Important milestones in route construction: At the beginning of March 2016, the steel bridges for the tracks and the viewing platform in the direction of Elbe were lifted in the course of the new Elbbrücken stop. In August 2016, the structural work had already been completed at approx. 350 of 710 m planned tunnel length, i.e. about half of the planned length. All three structures (tunnel, trough and stop) extend over a total length of around 1.3 kilometres. The challenge for the specialists of the Max Bögl Group, responsible for the shell construction and special foundation engineering work, lies with regard to the logistics of the construction process in the spatially confined building area. The construction site, which is just 15 metres wide, is bounded to the north by an existing long-distance train line operated by Deutsche Bahn and to the south by development measures for HafenCity Hamburg.
Tunnels - Building below the groundwater table
The tunnel structure, divided into seven docks near the banks of the Elbe River, will be constructed over a length of 710 metres under the protection of a diaphragm wall shoring using an open construction method. Below the tunnel, the excavation pit was sealed with a 1.50 metre thick underwater base. This was anchored in the ground with around 1,000 micropiles and concreted dock by dock with the construction of the first base segment in February 2016 by divers. Diaphragm wall construction and diaphragm wall foundation elements were completed in October 2015. A special formwork carriage is used for the monolithic concreting of the tunnel elements, consisting of walls and slab. A tunnel element will be completed in weekly cycles. At the same time, individual wall and slab elements in parts of the building docks will also be produced separately with the aid of one-sided wall formwork and a slab table. By the end of August, 49 of 71 base elements and 40 of 71 tunnel elements had been completed.
Trough - a short above-ground section
The subsequent trough structure is subdivided into six blocks, each 40 metres long. It is predominantly constructed in a dry excavation pit secured by back-anchored sheet pile walls. The individual blocks are based on a total of 24 transverse diaphragm walls at a settlement depth of 19 metres. Parallel to the tunnel work, earthworks and diving work are currently being carried out in blocks 1 and 2, while the shell work has begun in block 3. In blocks 5 and 6, the area between the trough walls will be filled with filling concrete, and an emergency platform will also be erected in block 6. The construction period for the tunnel and trough is around 40 months and will end in July 2017. By the time it is completed, almost 120,000 cubic metres of concrete and 12,600 tonnes of reinforcing steel will have been installed. During this time, earth movements will have to be mastered in about 200,000 cubic meters.
Elbbrücken bus stop
The stop, designed by the renowned architects von Gerkan, Marg und Partner, adjoins the trough in the south and is to be completed simultaneously by the end of September 2016. By then, two technically sophisticated steel construction bridges with a total length of 40 metres each will have been completed. The steel bridge superstructures will be prefabricated in the company's own steel construction and transported by inland waterway vessels. Here, too, the construction site is limited to the area to be built on and is just as demanding as the complex foundation measures. 600 metres of large bored piles (D = 1,500 mm) with foot widening and an inclination of up to 22.5 degrees have to be installed. In addition, there are 2,240 metres of in-situ piles (D = 600 mm) and 3,900 metres of full displacement bored piles (D = 600 mm). Around 13,000 cubic metres of concrete are used. On the north side of the trough structure, two basements for technology and equipment will be integrated, which in turn will be based on a 1.20 metre thick pile head slab.