In-tunnel depressurisation for SCL tunnels at Whitechapel and Liverpool Street stations

Crossrail contract C510 comprises the excavation of platform tunnels, concourse tunnels, cross-passages, escalators and ventilation ducts for the new Whitechapel and Liverpool Street Stations in London. The tunnels have been excavated using Sprayed Concrete Lining (SCL) techniques.

Works for both stations started with the sinking of an Access Shaft which allowed for the opening of two central cross-passages and the platform tunnels 30 m below surface, see Figures 1 and 2. The platform tunnels are approximately 240 m long, and these were mined in two stages: an initial pilot tunnel of approximately 6.3 m outside diameter was excavated first, followed by the 10.5 to 11.5 m diameter enlargement.