Evaluation of acoustic attenuation as an indicator of roof stability in advancing headings

A novel acoustic technique developed to monitor roof stability in advancing headings was evaluated during a field monitoring trial at the Brunswick Mi ne, New Brunswick, Canada. The acoustic technique uses waveforms generated by mining activity near the active race (such as rotary-percussion drilling for the installation of support or drilling blast-holes) to identify chang es in the attenuation properties of the roof rock mass which are correlated to stability through conceptual models and independent experimental work. Field trial results indicate that (a) the selected frequency range of the a coustic sensors is suitable to ensure that recorded waveforms have originat ed within the rock mass volume of interest near the face of the active head ing, (b) the waveforms generated by rotary-percussion drilling are sufficie ntly consistent to be considered as a stable acoustic source, and (c) obser ved changes in roof attenuation are consistent with what would be expected in response to the installation of support near the freshly blasted face an d blast-hole drilling of the face. (C) 2000 Elsevier Science Ltd. All right s reserved.