Fourteen kilometres of station and platform tunnels, passenger walkways and other spaces have been created through a mining technique known as sprayed concrete lining.
The sprayed concrete lining method has been used extensively on Crossrail to form each of the station platform tunnels, cross-passages between the platform tunnels, ventilation tunnels, concourse tunnels, cross-over caverns and ventilation, escape and intervention shafts across the central section of the route.
The technique involves spraying a quick setting form of concrete strengthened with steel fibres onto freshly excavated ground to seal the new tunnels. Further layers are added to make the surface watertight creating a permanent structure some 65cm thick.
This process enables huge underground spaces and curved walls to be created.
Sprayed concrete lining was used to create the station tunnels at five of the Elizabeth line's central London stations – Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel.