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This paper presents the methodology and results of a borehole breakout study using acoustic televiewer borehole images (ATV) as part of the geotechnical investigations at Olympic Dam mine in South Australia.
ATV logging of boreholes is rapidly becoming a standard investigation tool for geological and geotechnical investigations. It is primarily being used to provide high quality structural orientation data. However, the ability to observe and measure borehole breakout provides information on in situ stress and is another benefit of this technique.
This study located 154 cases of breakout in 38 of the 96 holes reviewed. The measurements are presented and compared with conventional stress testing from the existing underground operation comprising CSIRO HI-Cell and Acoustic Emission.
This study presents a summary of the stress condition at Olympic Dam. Clear stress domains are apparent with perturbation adjacent to a known major structure that transects the deposit. The study demonstrates the reliability of borehole breakout as a means of estimating the stress field orientation and its usefulness in augmenting smaller data sets of conventional methods.
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