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Firing on all fronts

Construction of the first of two Crossrail tunnels below the Thames got underway last week with the launch of the first of the project’s slurry tunnel boring machines (TBMs). Mark Hansford updates on progress on the £14.5bn project.

Crossrail’s fifth tunnel boring machine began its 2.3km journey from Plumstead to North Woolwich last week as work beneath the Thames got going in earnest.

The 110m long Herrenknecht TBM - named Sophia - was launched from the Plumstead portal in Kent and is expected to progress at an average rate of 100m a week to North Woolwich.

The Thames section of Crossrail is the only part being excavated through Chalk, which is why slurry TBMs were selected for this part of the scheme in place of the earth pressure balance TBMs being used elsewhere. The soils excavated by Sophia will be pumped out as a liquid slurry to treatment plant at Plumstead where it will be separated into sand, gravel, water and chalk. The chalk will come out in “cakes” or slabs of filtered chalk particles.

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Plumstead portal

“The launch of Sophia demonstrates the great progress the project is making, stimulating the economy, generating thousands of jobs during construction and delivering huge transport improvements to people living in south east London,” said Crossrail minister Stephen Hammond at the launch.

Across the whole Crossrail project, eight tunnelling machines will construct 21km of twin tunnels under London. In total the Crossrail route will pass through 37 stations and run 118 km from Maidenhead and Heathrow in the west, to Shenfield and Abbey Wood in the east.

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Limmo Peninsula: Launch site for western running tunnels

New aerial images released by Crossrail give an early glimpse of this work. The images were released as Crossrail outlined its key delivery milestones for 2013 as the project moves into the peak of construction between now and 2015.

The aerial images show the progress and huge transformation at Crossrail sites in central and south east London including the Plumstead portal where Sophia and her sister Mary will drive the new 2.3km tunnel beneath the Thames.

Elsewhere, the images show flagship new Crossrail stations under construction in central London and Docklands, including the tightly constrained Bond Street station box.

The images also show the tunnelling sites on either side of the capital where four huge tunnelling machines were launched in 2012. Over 3km of tunnel has been constructed to date.

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Bond Street: Station box excavation work is underway

Limmo Peninsula is the eastern tunnels logistics site (bottom right). Elizabeth and Victoria, the third and forth tunnelling machines, were lowered into huge 40m deep access shafts and launched towards the end of 2012. They will each travel 8.3km each westbound towards Farringdon.

Click here to see all the images

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