The Northern Line Extension project took a step forward when Helen, the first of two giant tunnel boring machines, set off under south London to create the first of the underground tunnels that will extend the Charing Cross branch of the Northern line from Kennington to Battersea Power Station, via Nine Elms. The other tunnel boring machine, Amy, will start operations in around a month.
Each machine is capable of tunnelling up to 30 metres a day with teams of around 50 people operating them. Tunnelling is expected to take around six months to complete. As the 100 metre long tunnelling machines advance forward, nearly 20,000 precast concrete segments will be put in place to form rings to line the tunnels. A conveyor system will then take the spoil from the tunnels up to barges on the River Thames.
The extension, targeted for completion in 2020, is the first major Tube line extension since the Jubilee line in the late 1990s.
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