Crossrail construction at Stepney Green shaft marked a major milestone this week with the completion of the eastbound cavern ahead of schedule, with work on the westbound cavern well underway.
The Stepney Green caverns are one of the largest mined caverns ever constructed in Europe using a tunnelling technique called 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) that are due to arrive later this year.
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, neighbouring a school and a technical college; a concrete batching plant was constructed on site to manufacture the concrete that is being used to construct the cavern. The team also used a special cutting tool to remove temporary supports, rather than the traditional noisier method of using an impact hammer.
Sprayed Concrete Lining (SCL) Construction Manager, Rob Gordon, said: “Getting to this stage in our programme in just over three months is an incredible achievement, especially given the site constraints.”
Throughout the works, the team has ensured close monitoring and control of concrete strength and ground movements.
Project Manager Peter Main commented: “Thanks to thorough planning and collaboration by our Sprayed Concrete Linings team, our contracor Dragados Sisk JV and Crossrail, we remain well on schedule for the arrival of the TBMs later this year.”
Stepney Green will have a critical role to play when Crossrail opens; it is where the railway divides with the southeast spur running underground to Plumstead and then onto Abbey Wood via Canary Wharf and the north east spur running underground to Pudding Mill and then onto Shenfield in Essex.
Two of Crossrail’s large tunnel boring machines, Victoria and Elizabeth, will pass through the cavern later this year on their way to Farringdon via Canary Wharf, Whitechapel and Liverpool Street stations.