Publications / 1994 Proceedings of the 11th ISARC, Brighton, United Kingdom
The lining of shafts and tunnels with spray concrete is well established. The health hazards associated with spraying in confined areas, as well as the dangers of rockfalls make the remote operation of this process highly desirable. This paper describes an established system for remotely spraying concrete in shafts, which has been recently modified for use in tunnels. The Shelob spraying machine relies on a rapidly rotating disc that flings the concrete onto the shaft or tunnel walls. The process was developed by Caledonian Mining Company and has been highly successful in spraying linings to shafts in the UK and Africa. The fundamental requirements of a sprayed concrete lining are considered and then the alternative methods of dry spraying, wet spraying and disc spraying are compared. As well as health and safety considerations,, the rate of material application and the efficiency of application are important. The amount of rebound and the quantity required to guarantee the design thickness can be as important as the rate of material emerging from the nozzle. The spinning disc philosophy has many advantages over the traditional nozzle spraying and its robust and simple operation makes remote spraying very practical.