Sister machine Sophia is being prepared to start the drive from Woolwich under the Thames.
The thousand tonne machine Mary started her journey from Plumstead in May. During her three month journey, Mary has excavated almost 110,000t of material and installed 811 concrete rings to line the inside of the tunnel.
Sophia had reached the Woolwich box in May and is being prepared to start on the second leg of the journey underneath the Thames to North Woolwich.
Gus Scott, project manager for Crossrail’s Thames Tunnel, said: “It’s great to know that we’re half way through our tunnelling in southeast London. Mary and Sophia have done a fantastic job so far, between them constructing a mile and a half of brand new tunnels from Plumstead to Woolwich.”
The Thames tunnel, which will run from Plumstead, via Woolwich and underneath the Thames to North Woolwich. They are different to the tunnelling machines being used elsewhere on Crossrail. The two slurry machines have been are equipped to deal with the chalk, flint and wet ground conditions in southeast London.
As part of the tunnelling process, the excavated soils are pumped out as liquid slurry to a site treatment plant at Plumstead. The slurry is separated into sand, gravel, water and chalk. The chalk comes out in ‘cakes’ or slabs of filtered chalk particles.