The Berliner Stadtring, or Berlin city ring, is a part of contemporary Berlin history. It was planned as a ring road, but the Berlin Wall prevented the project from ever reaching completion. The first construction stage, between Kurfürstendamm and Hohenzollerndamm, was completed in 1958. Compared to these relatively peaceful times, the volume of traffic in Berlin has since increased more than tenfold. The Berliner Stadtring, officially known as the BAB 100, is now one of the busiest motorways in Germany and one of Berlin's central traffic arteries.
Improving links to the eastern districts
The BAB 100 runs in a southwestern arc, passing through the districts of Mitte, Charlottenburg-Wilmersdorf and Tempelhof-Schöneberg to Neukölln. The 16th construction stage comprises a 3170m long stretch from the Neukölln interchange to the junction at Treptower Park. It is scheduled for completion in 2024 and will improve connections between the districts in the east and the city ring, the A113 motorway and Berlin-Brandenburg Airport. Traffic experts predict that this will lead to a significant reduction in the amount of transit traffic in the south-eastern part of the city centre. Deep-level construction is one of the most important means of reducing noise pollution. However, the high groundwater level in Berlin and the tricky soil conditions mean that it also requires specialist civil engineering expertise – a prime case for PORR's teams of experts who possess specialist knowledge along the entire construction value chain.
High standards for a deep-level civil engineering project
The civil engineering works for the tunnels, troughs and bridges to be constructed in the 16th construction stage were divided into seven lots. Lot 6, the "Circle Line Railway Overpass", is 225m long. PORR is working with its subsidiary Stump-Franki Spezialtiefbau GmbH, which specialises in complex civil engineering projects to construct the trough for this lot, as it did for Lot 5.
Constructing the trough with an underwater concrete base
The challenges of the project are not confined to the actual engineering work – the inner city location with its high density of buildings and heavy traffic means that setting up the construction site facilities and the excavation and removal of more than 80,000 m3 of soil are also highly complex tasks.
As the trough blocks are below the groundwater level in several places, the construction pits have to be constructed with a horizontal underwater concrete base to make them watertight. A total of 9,800m3 of diaphragm walls measuring up to 1.40 metres in thickness and up to 30 metres in height, 7,100 metres of grouted anchors, and 10,300 metres of tension piles are used as tie-backs and to provide lateral support.
