The Berliner Verkehrsbetriebe (BVG) are extending the U5 Metro from Alexanderplatz passing the Berlin Rathaus directly through Berlin’s historic centre to reach the Brandenburg Gate. It will link up there with the already completed U55, which runs to the Berlin Hauptbahnhof via the Bundestag Station. After the U6 extension is finished, there will be a direct connection to the historic city centre, the government district and Berlin Hauptbahnhof without having to change. The Red Rathaus, Nikolai District and the Museum Island can finally be reached by Underground. The outcome will be new connections linking up with the Berlin rapid transit and bus network for around 155,000 passengers per day.
The 2.2 km long new route (€ 433 million) will possess 2 single-track bores and 3 new stations: Berlin Rathaus, Museuminsel and Unter der Linden. The 2 roughly 1.6 km long bores are to be driven one after the other using a 74 m long Mixshield (S-788, Herrenknecht AG) with 6.67 m diameter weighing 700 t by mid-2014 at a depth of 5 to 17 m and lined with reinforced concrete segments, comprising 1.40 m wide and 0.35 m thick rings made up of 6 equally large segments and a keystone (6+1). After approval at the Schwanau plant near Offenburg, the Mixshield was dismantled and transported to Berlin by waterway. After being reassembled in the 20 m deep starting pit at Max-Engels-Forum, the first bore was driven. The excavated material (some 120,000 m³) was carried via a conveyor belt to the starting pit and then removed via waterway.
The Unter der Linden Station transferring to the U6 is being set up by cut-and-cover; the Berlin Rathaus Station by the top cover method. The Museuminsel Station is being produced by trenchless means, as it is partly located beneath the River Spree. Here freezing is being applied as was the case with the Brandenburg Gate Metro station.⇥G.B.