Stepney Green, Crossrail
The new Crossrail line in London divides at Stepney Green, with one line continuing north and one line crossing the Thames to the south. A deep shaft and large mined cavern was required at this location as TBM reception and launch and to accommodate the converging tunnels. The shaft was constructed using deep diaphragm walling techniques. The tunnel cross-passages are some of the largest ever constructed using sprayed concrete lining, being 50m long, 17m wide and 15m high.
ByrneLooby was initially appointed by the specialist contractor Spie to design and detail the diaphragm wall. This wall facilitated the enormous 35m deep excavation, with the wall panels being 1.2m thick and 50m deep. A particular challenge was the detailing of the reinforcement for the wall panels, ensuring these large cages could be safely lifted from horizontal to vertical for placement into the excavation. Each cage weighed 25 tonnes necessitating a robust temporary works design.
Subsequently, the main contractor Dragados-Sisk JV appointed ByrneLooby to design the temporary propping to facilitate excavation of the shaft. We worked collaboratively with Dragados-Sisk to devise the value engineered construction methodology and sequencing and internal support system in order to accelerate the construction program and improve buildability. ByrneLooby also provided guidance on the cross-passage excavation stability and the sprayed concrete lining solution.