FOUNDATION CONTRACTOR Roger Bullivant recently finished driven piling for the £56M Odyssey Millennium project in Belfast.
The site, on reclaimed land at Queens Quay and adjacent Abercorn Basin on the east bank of the River Lagan, was once part of the Harland & Wolff shipyard. The Odyssey project, which comprises a 12,000 seat covered sports arena, retail development, cinema and Ulster museum's science centre is due to be completed in 2000.
Bullivant started installing 2,475 precast concrete piles (around 55,000m) at the end of October 1998 as part of a £1.2M contract for client Odyssey Trust and main joint venture contractors Farrans Construction and Gilbert Ash NJ.
The main challenge for the project team was the ground conditions. Unlike most of Belfast, which is underlain by soft alluvial deposits (known locally as Sleech) overlying boulder clay with dense sand at depth, the Odyssey site has 5m of Sleech over a 5m to 6m thick sand layer on top of the boulder clay.
The density of the upper sand varies to such an extent that piles could not be founded in the layer with complete confidence, so after discussions with consultants Kirk McClure and Oscar Faber, it was decided to be drive through the upper sand and into the dense sand layers below the clay.
The 300mm square precast concrete piles of 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, although some were in groups of up to 12. Some of the grouped piles needed pre- drilling 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. These were made at a new Bullivant factory in County Armagh, which proved more cost effective than shipping from the company's factory at Drakelow 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.