Construction World July 2015

PORTS AND HARBOURS

Bay of Plenty PIER After a lengthy delay due to an appeal against the award, Franki Africa (KZN) was appointed by eThekweni Municipality in October 2013 to carry out the reconstruction of the Durban Bay of Plenty Pier and commenced work in March 2014. >

The main scope of works includes the demo- lition of 75 m of the existing piling and deck; installation of 22 no. 750 mm diameter x 24 m permanently cased piles; construc- tion of 75 m x 10 m wide new deck and the installation of 500 no. 4-ton geotextile scour protection bags within and around the seaward end of the pier. “The existing pier has continued to move due to the failed piles and in order to safely demolish the old pier and construct the new one, we have constructed a 110 m temporary jetty adjacent to the existing structure as a working plat- form,” Pearce says. The temporary jetty was completed in June 2014. Obstructions, including large boulders and concrete, below the sea bed have caused difficulties in installing piles and these had to be broken through using chisels and grabs resulting in lengthy delays. Where the existing failed piles obstructed the proposed new pile positions, the jetty has had to be redesigned to accommodate new pile positions. All piles have now been installed to depth, with one pile having to be installed at a rake. Ongoing settlement of the rock within the groyne and in the sea bed around the pier are causing the engineers some concern and additional scour protection measures are being taken to stabilise the situation and ensure the groyne serves its intended function of beach sediment control – and producing a decent, but safe, wave for the surfers. Reconstruction of the deck has started at the seaward end of the pier with the existing structure being cut into manageable pieces and removed to dump. The existing precast piles are being braced and incorpo- rated into a new capping beam below the new structure.

Franki engineer Paul Pearce says the existing pier is a reinforced concrete deck supported on precast concrete piles which retain a rock groyne beneath the pier. “Due to scour and failure of the precast piles, approxi- mately 75 m of the seaward end of the pier has failed and is to be demolished and recon- structed,” Pearce says.

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The new deck, which will be approximately 4 m wider than the existing deck, will be constructed in 11 sections. Custom shut- tering supported on the new and the existing piles is being used. The deck design and the formwork have had to be modified to accommodate the revised pile positions and the raked pile. As with all marine works, the risks associ- ated with rough sea conditions are ever- present making the fixing and maintaining of the deck shuttering challenging. One of the measures taken to speed up preparation works to avoid the exposure time is the use of glass fibre coated polystyrene blocks for soffits and void filling. Currently Franki’s Siva Govindasamy, a veteran Durban pier builder having worked on Dairy Beach Pier, uShaka Pier, Umhlanga Pier and the more recent Argyle Stormwater outlet, and James van Wyk are supervising the works. Due to the unforeseen ground condi- tions and associated delays, the works are currently behind schedule with contract completion scheduled for December 2015.

CONSTRUCTION WORLD JULY 2015