TY - JOUR
T1 - Integration of underground mapping, petrology, and high-resolution microseismicity analysis to characterise weak geotechnical zones in deep South African gold mines
AU - Mngadi, S. B.
AU - Durrheim, R. J.
AU - Manzi, M. S.D.
AU - Ogasawara, H.
AU - Yabe, Y.
AU - Yilmaz, H.
AU - Wechsler, N.
AU - Van Aswegen, G.
AU - Roberts, D.
AU - Ward, A. K.
AU - Naoi, M.
AU - Moriya, H.
AU - Nakatani, M.
AU - Ishida, A.
AU - SATREPS Team, Team
AU - ICDP DSeis Team, DSeis Team
N1 - Funding Information:
Sibanye gold limited is acknowledged for providing permission to publish the results. The authors thank the School of Geosciences and the School of Mining Engineering at the University of the Witwatersrand, Center of Excellence for Integrated Mineral and Energy Resources Analysis (CIMERA), the The Council for Scientific and Industrial Research (CSIR), JST-JICA, SATREPS team, ICDP DSeis team for the use of their resources and facilities. This project was also funded by JSPS KAKENHI grants 21224012, 21246134, 26249137, the MEXT's Earthquake and Volcano Hazards Observation and Research Program, and the Earthquake Research Institute, the University of Tokyo cooperative research program. RJD acknowledges the support of the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation.
Funding Information:
Sibanye gold limited is acknowledged for providing permission to publish the results. The authors thank the School of Geosciences and the School of Mining Engineering at the University of the Witwatersrand , Center of Excellence for Integrated Mineral and Energy Resources Analysis ( CIMERA ), the The Council for Scientific and Industrial Research ( CSIR ), JST-JICA , SATREPS team, ICDP DSeis team for the use of their resources and facilities. This project was also funded by JSPS KAKENHI grants 21224012 , 21246134 , 26249137 , the MEXT’s Earthquake and Volcano Hazards Observation and Research Program, and the Earthquake Research Institute, the University of Tokyo cooperative research program. RJD acknowledges the support of the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation .
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/2
Y1 - 2019/2
N2 - A highly-stressed shaft pillar is prone to large seismic events, falls of ground and rockbursts, which may cause injuries and loss of production, especially in weak geotechnical zones. It is thus important to identify weak geotechnical zones in order to mitigate risks. In this study, we present integrated studies (underground mapping, petrology, rock mechanics and high-resolution microseismicity analysis) to understand the different geotechnical zones in the shaft pillar of Cooke 4 mine in South Africa. The footwall of the remnant shaft pillar comprises the Upper Elsburg reef of the Mondeor Formation, while the Ventersdorp Contact Reef (VCR) of the Venterspost Formation and soft/weak lavas of the Westonaria Formation form the hangingwall. Results from underground mapping and microscopic analysis show that the shaft pillar is composed of quartzites, pebbly quartzites, argillaceous quartzites and conglomerates. Underground mapping further shows that the shaft pillar is characterized by several discontinuities, which vary from minor to macro scale fractures. Laboratory uniaxial compressive strength (UCS) tests indicate that quartzite has the strongest strength, followed by pebbly quartzite, argillaceous quartzite and lastly, conglomerate. Analysis of high-resolution acoustic emissions (AEs) clusters indicates that the majority of AEs are associated with the mining stope faces. The clusters show the formation of Ortlepp shears ahead of the stope, which is caused by the excavation-induced stress field. Microseismic data further reveal that the fracture turning-point occurs in the soft strata (weak hangingwall lavas). The integration of these datasets has allowed us to develop the fracture model for different geotechnical zones, which concurs with previous models developed for the similar underground environment (i.e., weak/soft lava hangingwall and quartzite/conglomerate footwall). This has major implications for future mining, support, production and safety.
AB - A highly-stressed shaft pillar is prone to large seismic events, falls of ground and rockbursts, which may cause injuries and loss of production, especially in weak geotechnical zones. It is thus important to identify weak geotechnical zones in order to mitigate risks. In this study, we present integrated studies (underground mapping, petrology, rock mechanics and high-resolution microseismicity analysis) to understand the different geotechnical zones in the shaft pillar of Cooke 4 mine in South Africa. The footwall of the remnant shaft pillar comprises the Upper Elsburg reef of the Mondeor Formation, while the Ventersdorp Contact Reef (VCR) of the Venterspost Formation and soft/weak lavas of the Westonaria Formation form the hangingwall. Results from underground mapping and microscopic analysis show that the shaft pillar is composed of quartzites, pebbly quartzites, argillaceous quartzites and conglomerates. Underground mapping further shows that the shaft pillar is characterized by several discontinuities, which vary from minor to macro scale fractures. Laboratory uniaxial compressive strength (UCS) tests indicate that quartzite has the strongest strength, followed by pebbly quartzite, argillaceous quartzite and lastly, conglomerate. Analysis of high-resolution acoustic emissions (AEs) clusters indicates that the majority of AEs are associated with the mining stope faces. The clusters show the formation of Ortlepp shears ahead of the stope, which is caused by the excavation-induced stress field. Microseismic data further reveal that the fracture turning-point occurs in the soft strata (weak hangingwall lavas). The integration of these datasets has allowed us to develop the fracture model for different geotechnical zones, which concurs with previous models developed for the similar underground environment (i.e., weak/soft lava hangingwall and quartzite/conglomerate footwall). This has major implications for future mining, support, production and safety.
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U2 - 10.1016/j.ijrmms.2018.10.003
DO - 10.1016/j.ijrmms.2018.10.003
M3 - Article
AN - SCOPUS:85059346741
SN - 1365-1609
VL - 114
SP - 79
EP - 91
JO - International Journal of Rock Mechanics and Minings Sciences
JF - International Journal of Rock Mechanics and Minings Sciences
ER -