Germany’s highway vision

The Verkehrsprojekt Deutsche Einheit (VDE) is a building program that aims to bring East German roads up to the standards of the west. So far 11 000 km of roads have been built or rebuilt. Next year, $1,6 billion is allocated to road construction in the east. The government’s goal is to make the seven large motorway projects operational in significant parts by the turn of the century. These roads total 2000 km, of which 150 km is now usable and a further 440 km is already under construction.

The three road widening projects, from four to six lanes, are showing the most progress. Many sections are complete, and about 310 km is under construction including the A2/A10 Hannover-Berlin Ring, The A9 Berlin-Nuremberg and the A4 Eisenach-Dresden.

Marrying a sustainable environmental policy with widespread construction is another challenge the country faces. In western Germany, 440 km of new motorway was built, and 163 km was widened from four to six lanes. An additional 650 km of roads were also built, most of these being bypasses. These bypasses play a central role in the government’s environmental policy and a further 52000 km is planned. Just in the last year, 37 bypasses with a length of around 200 km have been built at a cost of $600 million. The government has also invested $3 billion to date in noise protection and has 2 000 km of noise barriers installed along roadsides.

Transport minister Matthias Wissmann says: “We can say this with pride: No country spends as much as we do on the environment and noise protection. That should stay that way!”

Reduced pollution is one of the benefits of intelligent transport systems (ITS), which the government is supporting, through its own economic forum. Wissmann sees the other opportunities that modern communication and information technology offers as being:

- better use of the available infrastructure, especially by increasing capacity at bottlenecks and smoothing the traffic flow;

- better coordination between the different modes of transport, spreading the burden equally;

- avoidance of unnecessary jams and unladed journeys, including motorists seeking parking spaces;

- improvement in safety.

The transport minister says that the intelligent transport industry has reached the stage now where close cooperation between transport policy makers and industry can significantly accelerate a widespread introduction of the technology.

Forming a tunnel

Europe’s most current important infrastructure project, a key element of the Oresund 16 km long bridge/tunnel link between Denmark and Sweden is the 3,7 km Drogden road tunnel.

This immersed tube structure will be the largest in the world, with the 42 m wide and 8,5 m high tunnel segments produced on land using the incremental launching methods, in use for the first time for a tunnel.

Production of the 20, 178 m-long elements making up the tunnel requires massive concrete placement and the use of formwork. Each of the tunnel elements is composed of eight 22,5 m-long segments, making a total of 160 tunnel segments, calling for 80 reuses per formwork assembly. The segments do not have any horizontal joints, and in view of the large number of segments and the need for top quality concrete, a method was needed that was based on factory prefabrication methods.

The segments were cast in a weekly cycle in a special plant in North Harbor, on the outskirts of Copenhagen. The requirements were stringent. Since the final position of the tunnel will be under the sea, the outer walls must be watertight.

The formwork must have only two levels of formwork ties in the wall height of 8,5 m and the holes must be watertight sealed. To achieve this the company is using the concrete cones bonding technique whereby the cones are bonded to the tie holes using a two component adhesive with granulate, which prevents the cones from setting during bond hardening.

A further challenge was the adaptability of the formwork to the changes in the cross-section of the tunnel geometry. The thickness of the tunnel bottom slab varies, as does the roof slab strength. However, the greatest difficulty is the alignment of the longitudinal incline of the tunnel segments. Some 50 different adjustments are required to the formwork in order that the entire tunnel profile is guaranteed.

Like the formwork of an incremental launching bridge, the base and external formwork is fixed. The inside formwork forms two motorway and two railway bores and one service gallery. Due to the monolithic construction, the inside formwork units must not be supported within the 22,5 m long segments, but suspended on giant lattice girders. These are supported outside the casting section. One lattice girder is 50 m long, 4m high and weighs 53 t. The total weight of the formwork assemblies is 2 300 t.

During the casting procedure, the entire dead weight of the segment and the dead weight of the inside formwork transfer to the bottom formwork. The load of about 7 500 t is distributed over 250 compression braces and conducted into the casting yard.

A casting procedure takes between 32 and 40 hours without interruption. After a segment has been cast and cured, bottom and outside forms are struck as in a bridge incremental launching plant, and the segment, together with the inside form, is then pushed forward one step on skidding beams.

Once the reinforcement — in this case a complete prefabricated reinforcement cage of 380 t dead weight — has been positioned for the next casting section, the inside formwork is retracted from the moved completed tunnel segment into the reinforcement and into the starting position for the next casting section.

The 50 m-long lattice girders serve as a “track” on which the inside formwork is hydraulically transported 22,5 m each time. This formwork procedure is repeated eight times, until a tunnel element of 178 m length is completed.