13 April 2017

Tunnelling Begins on the Northern Line Extension

A giant tunnelling machine named Helen has set off on a subterranean journey from Battersea Power Station. The new tunnel will connect the Power Station and Nine Elms to the London Underground system.

Helen was lowered down into the excavations for our new Underground station to the south of the Power Station building in February. The mighty machine has now begun a 3.2km journey to Kennington, where the new section of line will join the existing network. A sister machine, Amy, will set off from the Power Station in approximately one month to bore the other tunnel.

As the 100m-long machines grind their way through the earth below the city, the excavated spoil is conveyed back down the tunnel and up to the surface. It then moves on an elevated conveyor system across the Power Station site to barges on the Thames, and the barges take it to Goshems Farm in East Tilbury, Essex where it will be used to create new arable farmland.

Each machine is capable of tunnelling up to 30 metres a day and requires a crew of 50 people to operate it. As the machines move forward, 20,000 pre-cast concrete segments will be inserted behind them, forming rings to line the tunnels. The new Underground line is expected to be complete in 2020.

It’s a tradition in the tunnelling industry that boring machines cannot start work until they have been named. Following a vote by local schoolchildren, the Northern Line Extension machines were named after Britain’s first astronaut, Helen Sharman, and aviation pioneer Amy Johnson.