Comparison Between Sprayed and Cast In-Situ Concrete Secondary Linings at Bond Street and Farringdon Stations

It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology—such as the use of wet mix processes, improved accelerators, fibre reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes—have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining. ^[1]