15.03.16
TBMs for Northern Line extension all set for testing
The two new 650-tonne tunnel boring machines (TBMs) that will build the Northern Line extension under south London have finished being built.
Transport for London (TfL) said the new machines, built by NFM Technologies in Le Creusot in central France, will start making their way underneath the capital in early 2017.
They will now undergo special factory testing to make sure all components are of the highest quality and fit together perfectly. Once this is finished, they will be dismantled later this year and shipped to London, where teams in Battersea will start their finally assembly – estimated to take around three months.
Each TBM ‘cutting head’, set to do the excavation work, is just over six metres in diameter. The machines themselves are each 106 metres long – equivalent to the length of the pitch at Wembley Stadium.
They will separately take on two individual tunnel drives to build the 5.2m-diameter tunnels. The TBMs will run 24 hours a day, seven days a week, stopping only for scheduled maintenance.
Nick Brown, London Underground’s managing director, said: “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.”
Nearly 20,000 pre-cast concrete segments will be built in rings behind them as they advance. As part of the extension, a 3.2km twin-bore tunnel and two new Tube stations will be built by 2020 – one at the heart of the Battersea Power station redevelopment and another at Nine Elms to the east.
Tunnelling for the extension is due to start early next year and will take six months to complete. This will see over 300,000 tonnes of earth excavated and passed along nine conveyors before being loaded onto barges and taken to Goshems Farm in Essex, where it will be used to create arable farmland by raising former landfill sites.
According to TfL, this way of transporting excavated material will remove over 40,000 lorry journeys from the capital’s road network, reducing traffic congestion and reducing the site’s carbon footprint.
The TBMs, which will both be named by school children, are essential to the Northern Line work, which will extend the line from Kennington to Battersea via Nine Elms. They also form part of wider improvement works taking place along the line, including introducing new signalling to increase capacity by 20% during peak.