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Crossrail: piling forward

Last week, political big shots gathered at Canary Wharf to witness the official start of construction works on Europe’s biggest construction project. Alexandra Wynne was there to find out how one of Britain’s biggest station boxes will be built.

More from: Piling on board

Crossrail reached its first major construction milestone last Friday when politicians and press gathered to witness the installation of the first tubular steel piles for the newly renamed Canary Wharf station.

Despite being on the drawing board for decades and suggestions that politicians were wavering in their support (News last week), this is the first substantial piece of construction to get underway. Its start signals the beginning of the £15.9bn mega rail project.

All eyes on Canary Wharf

The route will stretch 118km from Maidenhead and Heathrow in the west, through 21.5km of twin bored tunnels through central London, and on to Canary Wharf, Woolwich, Abbey Wood and Shenfield in the east.

Surveying and enabling works are already well underway at many locations along this route and the property acquisition process has also begun. And last weekend saw the closure of Charing Cross Road in London’s West End as plant was mobilised ready to tackle the demolition of buildings around Tottenham Court Road Underground station. This is being upgraded as part of London Underground improvement works and will also interface with a Crossrail station.

Crossrail fact file

Boris Johnson signals the start of piling

Boris Johnson sets off the klaxon signalling the start of piling

  • Developer: Canary Wharf Group
  • Main contractor and project manager: Canary Wharf Contractors (wholly owned subsidiary of CWG)
  • Structural and building services engineer: Arup
  • Preferred bidder for enabling and civils works: Expanded
  • Retail and rooftop park architect: Foster & Partners
  • Station architect: Tony Meadows & Associates
  • Executive architect: Adamson Associates
  • Rooftop park landscape designer: Gillespies

256m

Length of the cofferdam box for the new station

£500M

Total cost of building the station and fitting it out

 

But all eyes are now on Canary Wharf station − known as Isle of Dogs until last week when it was renamed by developer Canary Wharf Group which is putting £150M into its construction. It will be the first station to be complete along the route and is scheduled to be ready for handover to Crossrail by summer 2012.

At that point the station will comprise a watertight cofferdam in the North Dock of West India Quay, running along the northern edge of Canary Wharf.

Once complete it will be ready to welcome the tunnel boring machine that will be working its way westward from the Limmo Peninsula across the Thames to the east.

The first task

But first there is the task of creating the station box − a 256m long, 30m wide, six storey deep structure that will rise out of the water from the below the river bed.

Much of the work to prepare for the work to create the box cofferdam has already taken place. Canary Wharf Contractors − a wholly owned subsidiary of developer Canary Wharf Group − has been busy dewatering the lower aquifer around the site to create a drier underground environment to speed piling by two or three times. Building this tied cantilever cofferdam requires some heavy duty piling.

Two Giken silent piling rigs will work eastwards and westwards away from one another above the water along the north side of the box, rotating 1.2m diameter tubular steel piles down to 18.5m into the dock bed. Canary Wharf Contractors says this is the first time this machinery has done this kind of piling in the UK. Work is expected to be complete by October.

“The project is not just about anticipating future transport demand it is also about London catching up with the demand which is already there.”

George Iacobescu, Canary Wharf Group chief executive

Although already large in diameter, these piles − of which there will be just over 300 − will be beefed up further. A 35m deep concrete reinforced pile will be augered through the centre of the tubes and an additional 75, same diameter, tension piles will be installed down to 57m in a line parallel to these.

Once tied together with a pile cap and connected to the tubular piles with a tie bar they will provide additional anchoring against uplift.

When the northern edge of the cofferdam is complete, the tubular piles will continue along the shorter sides of the rectangular cofferdam. The fourth wall will be provided by an existing Canary Wharf cofferdam that will be added to with a secant piled wall.

More 1.2m diameter piles will support 30 plunge columns that will eventually be visible in the middle of the multi-level station and retail areas.

Once this has been done water will be pumped out of the watertight cofferdam and the lower levels of the station will be excavated in the dock bed. Each level of the station will be dug out starting with the dock bed level first. Concreting for each floor slab follows as the excavation progresses downward.

A headline-grabbing project

When complete, the station will be among Crossrail’s largest. To give an idea of scale, the cofferdam box will be 256m long, more than the height of Canary Wharf’s One Canada Square tower, which is the UK’s tallest building.

But the station is not aiming to grab the headlines on size alone. Architect Foster & Partners has designed four levels of retail topped off by a grand rooftop park scheme. This will be sheltered under ETFE cladding, designed to allow trees to break through as they grow and create a semi-outdoor feel.

“Today we have 93,000 people working here. In the future it is expected that this will more than double.”

George Iacobescu, Canary Wharf Group chief executive

And many see Canary Wharf station as a beacon of hope in tough times as it is expected to generate more demand for space in the massive east London development. “It’s true that times are hard right now but Canary Wharf still expects to see growth return long before Crossrail is completed,” says Canary Wharf Group chief executive George Iacobescu.

“Today we have 93,000 people working here. In the future it is expected that this will more than double. So the project is not just about anticipating future transport demand it is also about London catching up with the demand which is already there.”

Crossrail timeline

Canary Wharf station when it is completed

The completed Canary Wharf station

Timeline for start of tunnelling and main construction for Crossrail at key stations:

  • May 2009 Construction at Canary Wharf station begins
  • Early 2010 Construction at Tottenham Court Road (east) begins
  • Mid 2010 Construction at Bond Street begins
  • Late 2010 Construction at Woolwich begins
  • Early 2011 Construction at Farringdon, Paddington and Whitechapel begins
  • Mid 2011 Construction at Tottenham Court Road (west) begins
  • Late 2011 Construction at Liverpool Street begins; Tunnelling starts from Royal Oak in west London and Limmo Peninsula in east London aiming to meet at Farringdon
  • Mid 2012 Tunnelling from Plumstead to North Greenwich begins
  • August 2012 Tunnel boring machine due to reach Canary Wharf
  • Late 2012 Construction at Custom House, just east of Canary Wharf
  • Mid 2013 Tunnelling from Pudding Mill Lane to Stepney Green in east London
  • Late 2014 Tunnelling from Limmo Peninsula to Custom House begins

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