BX CCBO in-situ stress measurements at earthquake prone areas in South African gold mines -a summary of mini-workshop on 13 Feb 2014

H. Ogasawara, H. Kato, G. Hofhann, D. Roberts, P. Piper, T. Clements, A. K. Ward, Yasuo Yabe, H. Yilmaz, R. J. Durrheim

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

Downsizing an overcoring diameter to 60 mm (BX), the Compact Conical-ended Borehole Overcoring technique (BX CCBO) proved suitable for adverse conditions and difficult access from surface in deep levels South African gold mines. BX CCBO in-situ stress measurements have been carried out at seven sites at depths of 1.0 to 3.4 km, the measured maximum principal stresses, a ranging between 76 and 146 MPa. In South African gold mines, such a number of in-situ stress measurements have never been camed out previously in the σ1 and depth ranges relevant to the described studies. The in-situ stress measurements allowed us to confirm that an assumption on far-field (initial) stress gradient was acceptable with only slight modifications. An improved assumption on far-field stress gradient allowed us to better constrain both the stress and strength on the M>2 earthquake faults with σ1 ranging between 100 and 177 MPa. The stress range was also confirmed by analyzing breakouts and core discings ins hole drilled through a M12.1 hypocenter. At one site where σ1 was 100 11 OMPa, a BX CCBO was compared with a CSIRO cell in a good agreement, although some issues were found to address regarding BX CCBO measurements.

Original languageEnglish
Title of host publication48th US Rock Mechanics / Geomechanics Symposium 2014
EditorsLee Petersen, Ray Sterling, Emmanuel Detournay, Will Pettitt, Joseph F. Labuz
PublisherAmerican Rock Mechanics Association (ARMA)
Pages924-934
Number of pages11
ISBN (Electronic)9781634395236
Publication statusPublished - 2014 Jan 1
Event48th US Rock Mechanics / Geomechanics Symposium 2014: Rock Mechanics Across Length and Time Scales - Minneapolis, United States
Duration: 2014 Jun 12014 Jun 4

Publication series

Name48th US Rock Mechanics / Geomechanics Symposium 2014
Volume2

Other

Other48th US Rock Mechanics / Geomechanics Symposium 2014: Rock Mechanics Across Length and Time Scales
CountryUnited States
CityMinneapolis
Period14/6/114/6/4

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology

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