This guide for practising tunnelling engineers sets out the state of the art of composite sprayed concrete lined (SCL) tunnels. It covers the full process of design, materials specification, analysis, instrumentation and monitoring, and construction of composite SCL tunnels with a sprayed waterproofing membrane in soft ground. It is illustrated with worked examples, and considers the wide range of factors and influences from the construction method, the choice of waterproofing membrane and representation of the construction sequence in the analysis and design. Particular focus is on the primary-secondary lining interaction with different types of waterproofing systems, such as sprayed waterproofing and direct concrete-to-concrete contact. Jiang Su is a Chief Tunnel Engineer and Tunnel and Underground Space Discipline Lead at AtkinsRéalis, UK. Since completing his PhD on composite sprayed concrete lined tunnels, he has been involved in most major tunnelling projects in the UK that involve a composite lining configuration.
