Bachy Soletanche ExCeLs at marine piling

Leading geotechnical specialist conducts major marine piling contract at ExCeL London.

Bachy Soletanche Limited has taken to the water for its largest marine project in the firm's UK history for the construction of a marine deck at ExCeL London, the International Exhibition and Conference Centre.

The multi-million pound sub- contracted project is essential to the expansion plans of the Royal Victoria Dock based ExCeL London and will make it the largest exhibition and conference centre in the Capital.

The substantial extension is approximately half the size of the current building (Phase 1) and when construction works complete, it will cover an area equivalent to 14 football pitches.

Part of the extension, in line with Phase 1, will extend onto the constructed marine deck which hangs over the Royal Victoria Dock.

As the dock acts as a flood barrier for the River Thames and must stay unaltered, the marine deck is a necessary requirement to the project.

Main Contractor, Sir Robert McAlpine awarded Bachy Soletanche the 24 week marine deck sub-contract which includes the installation of 148no marine piles and associated decking work.

The pile installation will take place from both the quayside of the Royal Victoria Dock and onboard two barges.

85no piles will be installed from the quay and 63no from the barges.

The piles vary in diameter with 136no at 900mm diameters and the remaining 12no requiring diameters of 1050mm.

All are drilled to depths ranging between 34m to 44m; 2m to 10m of this is through water.

To construct the piles, 20m casings are vibrated into the ground with approximately 1.9m of the casing above water level.

The water within the casing is pumped out and replaced with Super Mud Polymer which acts as support fluid when piling begins.

Bachy Soletanche is using the large diameter rotary bore (LDA) technique to construct the piles within the permanent casings.

The cut-off level of piles is 200/300mm above the water level and equally spaced over six parallel rows.

The top of the pile is then broken down and replaced with a mortar top ready for the installation of 88no pre-cast beams.

These beams lay across the piles which are flanked by pre-cast concrete planks to form a solid base of the deck.

A topping slab will cover the initial base and the total decking area will cover 7,000m2.

In addition, Bachy Soletanche will cut holes in the existing, Phase 1 deck for the installation of 35no.

marine piles.

When these are in place, 200m2 of the original deck will be demolished and replaced by the new concrete quay.

The logistics of piling from the barges is one of the most challenging aspects of the project.

As such, getting the rigs onboard and keeping the barges stable during piling makes it a slow and delicate process.

Each barge is large enough to install 5no.

or 6no piles from one position so the first job is to anchor it using 'spuds' found at the back of the barge.

Specially built, in-house designed, movable 'gates' at the front of the barge, are used to hold the casings in place until they are vibrated into position.

Support boats, crawlers cranes and a service barge assist in the transportation of the rigs and provide access to the water's edge.

Once everything is in place (and when water is pumped out and polymer pumped into the casing), piling begins.

Ben Hardy, Bachy Soletanche Project Manager for the project commented: "There is a great deal of preparation time to consider, especially when piling from the barges, especially as it takes a day to install just one pile".

"The marine deck sub-contract therefore requires a great deal of forward planning, skill and perseverance from the Bachy Soletanche team".

Bachy Soletanche will complete the marine deck project at the end of January 2009.

The newly extended ExCeL London will be ready in time to play its central role in hosting seven Olympic and five Paralympics events at the London 2012 Olympics.

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