Bilfinger for Berlin rail

Two contracts for the expansion of the public transport system in Berlin, have been won by Bilfinger Berger - a new underground rail line in the centre of the German capital and a link between the main station and the urban rail ring.

The projects have a combined value of approximately €230 million, and the construction of the urban rail section will be carried out as part of a joint venture.

The urban rail line is described as one of the largest transport infrastructure projects in Berlin. The new U5 line will link the Alexanderplatz with the main station, and will connect the Brandenburg Gate to the existing section of the U55.

The project, on behalf of Berlin's transportation authority, comprises the construction of two tunnel tubes of approximately 1.6km in length, along with framework construction work for a track-switching system and two new stations.

The tunnel tubes will be built using the shield driving method which requires the use of a tunnel boring machine. The Museum Island station will be built using an underground excavation technique while the cut-and-cover method will be used for the construction of the Unter den Linden station.

The new stretch of the S 21, which will connect the main station to Berlin's ring line in a north-south direction, will be built by a joint venture under the leadership of German-based Bilfinger Berger, on behalf of Deutsche Bahn. A trough structure and several tunnel sections will use both the open construction and cut-and-cover methods.

One of the technical challenges for the project is that the sections near the main station will be built beneath girder grids and connected to existing excavation pits with the help of pressurised air.