Excerpts taken from abstracts in CIM Journal, Vol. 7, No. 2.
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J. H. Reeves, Newspar, St. Lawrence, Newfoundland; B. A. Sparkes, Canada Fluorspar (NL) Inc., St. Lawrence, Newfoundland; N. Wilson, Newspar, St. Lawrence, Newfoundland
ABSTRACT The St. Lawrence Granite hosts vein-type fluorite mineralization that was mined until 1977. Recent drilling identified a significant fluorite-bearing structure hosted in adjacent meta-sedimentary country rocks. Several phases of vein fill and brecciation indicate there are three phases of fluorite mineralization, of which the later two phases are volumetrically significant. The earliest fluorite is purple and occurs along joint and fracture surfaces, in fault-breccia matrices, and as stockwork veins. The second phase comprises primarily red, yellow, blue-green, and white colours of fluorite. The latest phase is green with lesser clear fluorite. Identification of fluorite veins in the meta-sedimentary rocks opens up new areas for exploration.
J. M. Reyes-Montes, SeisQ Consulting, Shrewsbury, Shropshire, United Kingdom; B. L. Sainsbury, Monash University, Clayton, Victoria, Australia; J. R. Andrews, Caltech Seismo Laboratory, Pasadena, California, USA; R. P. Young, University of Toronto, Toronto, Ontario, Canada
ABSTRACT Microseismic monitoring provides insight into the location and extent of rock-mass fracturing induced by cave mining, enabling interpretation of the cave profile and validation of predictive numerical models. Source location uncertainties can lead to misinterpretation of the inferred characteristics of the fracture network. One principal source of uncertainty is the velocity model used to invert the location algorithm. Large-scale 3D numerical models of modulus changes across a caved mass can represent such complexities in the location algorithms, allowing more accurate interpretation of the microseismic activity. A Northparkes mine case study applies this advanced approach to microseismic data interpretation.
M. R. P. Snow, Queen’s University, Kingston, Ontario, Canada
ABSTRACT TThis paper outlines geotechnical conditions that commonly exist in underground, hardrock mines and the challenges posed for ground-support steel, specifically rockbolts, used in these environments. A model is proposed whereby the in-situ stress and rock-mass classifications (based on Bieniawski’s rock mass rating) form the basis of determining the desired steel properties of the rockbolts used. Based on the ASTM F432 bolting specification, recommended minimum steel properties are defined for three ranges of in-situ stress levels, each with their own six ranges of RMR values. Heat treatment for the steel can be specified once these minimum steel properties are known.