Driven precast pile production topped 1,000m/day on Belfast's Odssey project.
Belfast's £90M Odyssey project is the first major development on the east side of the River Lagan and is seen as a catalyst for further investment.
The project, which includes a £45M grant from the Millennium Commission, will provide a leisure, retail and science centre, Imax cinema, a multi- screen cinema complex and an indoor arena for ice hockey and rock concerts.
Ground conditions provided one of the main challenges to the project team. The site, on reclaimed land at Queens Quay and the adjacent Abercorn Basin, was once part of the Harland & Wolff shipyard.
Most of Belfast is underlain by soft alluvial deposits (known locally as Sleech) overlying boulder clay with dense sand at depth, but the Odyssey site has 5m of Sleech over a 5m to 6m thick sand layer on top of the boulder clay.
Density of the upper sand was found to vary so much that piles could not be founded in the layer with complete confidence. After discussions with consultants Kirk McClure and Oscar Faber, it was decided to drive through the upper sand and into the dense sand layers below the clay.
Piling contractor Bullivant installed 2,475 precast concrete piles (about 55,000m) at the end of 1998 as part of a £1.2M contract for main joint venture contractors Farrans Construction and Gilbert Ash NJ.
The 300mm square precast concrete piles, between 18m and 24m long, were installed by three of Bullivant's hydraulic drop hammer rigs. Piles were either single or in groups, generally of three to five, sometimes up to 12. Some of the grouped piles needed predrilling up to 12m through the upper sand, although the first two or three could usually just be driven.
The piles were made from 3m, 4m and 6m long precast segments connected by epoxy bonded joints. Bullivant established a new factory in County Armagh, which proved more cost effective than shipping from the company's Drakelow base in Staffordshire. Up to 1,000m of piles were delivered to site every day to keep up with the three rigs, with piling rate peaking at 4,500m a week.