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Stump-Franki is winning sustainability points in NeckarPark

An urban development is currently in progress on what used to be the Bad Cannstatt freight station in Stuttgart. The NeckarPark site is a model project for sustainable building in the city – and building Q8 is no exception to the scheme: green roofs and greened clinker brick facades are among the various features ensuring a healthy microclimate. The 22-hectare development, which will offer a mixture of homes, jobs and shopping facilities, is to have its own park and a ‘Kulturinsel’ where artists of all types will meet, interact and create. Beneath the site run mineral waters, prized for their healing properties. These must be protected from environmental influences in all circumstances. Stump-Franki in Stuttgart was contracted by Wolff & Müller Hoch- und Industriebau to install the environmentally friendly pile foundation and a watertight soft gel floor slab.

© Stump-Franki

Almost everyone has heard of the Cannstatter Wasen, the world’s second-biggest folk festival. The Mercedes-Benz Arena and the Hanns-Martin-Schleyer-Halle are likewise familiar names far beyond the city boundaries. But did you know that Bad Cannstatt – which merged with Stuttgart in 1905 – has also been dubbed a spa town? In fact, with 44 million litres of mineral water flowing daily from 19 springs, Bad Cannstatt is second in Europe only to Budapest by volume. The majority of these springs have been officially recognised as ‘Heilquellen’ – in other words, the water has health benefits. Such Heilquellen are legally protected by a heritage regulation established in 2002, so the planners for the NeckarPark development had to ensure the construction methods would not interfere with the groundwater in any way. It was time to call in the civil engineering experts at Stump-Franki in Stuttgart!

IMG 4724 Bohrung für Weichgelinjektion

Groundwater protection with environmentally friendly Frankipfahl NG® piles

Length restrictions apply to the piles for the zone around the mineral waters. The water-bearing strata are covered by a protective stratum of gypsum Keuper. The challenge for the Stump-Franki team was to transfer loads to the subsoil while keeping the piles as short as possible. The 351 Frankipfahl NG® piles used have an enlarged base, which means that even with shorter lengths they can achieve the same load transfer as other pile systems, and thus do not affect the gypsum Keuper stratum.

IMG 4993 Frankipfahl NG Maßarbeit in der Baugrubenecke

Soft gel floor slab with optimised carbon footprint

Several sheet-pile structures in the construction pit had to be protected from vertically rising groundwater, which meant a waterproof floor slab was required. Project manager Peter Deutsch explains: “We advised the client to use a soft gel injection-grouted slab instead of the planned jet-grouted floor slab – and were awarded the contract to do just that.” This technique has an excellent carbon footprint, since it uses much less concrete and requires much less transport. In addition, no grout material flows back from the process.