S21, new S-Bahn line (2nd section, Berlin HBF - Potsdamer Platz)

DB Netz AG is planning a 2nd construction phase for the S21 urban railway in Berlin. The aim is to extend the S21 from the 1st construction phase to Potsdamer Platz.

The second construction phase connects the main station to the 1st section of the S21 and at the intersection of the Nordsüd-S-Bahn to the parking facility of the Potsdamer Platz station.

The challenges of the project lie particularly in the undercrossing of various buildings, the U5 and the Spree.

For the realisation of the 2nd BA, 9 different variants were examined for the preliminary planning. These different variants run partly parallel to each other or also as in the current favoured variant 7 left and right of the Reichstag building. The starting point and area of the end point of the route are defined. In all variants, the S-Bahn system is located in a tunnel.

It is planned to advance the tunnel by means of a TVM with hydro shield. Tubbings with a thickness of 45 cm will be installed. The tunnel runs over a distance of 863 or 800 m (east/west) and is to have an outside diameter of 7.46 m. The tunnel is to be built with a diameter of 7.46 m. The tunnel is to be constructed with a diameter of 800 m.

Geologically, fillings, Quaternary layers in the form of loose to dense sands, gravel and silt, clayey sandy silt and siltory/sandy clays as well as organic soils will be found in the route areas. Due to the Spree, the groundwater level is only a few metres below the ground level (approx. 3-5 m).

Region: Berlin
Tunnel use: Traffic: S-Bahn
Client: DB Netz AG
Planner: Obermeyer Planen und Beraten; IMM Maidl & Maidl Beratende Ingenieure GmbH & Co.KG. (Tunnelbautechnischer Berater), Baugrund Dresden (Geotechnischer Berater)
Construction method(s): trenchless (TBM)
Tunnel length: 863 m (east), 800 m (west)
Cross section: 43.7 m²
Costs: 196 million €