Hamburg
Construction pit for the ‘Six Friends’ housing project
Hamburg, Germany / 12.2016 - 07.2017
The “Sechs Freunde” housing development was built on a former railway site in Hamburg-Altona. The complex comprises six buildings, each with eight storeys, a total of 242 rental flats, four commercial units as well as a shared underground car park. A distinctive feature of the development are the so-called ‘crane buildings’, whose upper storeys cantilever out over the existing historic goods sheds. PORR special civil engineering was commissioned to construct the turnkey construction pit, including shoring, dewatering, soil excavation and anchoring works.
Facts & Figures
Company
PORR Spezialtiefbau GmbH
Type
Turnkey construction pits
Runtime
12.2016 - 07.2017
Turnkey construction pit for the crane structures
Construction pit for residential development and underground car park
The construction pit covered an area of around 5,200 m² and was excavated to a depth of approximately 8.50 m. The work was carried out in two phases to facilitate the subsequent structural work. The subsoil consisted of a heterogeneous sequence of layers comprising sandy fill, glacial clay, glacial marl as well as water-bearing fine and medium-grained sands. The groundwater was predominantly encountered below the planned base slab.
Diaphragm walls as a shoring and foundation element
A diaphragm wall, partly double-anchored, was constructed along the historic goods sheds. During the construction phase, the wall served as excavation shoring and, in its final state, also fulfils functions within the foundations of the cantilevered sections of the building. In total, approximately 5,750 m² of diaphragm walls were constructed, with a wall thickness of 60 cm and depths of up to 35 m.
Soldier pile shoring and temporary anchors
On the side of the excavation facing the road, a single-anchored soldier pile shoring wall was constructed. A total of around 2,040 m² of soldier pile shoring was constructed. To secure the construction pit, 312 temporary strand anchors with anchor lengths of up to 21 m were installed. The anchors were designed to withstand forces of up to 510 kN. Prior to installing the anchors and beams, the planned routes were surveyed to take account of existing structures and obstacles.
Soil Excavation and Dewatering
During the excavation of the construction pit, around 30,000 m³ of soil was excavated and removed. In addition, dewatering was carried out to secure the construction pit whilst the civil engineering works were in progress. The combination of diaphragm walls, soldier pile shoring, strand anchors and dewatering was tailored to the local subsoil and groundwater conditions.
Foundation for the crane structures in Hamburg-Altona
By excavating the construction pit, PORR special civil engineering laid the groundwork for the construction of the “Sechs Freunde” residential complex in Hamburg-Altona. The shoring and foundation works carried out form the basis for the underground car park as well as the cantilevered sections of the building above the historic goods sheds.
