London Underground has shown off the two new tunnel boring machines that will soon start chewing through South London to dig the Northern line extension.
The two machines – which were built in France – will be tested, and later this year shipped to London. Engineers in Battersea will then start their final assembly, which is estimated to take three months.
Each TBM ‘cutting head’ which will do the excavation work is just over six metres in diameter. At over 100 metres 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 5.2 metre diameter tunnels.
As they advance forward, nearly 20,000 pre-cast concrete segments will be built in rings behind them.
Tunnelling for the Northern Line Extension, which will extend the line from Kennington to Battersea via Nine Elms, is due to begin in early 2017 and will take six months to complete. Two new stations will be built: one at Battersea Power Station and another at Nine Elms.
The tunnelling will see over 300,000 tonnes of earth excavated and pass along nine conveyors before being loaded onto barges and taken to Goshems Farm in East Tilbury, Essex where it will be used to raise former landfill sites to create arable farmland.