Summary

Characterization of fractures is an important factor in the assessment of the quality and strength of rock masses. Conventional seismic techniques of quantifying the broken-ness of rocks have concentrated on the use of velocity, but this has not resulted in unique interpretations. As part of a research project to assess fracturing in rock masses on opencast coal sites, empirical correlations are being developed which relate fracture characteristics to the attenuation of seismic signals.

An experimental programme into the design of efficient blasting/fragmentation systems in opencast mining is outlined. The programme involves the seismic assessment of rock brokenness before and after blasting, together with the associated ground vibrations and excavation process, in order to optimize blast fragmentation efficiency. The results show that the fragmentation efficiency of a mine blast can be quantified in terms of 3-D seismic attenuation spectra and polar anisotropy diagrams. These 3-D spectra and polar plots from a sequence of seismic experiments are then correlated with 3-D excavation efficiency profiles, blast and ground vibration spectral data in the optimization study. A data case study is given to highlight the scope of the data collected and the type of multivariate statistical analysis methods used.

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