The building boom in Berlin went even underground to ensure the transport network keeps pace with future demands. One of the projects on the North-South rail route is the "Berlin Central" main line tunnel, north of the main station (formerly "Lehrter Bahnhof") - under the River Spree and the government district as far as the Landwehr Canal. Of this, 740 meters run under the zoo and 500 meters from Potsdam Square to the Landwehr Canal. Berlin is built on difficult ground, composed of sand, loam and marl, which give the cutting wheel a really hard time.
The launch shaft is sunk right in front of the Reichstag. From here, two Mixshields set to work, gradually producing four parallel single-track tunnels with a total length of five kilometers. The tunnels are at depths of between 18 and 25 meters and entirely below the groundwater table at a depth of three to four meters. The TBMs are equipped with center knives to counteract clogging and with a stone crusher in the invert segment to handle, e.g., boulders.