Crossrail Contract C305
Eastern Running Tunnels
(Limmo Peninsula to Farringdon; Limmo Peninsula to Victoria Dock; Stepney Green to Pudding Mill Lane)
Contract C305 is the biggest design-bid-build construction contract of the CRL project. The contract includes the eastern running tunnels of CRL’s central section with launch shafts and SCL launch adits for TBMs at Limmo Peninsula, SCL caverns and launch adits for TBMs at Stepney Green and 10 SCL cross passages between the running tunnels with lengths up to 30 metres.
According to Crossrail project managers, the Stepney Green caverns are one of the largest mined caverns ever constructed in Europe using a spray concrete lining. The eastbound cavern is where Crossrail trains will branch towards Stratford or Woolwich and so is scaled to accommodate the two tunnel boring machines (TBMs) – Victoria and Elizabeth.
The cavern is 50m long, 13.4m wide and 16.6m high at its widest point. To construct the cavern, the team had to excavate 7500m3 of material and apply 2500m3 shotcrete to the walls.
Due to the site’s urban location, alongside a school and a technical college, a concrete batching plant was built on site to manufacture the concrete for the cavern.
At the Limmo Peninsula site, two 40m deep and 30m diameter shafts were first built. One shaft was sunk using diaphragm walls, the second so called Auxiliary shaft was built utilising the SCL construction method. At the bottom of each shaft two 15m long and 8m wide SCL launch adits were excavated and two 55m long and 8m wide SCL tunnels constructed in order to connect both shafts. All SCL works at Limmo Peninsula followed a Top Heading, Bench and Invert excavation sequence and were carried out in London Clay.
This project has seen Hanson UK supply to date:
- Stepney Green – 11km3 spray concrete lining supplied 24/7 over 9 months
- Limmo Peninsula – 7.5km3 spray concrete lining supplied 24/7 over 8 months
- Primary lining mix contains retarder, super-plasticiser, microsilica and steel fibres
- Secondary lining contains poly fibres (for fire retardation) instead of steel fibres.