OVER 2,000 sheet piles have been used to create the new river frontage at the Millennium Stadium in Cardiff, the new home of Welsh Rugby.
The high-yield steel sheet piles were supplied by Corus, the new international metals group formed by British Steel and Dutch firm Koninklijke Hoogovens. They were installed to support the 900m long cantilevered walkway that runs along the riverside edge of the new stadium.
Built by main contractor Taylor Woodrow, the Millennium Walk extends up to 5m out over the River Taff, providing access for vehicles and emergency services.
Redditch-based foundation contractor Mining & Piling used two crane mounted vibro hammers to drive the Larssen LX32 and Larssen 6 high grade steel piles through sandy gravel, clay with cobbles and into the underlying Mercia Mudstone. Where ground conditions were particularly tough, the firm used a 2t hydraulic drop hammer to drive the piles.
Consultant WS Atkins specified the special heavy-gauge high-yield steel piles because the significant overhang of the walkway means the piles have to withstand complex turning moments and must perform both retaining and bearing functions. The piles could not be tied back in places, so a thin wall pile structure was installed, forming a 'mini-cofferdam' where the two walls were tied together.
Surrounded by office buildings, the site was noise-sensitive but because of the hard bedrock, silent piling methods could not be used. Instead, Mining & Piling developed a shroud to fit over the drop hammer and used modified piling gates on the vibro hammers to reduce noise levels and allow longer working hours.