Active design in civil tunnelling with sprayed concrete as a permanent lining

摘要

Sprayed concrete in civil tunnelling has been acknowledged world-wide as a legitimate rock support measure. The advantages of the wide range of properties that can be achieved and high application rates allow tunnelling to proceed with minimum delay. In parallel with this, the technology associated with shotcrete is rapidly developing to allow usage as a permanent lining for rock tunnels. In many projects, cast-in-place concrete or similar rigid support measures are the only approved methods for the permanent lining, whilst sprayed concrete is limited to providing temporary support. Modern tunnelling demands cost-effective techniques, long-term durable products, and a safe working environment. These demands require comprehensive documentation to be prepared. In Scandinavia, temporary rock support is generally approved as permanent when conforming to relevant technical specifications. Through project references, this article aims to present and describe the elements which together form a tunnelling method including active design with permanent sprayed concrete lining as an integral part. Two solutions for application of sprayed concrete in adverse rock mass conditions will also be described.