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A case study examination of two blast rounds at a Nevada gold mine.

McHugh-E; Warneke-J; Caceres-C
J Explos Eng 2008 Nov/Dec; 2:34-40, 44
Falls of ground are a significant hazard for underground miners and a leading cause of fatalities. A majority of metal and non-metal mines use drill and blast techniques for drifting and primary development. After blasting, the broken rock is mucked out. This is followed by scaling or "barring down" to remove any loose rock from roof, walls and face. The stability of the workplace is then secured using rock bolts, mesh, shotcrete or other appropriate support systems. The entire process is then repeated. All of these activities are potentially hazardous to the miners that perform them. This hazard level is increased if care is not exercised in protecting the opening perimeter through the use of careful blasting practices. In particular, unwanted blast damage to the perimeter rock increases the hazard to those involved in the scaling and reinforcement tasks. It has been found that a majority of ground fall injuries involve blocks formed within the half-meter of rock immediately surrounding an excavation (Bauer et al., 1999; Mark and Iannachione, 2001). Whyatt et al (2003) summarized methods of assessing blast induced damage in underground mines and discussed the feasibility of improving ground control results through the use of controlled blasting. Iverson et al (2007) outlined an approach for assessing perimeter blast damage based on rock mass quality, seismic response, and laser scanning. To assist industry in adapting good perimeter control blasting practices, the Spokane Research Laboratory (SRL), of the National Institute for Occupational Safety and Health (NIOSH), has implemented a program focused on developing practical, yet technically sound, perimeter blasting design procedures. The objective is to provide techniques so that the as-built openings closely resemble those designed. When applied, these will assist mine operators to create stable underground openings with a minimum amount of loose or damaged surrounding rock, thereby enhancing the safety of miners. The overall research and development program involves theoretical, laboratory, field and modeling studies. The results are being integrated into a user-friendly blast design software package. Field studies are an important component of the program. The purpose of the field studies conducted by NIOSH is to fully document the results of a number of blast rounds carried out under a wide range of rock conditions The documentation includes: the blasting patterns, the actual versus the as-designed drillhole locations and orientations, the final excavation profile, the seismic records from the blast, the rock mass quality, the ground support, and a number of other parameters. The results of this study will provide valuable baseline information on fragmentation practices and add to data compiled on mining conditions in different geologic settings. This paper presents some preliminary results of studies carried out at the SSX-Steer Mine.
Mining-industry; Injuries; Injury-prevention; Underground-mining; Accidents; Accident-prevention; Geology; Rock-mechanics; Rock-falls
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Journal Article; Trade
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The Journal of Explosives Engineering