Development of in-situ rockburst precursor warning systems

Abstract

Research was initiated to investigate methods whereby the phenomenon of in-situ rockbursting could be effectively monitored and predicted using innovative acoustic sensing/recognition technology. This technology has been developed by the Queen's University Department of Mining Engineering to complement existing rockburst monitoring systems currently being used by mines to identify rockburst event source locations in post-event cases. Both equipment and software technology necessary to permit successful monitoring of high-frequency acoustic emissions and the limited capability to assess variation in ground stress states leading to possible rockburst instability in pillar-associated ground were successfully developed. Standard microcomputing hardware and software was developed for the purpose of enabling in-situ installation studies. During field trials, individual microseismic monitoring units were observed to perform with oustanding success for periods in excess of two years with minimum maintenance. A series of six different pillar sites, each subjected to dissimilar stress influence, were identified for monitoring purposes; of the six, three were selected for long term microseismic evaluation. On the basis of in-situ stress analysis, stress modelling review and acoustic emission data obtained, significant differences in site behaviour were observed. Specific software, derived from pattern recognition technology, has permitted the rapid and efficient evaluation of site stress conditions and has been shown to be successful in identifying differences in site stress conditions solely on the basis of acoustic emission examination. In one instance, successful mapping of gradual stress build-up within a rib pillar, tributary to pillar extraction operations, resulted in the capture of a localized rockburst event and the subsequent characterization of acoustic data associated with the rockburst event.