Pilot Project: Applying the Tunnel-in-Tunnel Method on DB electrified Routes

This report deals with the refurbishing of the Petersberg Tunnel. In this connection, for the first time within the scope of a pilot project, the tunnel-in-tunnel method was applied on an electrified line belonging to the DB. The tunnel cross-section was enlarged within the scope of the excavation. These activities were executed with the aid of a tunnel enlargement system (TES). Towards this end, the existing overhead line for electrification of the route had to be integrated in the excavation. Once the driving operations had been completed, the tunnel inner shell made of reinforced concrete was produced. Thanks to this project the spectrum of refurbishing tunnels has been considerably expanded, as the method can be deployed for other projects on the electrified route network.

1 Deploying the Tunnel-in-Tunnel Method

for Deutsche Bahn

The tunnel-in-tunnel method has already been successfully tried out and further developed on several non-electrified routes in regional transportation. In this method, the tunnel cross-section is expanded by drill+blast or cutting tools with trains services still operating and a new reinforced concrete inner shell installed according to the valid requirements of the code of practice. When construction starts, the track is relocated to the centre of the tunnel and services run in alternating directions for the duration of the scheme....

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