Johnson St Bridge

Project Overview:

Installation of 4’ – 6’ Ø Piling / Caissons for the Johnsons Street Bridge and Promenade Retaining Wall

Project is a design build based on indicative tender documents. The Bascule pier is supported on 1830mm Ø x 25mm wall casings up to 33m long installed through 18m of overburden and seated into 340mPa granite rock. A 7m deep open rock socket was completed below the casing tip. The bedrock profile is extremely undulating with grade differences of 2.2m across the diameter of the casings. Pipe piles were fabricated on site with cutting teeth installed on the tips. The 44 ton pipes were passed off to the 160 ton crane positioned on the work platform installed at the pier location. The cut-off elevation of the pier piles is 3m below low water. A specially designed reinforcing cage suspension bracket was utilized to support the reinforcing cage splicing and support during the concrete pour. All concrete was 45 mPa and tremie poured.

A Leffer LKG1-180 Spherical grab was employed to excavate the overburden and dumped directly into trucks for disposal

A Wirth PBA 612 Pile Top drill was utilized to seat the steel casing into bedrock and complete the 7m deep sockets. This is a reverse-flood drilling system with a closed loop discharge of the tailings into containment tanks. The tailings dropped out of suspension and the water was recycled back into the pile.

Installation accuracy during the pile installation was critical due to the installation method for the pier substructure. All piles were installed within 35mm of design position and within 0.5 degree of vertical.

The rest pier, intermediate pier and east abutment are supported on 1220mm diameter x 19mm wall piles drilled through overburden, seated into bedrock and completed with a 3-5m rock socket.  Reinforcing cages and tremie concrete completed each pile.

The 1220 diameter piles were installed with a Nissha RT150 rotator and Down-hole Hammer reverse-circulation drilling system. Tailings were dumped into water proof bins through the closed loop system. The rock sockets installed were reinforced as shown on the drawings.

Each pile was flushed with fresh water until clear and a complete video inspection was complete before permission

Project Details:

Owner: City of Victoria
Client: PCL Civil Constructors Inc
Final Contract Value: $7,500,000
Duration: 2014

Project Logistics:

Drilled concrete piles – 1830mm Ø 16 Piles
Drilled concrete piles – 1220mm Ø 18 Piles
Drilled falsework piles – 610mm Ø 42 Piles

Services included in this project:

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