CONTROLLING ROCKBOLT TENSIONING

When current rockbolt tensioning procedures are employed to provide a predetermined restraint for tunnel rock support, problems ensuring that the correct tension is locked into each bolt are routinely encountered. To eliminate these problems, a minor conversion of the bolt involving the incorporation of a tension control sensor has been investigated. The design principle and conversion technique are outlined and the results of a full scale trial at Pen-y-Clip Tunnel in North Wales are described to demonstrate the practical application of the system for improved control of lock off loads.