27 February 2018
Brady Marine & Civil Grafton team recently completed the last bored pile on the marine portion of the new Grafton bridge project in Northern NSW. The NSW Government is funding this $240 million project which involves building an additional 525 metre bridge 70 metres downstream from the existing road and rail bridge. The Brady subcontract works include all five river piers and the installation of the associated 65T pre-cast skirts on the project, which is being delivered for Fulton Hogan and Roads and Maritime Services.
The three metre diameter bored piles are a crucial element in the bridge design, with only two piles per pier to support the 74m spans of the new crossing over the Clarence River. Reinforcement cages feature large diameter reinforcing bars (up to 40mm) and multiple layers (up to three with an inner rectangular cage), which required extensive attention to detail and quality control throughout the whole process of pile excavation, casing installation, and reinforcement to ensure tight construction tolerances were achieved.
To facilitate this complex operation our barge Maeve Anne was fitted with a bespoke pile gate and a BG40 drill rig mounted on the bow. Some piers required a ‘drive-drill-drive’ technique to achieve the requisite casing penetration into rock, a methodology that worked extremely well.
Concrete pours in excess of 150 m3 per pile were serviced by a smaller barge fitted with our 135t crane and a concrete placing boom, with concrete pumped from the shore along a floating delivery line.
The Brady team are now focussed on the blade pier construction, with piers up to nine metres high requiring a two-stage casting sequence using specially designed formwork. Subcontract works are expected to be completed towards the middle of the year.
To meet a number of specific project challenges associated with the technical specifications for such large elements while delivering the works as quickly as possible, the Brady team have also undertaken work outside of normal work hours.
Numerous high-risk heavy lifts have been required to complete the work. This has necessitated careful attention to lift studies, design, planning, coordination and implementation.