Cut & cover building pit
Alsterufer 1-3 Immobilen GmbH
APB. Architekten BDA
- 4-storey building pit in ground water
- Building pit category GK3
- Diaphragm wall, drilled pile wall, piles with I-beams inserted
- Top down construction method
- Pre-stressed steel framework, reinforced concrete partial cover
- Surface area: c. 80 x 80 m
- Depth: c. 13 m
- Time: 2012 - 2013
- Building costs: c. 9 mill.o EUR
- Our scope:
structural engineering of building pit and building
It starts in the earth.
It is principally its special location that makes an address first-class. But it must also be easily accessible. Therefore the new office location at Alsterufer includes parking spaces for nearly 400 cars. These don’t need to have any view of the Alster. So space was created in the basement. The building pit required for this was deep, and the challenges were correspondingly great: sensitive, protected neighbouring buildings, the waters of the Alster in the immediate vicinity. In addition there were a massive strong room and an air-raid bunker which needed to be broken up in the protection of the building pit. And all this with minimal permitted deformations in the building pit wall.
The solution: a diaphragm wall building pit with a partial cover. The bracing was performed in two layers. Above with a pre-stressed steel framework, because this is insensitive to possible damage from the heavy demolition works. Below with a reinforced concrete partial cover, the wide openings of which were closed in the course of the building shell construction and which thus served as the roof over the fourth basement storey.
Variant analyses supported by soil deformation calculations and soil-structure interaction investigations with our own programme BIN-GEO, developed in-house, led to the best technical and economic solution. The building work was additionally monitored by a complicated measurement programme which impressively confirmed the results of our complex advance calculations. Our building pit has fulfilled all expectations. Demolition, excavation and new construction could be carried out according to plan without any noticeable disturbance to the neighbours. It’s a real shame that it is no longer visible.