Identification of Grouting Discontinuity of Rock Bolts as an Efficient Way to Control Safety Conditions in Mine Roadways

摘要

A rock bolt which is grouted underground may not be properly installed with the result being a discontinuity of the resin layer. Such discontinuity may also occur in working conditions due to typical rock behaviour and displacement. It may be very hazardous to mine safety. In this paper an outline of a method for non-destructive identification of a discontinuity of a resin layer surrounding rock bolt is presented. The method uses modal analysis procedures and is based on an impact excitation where a response transducer is positioned at a visible part of a rock bolt. As an installed rock bolt acts as an oscillator, different lengths of discontinuity of resin layer change its modal parameters. By proper extraction of these parameters, from which a resonant frequency is seen as most valuable, the intended identification is possible. The results of identification of resin discontinuities are discussed. Experiments were performed in an experimental coal mine as well as in coal and copper mines. Also the influence of explosions on installed rock bolts is presented.