BAB 100 - The project
The planning phase
The plans to extend Berlin's inner motorway ring from Tempelhof to Neukölln date back to the 1960s. They failed because of the considerable strain this stretch, which was planned as an open section at that time, would have placed on the neighbouring residential areas. In 1987 a decision was taken in favour of the shortest and most purpose-specific option: a 1.7 kilometre tunnel.
The reunification of the two halves of the city made the need for an east-west link even more pressing. The public works planning procedure was completed in September 1995. Building work began in November 1995. In July 2000 this section was released to public traffic.
The transport network
The tunnel in the district of Britz extends the existing western city ring to Buschkrugallee. A junction was built on Britzer Damm with two parallel ramps to and from Tempelhof. The tunnel ends at Buschkrugallee, an important arterial road in the Berlin transport network.
The next section of the motorway ring up to Grenzallee was finished in july 2004. On completion of the A 113 to the border of Berlin, the A 100 will connect up in the south-east, too, to the national motorway network.
In the forecasting horizon 2015, 170,000 vehicles will use this new section daily.
The urban landscape
65% or 1,713 metres of the 2,621 metre long section are underground. This was necessary in order to comply with the statutory provisions concerning compensation and substitution for intervention in nature and landscape without having to change the route. The tunnel in the district of Britz has led to a noticeable reduction in the volume of traffic on the surrounding roads.
In parallel, a new pedestrian and cycle path network has been created. Today, it provides a direct and safe link between Tempelhof and Neukölln: a steel arch bridge over the very busy Britzer Damm.
Execution
For the execution of this work the section was broken down into four sub-sections.
The first building section was a new access road from Gradestraße in a westerly direction. This bridge was built as a flyover and consists of two different types of structure. A 63 metre long half-timbered composite structure spans Teltow canal; the ten other bridge segments consist of trapezoidal, pre-stressed concrete box girders. The highly vibration-proof building methods protected the old buildings on nearby Gottlieb Dunkel Straße.
The second building section consisted of the westerly tunnel access road and the adjacent 274 metre-long section of the tunnel. Here (as in the third section) the excavation for the two three-lane tubes was reinforced with interpile sheeting. A latched ventilation structure was erected directly at the west portal.
The third building section extended from Hattenheimer Straße to the junction Britzer Damm. On Ellricher Straße an operating building was constructed with a rainwater pumping station.
As a consequence of the narrow building conditions and in order to protect the residents from building noise, the underground construction work on the fourth section of Britzer Damm up to Buschkrugallee was carried out under top cover. The walls of the tunnel were initially positioned with replacement type piles. The tunnel was then roofed and the earth was excavated. At the east portal on Rungiusstraße there is a second ventilation structure.
The two tunnel tubes are both 14.5 metres wide, 12.5 metres of which are used for the actual motorway: in each tube there are three 3.5 m wide lanes, a 1.5 m wide hard shoulder and two 1 m wide, elevated verges.
Throughout its entire length the tunnel is above the groundwater level. Hence, there was no need for complicated sealing or foundation work. Only the rainwater pumping station beneath the tunnel required extensive foundation and sealing work. For the 27 cm road surface up to 1,900 m of concrete were processed every day. In this way the concrete work on the entire road surface could be completed in just ten days. Concrete was used as the road material because, aside from its long service life, it also offers low maintenance costs, because the light surface in the tunnel requires less lighting and generates lower costs, because no grooves can be worn and because concrete is more fire-proof than asphalt.
Jet fan ventilators in the roof coves carry waste air to the two ventilation structures at the entrances to the tunnel. They emit the waste air at higher air levels and, in this way, dilute it to an environmentally compatible level.