − for example, a double HE800B on which under-saddles are mounted, which are stainless steel strips that shape the sliding surface to the bottom. Trestles are then attached to the tunnel, which rest on the sliding beams by means of a screw-jack structure.

The screw-jack structure ensures that the tunnel can be pulled free of its base. The under-saddle is well greased to reduce any abrasion. Between the screw-jack structure and the under-saddle, a sheet of plastic is positioned with a very low friction coefficient and a high compressive strength. After the sliding beams are expanded once the tunnel has been taken out of service, the tunnel is moved with extendable screw-jacks. These are telescopic screw-jacks that attach themselves by means of a tail structure to a pattern of holes in the spiral chute. After reaching the definitive location, the deck is lowered and the extendable screw-jacks and screw-jack structures are removed. Then the track bed or road bed is repaired and put back into service.