The Barangaroo site is a major extension to the Central Business District (CBD) of Sydney, and represents an increase of over 15 % in the size of the CBD. The southern portion of the Barangaroo site will be developed into three main office towers and several low-rise residential/office blocks, linked together with podiums and a common three-level basement. The bored piles are designed to carry the building loadings through rock shaft friction and end bearing. Groups of piles are designed beneath the raft cores with “mega piles” supporting the main tower columns carrying up to 10,000 t each.

The site has a number of challenges required to be overcome. The historic industrial nature of the site has meant that there is the presence of hazardous materials including asbestos in a number of areas. Piles in these areas are being installed in designated contaminated zones, requiring specialist personal protective equipment.

The 2.4 m diameter “mega piles” carrying the main tower columns are being installed under bentonite with a short temporary top casing. To improve drilling stability through the fill material the pile locations are being pre-treated with a bentonite-cement-silicate grout prior to pile excavation.