Crossrail’s fifth TBM, Sophia, has started drilling a tunnel under the River Thames from the project’s Plumstead portal.
Sophia will drill at an average rate of around 100 metres a week, installing precast concrete segments as rings to form the tunnel lining as she goes.
Unlike the tunnel boring machines currently in operation, Sophia is specially equipped to handle the chalk, flint and wet ground conditions she will encounter in southeast London.
As part of the tunnelling process, the excavated soils will be pumped out as liquid slurry to a special treatment plant at Plumstead. The slurry will be separated into sand, gravel, water and chalk. The chalk will come out in ‘cakes’ or slabs of filtered chalk particles.
Stephen Hammond, Crossrail Minister, said: “The launch of Sophia, Crossrail’s fifth tunnelling machine, demonstrates the great progress the project is making, stimulating the economy, generating thousands of jobs during construction and delivering huge transport improvements to people living in southeast London.”
Across the whole Crossrail project, eight tunnelling machines will construct 21 kms (13 miles) of twin tunnels under London. The Crossrail route will pass through 37 stations and run 118 km (73 miles) from Maidenhead and Heathrow in the west, to Shenfield and Abbey Wood in the east.
