Anabranch North and Southbound Bridge Repairs

Status: Completed March 2014

Location: Surfers Paradise, Gold Coast

Construct

Value: $5M + GST

Category: Civil / Bridges

Project Details

Gold Coast City Council contracted Alder Constructions to undertake a technically and logistically challenging civil engineering project. It is just the type of project the Alder Constructions excels in. The project consisted of the rehabilitation of bridge piles on 4 bridges under the Gold Coast Highway, 2 each way on the North and South end of Macintosh Island in the centre of Surfers Paradise. As well, installation of new rock armour to the banks of the channels and new footpaths and fences alongside these bridges were required.

Traffic disruption to this busy highway was not an option and works proceeded within the construction site of the light rail project as well as in the precinct of the GC600 car race. To make the project even more challenging were the site conditions – fast flowing tidal waters, limited head space due to the tides, embankments that could be destabilised if proper execution and monitoring were not continually adjusted and the discovery of a thick layer of rock at depth below the channel bed where sand had been expected – all handled adeptly and with imagination by the site crew ably assisted by our designers in Burchill VDM.

In total there were 56 piles that were showing signs of load stress and loss of durability. The possibility of future failure needed addressing.

The bridge rehabilitation involved upgrading the existing concrete piles from 457mm to 857mm in diameter. Steel liners were installed around the existing piles and driven to founding levels by means of purpose built hydraulic jacks and jetting equipment. 2 piles per bridge could be worked on at any one time and each casing required reinforced concrete installation after letting and jacking to required founding levels. Cleaning to founding level and crack repairs to the piles and 8 pier headstocks, specialist coatings to the piles and underside of existing walkways were also included in the works.

In addition, the embankments had to be stabilised and the abutments protected. Footpaths were also built under the bridges and along the channels. One of these was a “Tidal Immunity Footpath” requiring the floor of the footpath be built below the level of the high tides and excluding any water ingress.

Due to the technical nature of the repair, a specific methodology had to be developed and strictly followed to ensure short term slope and bridge stability. This also allowed project certification and ensured the long term structural integrity required.

The project was completed on time and on budget.

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