Research has been undertaken through sponsorship of the Workplace Safety and Insurance Board of Ontario (WSIB) to characterize the support capabilities of conventional and innovative spray-on lining materials for mitigating dynamic failure effects created by simulated rockbursts. A variety of conventional spray support media (shotcrete and fibrecre te linings) and innovative polymer-type spray-on lining materials (TSL's) were subjected to the effects of blasting shock by near surface crater blasting to simulate rockburst influence. In similar fashion, rockbolt and bolt-and-mesh support networks were additionally tested to provide baseline comparison of support media capability to resist simulated rockburst damage. The capacity of various types of surface support agents to mitigate rock damage induced by rockbursting was assessed based upon completion of large-scale field detonation trials. Blast effects and site conditions were observed seismically and photographically to provide detailed information concerning rock heave, surface fracturing, ejected fragment motion and support media survivability characteristics. The relative effectiveness of a wide range of area support methods for suppressing dynamic rock ejection and both rock and support media damage was assessed. Results of the study have validated that the majority of thin, spray-on lining products currently available for mining use may be equally as effective, and often better, than conventional support materials for mitigating rockburst damage in highly stressed mine environments.
1. INTRODUCTION
The need to supply effective area ground support is urgent when it is realized that one third of all fatal accidents, and a large proportion of serious injury incidents, which occur in hard rock mines in Ontario result from falls of ground and rockbursts [1]. Because future mining development will take place at greater depth, the incidence of stress-induced rock falls is also projected to increase. One way in which injury reduction may occur might be through use of rapidly deployable thin spray-on linings, commonly designated TSL's.
Several research efforts that focus upon TSL support use have been undertaken under the sponsorship of the Workplace Safety and Insurance Board of Ontario (WSIB). Appropriate quality control and physical testing procedures for characterizing spray-on support materials, able to meet the highest possible regulatory and industry standards possible, were recommended through the initial phase of this research program. In a subsequent phase, large scale blasting trials were undertaken to test the effectiveness of some types of TSL's for mitigating dynamic rock ejection hazards that would occur in simulated rockburst events.
2. STANDARDIZED ACCEPTANCE CRITERIA
A range of polymer or like products exist or are being developed that may generate significant area support for rock. The extent of support claims that have been made for such materials is, however, poorly substantiated due to the relative infancy of use of such products in commercial support application. Industry efforts for material testing, due to lack of resources or inability to test materials in uniform fashion, are unable to yield comprehensive, quantifiable and comparable material evaluations for all candidate materials available.
