CASE STUDY

40 ASR-Damaged Bridge Piles Encased Underwater in a Crocodile River

Under the Captain Cook Highway bridge over the Barron River estuary near Cairns, Queensland, all 40 prestressed piles in the four river piers were encased with seamless PileMedic® jackets and underwater grout. Divers worked inside steel cages, and the job took about five working weeks.

PRODUCT: PILEMEDIC®
APPLICATION: BRIDGE PILES
INDUSTRY: TRANSPORTATION

GET A PILE REPAIR CONSULTATION ALL PROJECTS

Workers in orange high-visibility shirts spreading epoxy on a long sheet of white laminate on a table under a bridge

40 prestressed concrete piles encased underwater

piles in four river piers: 40
working days on site: ~35
confinement vs. 300 psi required: 648 psi
minimum clear pile spacing: 12 in.

Project Details

OWNER: Queensland Department of Transport and Main Roads (DTMR)
LOCATION: Captain Cook Highway southbound bridge over the Barron River estuary, about 4.5 miles (7 km) north of Cairns, Queensland, Australia
STRUCTURE: 1977 bridge, 579 ft (176 m) long, seven 77 ft (23 m) spans; blade piers on pile caps, each on 10 octagonal prestressed concrete piles
DAMAGE: Alkali-silica reaction (ASR) cracking
QUAKEWRAP® SYSTEM: Two-ply PileMedic® laminate jackets, 25 in. diameter, filled with cementitious underwater grout
GENERAL CONTRACTOR: Roadtek (DTMR)
UNDERWATER CONTRACTOR: JD Marine
QUAKEWRAP® ROLE: QuakeWrap (Australia) provided training and technical advice to the divers
COMPLETED: 2015

PROJECT VIDEO

Repair of ASR-Contaminated Piles in a Crocodile-Infested River

Plays from YouTube

01 · THE CHALLENGE

Fifteen Years Looking for a Repair That Fit

In 2000, severe cracking was found in 13 of the 40 piles in the four river piers, and analysis traced it to ASR. DTMR chose encasement as the long-term treatment and set two criteria: at least 300 psi (2.1 MPa) of confinement to slow ASR, and a barrier against chlorides, moisture and oxygen.

The site ruled out the usual answers. Piles stand as close as 12 in. apart, too tight for individual concrete jackets, and the work had to be done underwater in a murky estuary with crocodiles, bull sharks and jellyfish. Concrete encasement estimates exceeded the funding, a 2003 FRP prototype could not hold fresh grout pressure, and seamed half-shell jackets were judged unsuitable. By 2014, 22 piles were cracked.

Concrete bridge blade pier on a wide pile cap at the water line, with the tops of piles visible just above the water

02 · THE SOLUTION

Seamless Jackets Built Around Each Pile, Underwater

In 2014, PileMedic® was identified as meeting DTMR's technical needs at around 40% of the previously tendered prices for concrete encasement, and it was approved as a trial installation. Roadtek undertook the work, with QuakeWrap (Australia) training the commercial divers and providing technical advice.

Each jacket was two plies of laminate around a 2 in. grout annulus, for a 25 in. diameter. The published design check gives about 648 psi (4.5 MPa) of confinement, more than double DTMR's 300 psi criterion.

Steel cage around each pier to protect the diving crew
4 ft wide laminate cut to 165 in. and coated with epoxy paste on the barge
Divers wrapped it over spacers and held it with ratchet straps while the epoxy cured underwater
First jacket set about 18 in. below the mud line, each next one lapped 4 in.
Annulus filled with cementitious underwater grout by tremie

Workers in orange shirts and hats lifting a curved white sheet of laminate over a steel mesh cage beside a concrete pier

03 · THE RESULT

All 40 Piles in About Five Working Weeks

The crew finished in around 35 working days in 2015. A typical pier took 1 day to install the protective cage, 4 days to wrap its 10 piles and place the grout, and 1 day to move to the next pier.

The final cost was A$0.95 million. The 2008 bid for concrete encasement was A$2.0 million, about A$2.46 million in 2015 dollars. Our Learn article on this bridge covers the full cost comparison, the 15-year timeline and the worked confinement check.

piles encased: 40
piers: 4
working days: ~35
final cost: A$0.95M