Design of Sprayed Concrete Linings in Soft Ground — A Crossrail Perspective

Many people in the past have questioned the method so this paper starts with a definition of the term: An SCL tunnel is a tunnel with a Sprayed Concrete Lining. The Sprayed Concrete Lining interacts with the ground and, through the choice of excavation sequence, this interaction can be optimized to minimize the loads on the ground support. Monitoring is required for “performance verification”, to ensure that the tunnel is performing within the limits required by the design (given natural variations, for example, in advance rates and ground conditions), to determine when certain contingency measures are needed (such as temporary inverts).