Design and Construction of Crossrail Stepney Green Sprayed Concrete Lined Caverns

Summary

At over 50m long, 17m wide and 14m high the Stepney Green Caverns are the largest caverns ever built using Sprayed Concrete Lining techniques in Central London. This paper describes the design, construction and monitoring of the Primary Sprayed Concrete Lining together with lessons learnt that can be applied to other Crossrail structures. The lining system consists of a fibre reinforced Primary Lining, a waterproofing membrane and a fibre reinforced Secondary Lining. A combination of spray applied and sheet membrane waterproofing was utilised. The permanent Primary Lining was designed to take the full short-term applied ground load and surface surcharges. Additional long-term loads, subsequent to the installation of the Secondary Lining are shared between the two linings. The excavation and support methodology varies along the length of the cavern. The launch chamber was constructed using top-heading, bench & invert, the smaller section of cavern using single side-wall drift and the largest part of the cavern using double side-wall drifts with a central gallery. The cavern profile at each advance was controlled using target-less remote laser scanning equipment, set up at a safe distance from the excavation face. The performance of the lining was constantly monitored using deformation monitoring points, pressure cells, inclinometers, extensometers and piezometers and reviewed daily.