The TBMs rwill be up to 120m long and weigh around 850 tonnes. Manufacturing is set to get under way shortly. Herrenknecht will deliver two TBMs to Royal Oak Portal for the western running tunnels in early 2012, two TBMs to Limmo Peninsula for the eastern running tunnels in mid 2012 and a further two machines to Stepney Green later in 2012.
Construction of the 21km of 6m-diameter twin-bored tunnel will require at least seven TBMs for the 10 individual drives. Consideration is currently being given to the need for a further TBM on the short tunnel drive between Limmo Peninsula and Victoria Dock Portal. The construction method for this section is the subject of ongoing discussions with the tunnelling contractor.
Herrenknecht has been selected as manufacturer by Crossrail’s tunnelling contractors. There are no UK-based TBM manufacturers. As the Thames Tunnel construction contract has only recently been awarded, the TBM manufacturer for this tunnel drive will be announced later this year.
There will be two different types of TBM to reflect the differing ground conditions along the Crossrail route. All of the tunnel boring machines, except for the TBM used to construct the Thames Tunnel, will be earth pressure balance machines. These will pass through ground which is predominantly London clay, sand and gravels. The Thames Tunnel, which is predominantly constructed through chalk, will use a slurry TBM.
The TBMs will run nearly 24 hours a day, 7 days a week, 365 days a year. Each TBM will be operated by a ‘tunnel gang’ of about 20 people - 12 people on the TBM itself and eight people from working from the rear of the machine to above ground.
As the TBMs advance forward, precast concrete segments will be built in rings behind the TBMs. Crossrail has also confirmed that the concrete segments for the western running tunnels between Royal Oak and Farringdon will be manufactured at Old Oak Common and transported to the TBM by rail. Crossrail is currently finalising arrangements with the tunnelling contractors for location of the other concrete segment manufacturing sites.
Construction continues to advance on the new Tunnelling & Underground Construction Academy in east London which has recently ‘topped out’. It will offer training to at least 3,500 people in underground construction alone over the life of the project.
Londoners will be given the chance to name the tunnel boring machines and will be able to follow their progress as they make their way under the capital via the Crossrail website. “In less than a year, the first tunnel boring machines will have arrived and begun their journey from Royal Oak to Farringdon,” said Crossrail chief executive Rob Holden. “I’m delighted that Londoners will be given the chance to name the machines that will build the major new rail tunnels under London. Even though the start of tunnelling is still about nine months away, work has been ongoing since early 2010 to construct the tunnel portal at Royal Oak from where the first TBM will launch.”
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