Fremantle traffic bridge pile encapsulation

The scope of the work involved repairs to the timber piles to Bridge 0916 located over the Swan River on Queen Victoria Street.

Bridge 0916 was constructed in the 1930s and is one of the largest timber bridges in Western Australia. The existing timber piles supporting the 4 main piers in water depths of up to 12m had the existing concrete protection systems removed and a new reinforced concrete encapsulation installed. Protective wrapping was also required to the tops of the piles.

All work had to be carried out in difficult conditions – 12m deep water in strong currents. The Bridge has 2 busy navigational channels and vessels had to be managed throughout the Project.

The project included:

• Demolition of existing protection systems to pier piles. These existing systems were a combination of reinforced concrete, steel jackets filled with grout, fibreglass sleeves and wrapping. All of these systems needed different underwater techniques to remove.
• Cleaning timber piles and conducting measurements to confirm sizes.
• Wrapping piles with Superintendent approved corrosion protection tape system;
• Prefabrication of custom-made steel reinforcement cages and delivery to the riverbed;
• Installation of custom-made steel reinforcement at required cover around timber pile. This required a fixing system to be developed to ensure the cages were secure during concrete pours;
• Design and fabrication of a custom-made formwork system;
• Design and fabrication of concrete delivery valves and attachments to ensure concrete could be pumped into the formwork safely and without environmental issues;
• Installing approved formwork around precaged timber piles in 12m of water;
• Development of a self-compacting concrete mix that could be pumped effectively and flow around the timber to fill voids;
  and Pumping super-workable concrete in the annulus between the timber pile and the formwork;
• All of the above work was carried out by divers in difficult conditions.