Stuttgart

S21 underground railway station

Foundation of the new underground station using around 2,000 Frankipiles NG®

The station’s foundations are largely determined by the loads from the cup-shaped columns, the external walls as well as other load-bearing components. The majority of the station structure, with its 28 cup-shaped columns, rests on cast-in-place concrete driven piles. The loads are transferred to the load-bearing soil layers via groups of piles.

Around 2,000 Frankipiles NG®

Around 2,000 Frankipiles NG® were manufactured for the foundation.

Technical specifications:Depending on the load requirements, structural piles were designed for characteristic loads of up to 4,900 kN.

• Number: approx. 2,000
• Diameter: 61 cm
• Length: approx. 12 m
• Operational loads: up to 8,000 kN

Pile groups for high loads

In areas subject to particularly high structural loads, pile groups comprising up to 24 or 37 driven piles were installed. These pile groups are located beneath the heavily loaded structural areas of the station and serve to transfer loads from the cup-shaped columns and trough walls.

Pile load tests

Before the start of the main construction work, pile load tests were carried out in a test area. During these tests, test piles were subjected to loads of up to 8,000 kN. The results served as the basis for the construction of the final foundation.

Frankipiles with expanded footings

The Frankipiles NG® were manufactured with a specifically designed expanded footing. By shaping the pile base in this way, the load-bearing capacity of the piles could be adapted to the respective load requirements. The work was carried out taking into account the site’s geotechnical conditions as well as water law regulations, which limited the permissible pile lengths.

Quality assurance during production

During production, the driving works were continuously documented. This included recording the driving energy applied and the number of blows. These data were used to monitor the execution and to document the foundation works.

Foundation for the new underground station

The installation of around 2,000 Frankipiles NG® laid the foundations for the new underground station in Stuttgart. The pile foundation forms the basis for the load transfer of the cup-shaped columns, external walls and other structural elements of the station.