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Crossrail tunnelling in southeast London gets underway

By Nick Mann

Crossrail tunnelling in southeast London gets underway

Sophia, Crossrail’s fifth tunnelling machine, today began construction of a tunnel under the River Thames for London’s new rail link.

  • Crossrail’s tunnelling machine Sophia gets going as work starts on newest rail tunnel under the Thames

  • Machine specially equipped to deal with chalk and flint ground conditions in southeast London

  • Crossrail will cut journey times to central London by up to 20 minutes for local residents

Sophia, Crossrail’s fifth tunnelling machine, today began her journey from Plumstead to North Woolwich as part of the construction of a tunnel under the River Thames for London’s new rail link.

The 110 metre long machine is scheduled to drill at an average rate of around 100 metres a week, installing precast concrete segments as rings to form the tunnel lining as it advances forwards.

When Crossrail opens, up to 12 trains per hour during the peak will link southeast London and the Royal Docks with Canary Wharf, central London and beyond – and will enable local residents to get to and from London’s key employment areas much more quickly and easily.

Passengers in southeast London will benefit from some of Crossrail’s most significant time savings. With Crossrail, the journey from Abbey Wood to Bond Street will be around 20 minutes quicker and passengers travelling to Heathrow will be able to shave around 40 minutes off their journey.

Sophia is different to the tunnelling machines being used elsewhere on Crossrail. Known as a ‘slurry’ machine, she is specially equipped to deal with the chalk, flint and wet ground conditions that she will encounter in southeast London.

As part of the tunnelling process, the excavated soils will be pumped out as liquid slurry to a special site treatment plant at Plumstead. The slurry will be separated into sand, gravel, water and chalk. The chalk will come out in ‘cakes’ or slabs of filtered chalk particles.

Stephen Hammond, Crossrail Minister said: “The launch of Sophia, Crossrail’s fifth tunnelling machine, 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 southeast London”

Andrew Wolstenholme, Crossrail’s Chief Executive said: “The start of tunnelling in southeast London marks another milestone for Crossrail, a project that will transform public transport in and around the capital. The benefits for southeast London are huge - for the first time people living between Abbey Wood and the Royal Docks will be able to travel right through the centre of the capital without having to change trains, bringing Canary Wharf, the West End and Heathrow closer than ever before.”

Across the whole Crossrail project, eight tunnelling machines will construct 21 kilometres (13 miles) of twin tunnels under London. The Crossrail route will pass through 37 stations and run 118 km (73 miles) from Maidenhead and Heathrow in the west, to Shenfield and Abbey Wood in the east.

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Ends

For further information contact the Crossrail Press Office on 020 3229 9552 or email pressoffice@crossrail.co.uk

Notes to editors:

  • Sophia weighs 1,000 tonnes and is 110m long, the equivalent of 11 London buses end to end. Crossrail’s slurry TBMs are shorter than the 150m long Earth Pressure Balanced tunnelling machines used elsewhere on Crossrail.
  • Sophia and Mary will excavate over half a million tonnes of material.
  • She will have 20 person ‘tunnel gangs’ working in shifts - 12 on the TBM itself and eight working between the rear of the machine to the tunnel entrance.
  • The diameter of her cutter head is 7.1 metres. Once tunnelling is fully up and running Sophia is scheduled to progress at an average rate of around 100 metres every week.
  • Sophia is named after the wife of Marc Isambard Brunel who built the first tunnel under the Thames. 
  • Sophia has a rotating cutter head at the front, and a series of trailers behind housing all the mechanical and electrical equipment. As the machine advances forwards, precast concrete segments are put in place to form concrete rings to line the tunnels. The segments are positioned with millimetre precision and held in place by hydraulic rams. Once the segments form a complete ring, the structure is extremely strong and stable. In the final stage of the process, adjacent rings are bolted together.
  • Unlike the Crossing tunnelling machines being used north of the Thames, Sophia needs to be able to deal with the chalk and flint that is found south of the River Thames. She has a sealed, pressurised, air-locked chamber behind the cutter head where the excavated soil is mixed with bentonite (a mixture of clay and water) to form a liquid. This slurry liquid is removed from the tunnel through a system of slurry tubes to the bespoke treatment plant located on site.

About Crossrail tunnelling

  • Sophia’s sister machine, Mary, is scheduled to start tunneling in mid-2013, and will construct a second tunnel alongside the first.
  • Joint Venture Hochtief Murhpy is constructing the southeastern tunnels between Plumstead and North Woolwich.
  • The first two machines Phyllis and Ada were launched in May and August 2012 and are now tunnelling their way from Royal Oak in west London, via Paddington, Bond Street and Tottenham Court Road, to Farringdon.
  • The third and fourth machines Elizabeth and Victoria were launched in December at Limmo Peninsula, next to Canning Town and will tunnel beneath the River Lea and through the new station box at Canary Wharf on their way towards central London.

Examples of journey time savings from southeast London

Abbey Wood to:

Station

Crossrail journey time

Time saving on current journey

Canary Wharf 

11 min

20 min

Bond Street

25 min

19 min

Heathrow

51 min

42 min