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TBMs readied for Northern Line Extension

Northern Line Extension TBM

Construction of the tunnel boring machines (TBM) that will build the new Northern Line Extension tunnels is now complete.

Tunnelling for the project, which will extend the Northern Line from Kennington to Battersea via Nine Elms, is due to begin in early 2017 and is expected to take six months to complete.

Built by NFM Technologies in France, the 650t TBMs will now undergo factory testing to ensure all of the components are working correctly. Following testing, the machines will be dismantled and transported to London. On arrival in Battersea, reassembly of the TBMs is expected to take three months.

London mayor Boris Johnson said: “The construction of these mammoth machines is the clearest indicator yet that we are about to deliver the first major extension of the Tube in nearly 30 years. By extending the Northern Line, we are improving access to the Tube for thousands of south Londoners as well as triggering the creation of vital new homes and jobs.”

London Underground managing director Nick Brown added: “This is the first glimpse of the powerful machines that will help build the Northern Line Extension and bring Battersea and surrounding areas to within 15 minutes of the West End and City.

“The TBMs will make their way to London later this year and in early 2017 will start powering their way under south London to create the first major Tube extension since the Jubilee line in the late 1990s. Their manufacture is a significant step forward in the project which, once complete, will help us to support jobs, homes and growth in this area and keep pace with London’s rapidly rising population.”

The tunnelling scheme will involve excavation of 300,000t of material, which will be loaded onto barges and taken to Goshems Farm in Essex where it will be used to raise former landfill sites to create arable farmland. Transporting the excavated material by barge will remove the need for 40,000 lorry journeys across the city, which will contribute significantly to reducing the site’s carbon footprint.

TBM facts:

  • At over 100m long each, the machines are equivalent to the length of the pitch at Wembley Stadium
  • Each machine will undertake two individual tunnel drives to construct the 5.2m diameter tunnels
  • The TBMs, which will be named by local school children, will run 24 hours a day, seven days a week and will stop only for scheduled maintenance
  • As the machines progress, nearly 20,000 pre-cast concrete segments will be built in rings behind them.

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