Authors: Yabe, Y; Abe, S; Ito, T; Ishida, A; Sugimura, K; Kanematsu, M; Higashi, M; Tadokoro, R; Ogasawara, H; Funato, A; Kato, H; Watson, B; Mngadi, S; Durrheim, R; Hofmann, G; Scheepers, L


DOI https://doi.org/10.36487/ACG_rep/1952_30_Yabe

Cite As:
Yabe, Y, Abe, S, Ito, T, Ishida, A, Sugimura, K, Kanematsu, M, Higashi, M, Tadokoro, R, Ogasawara, H, Funato, A, Kato, H, Watson, B, Mngadi, S, Durrheim, R, Hofmann, G & Scheepers, L 2019, 'In-situ stress around source faults of seismic events in and beneath South African deep gold mines', in W Joughin (ed.), Proceedings of the Ninth International Conference on Deep and High Stress Mining, The Southern African Institute of Mining and Metallurgy, Johannesburg, pp. 399-411, https://doi.org/10.36487/ACG_rep/1952_30_Yabe

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Abstract:
To demonstrate the possibility of stress measurement at depths of more than 3 km, in-situ stress states were determined around the source faults of three seismic events: a Mw2.2 seismic event at about 3.3 km below surface in Mponeng gold mine, a Mw3.5 seismic event at about 3.5 km below surface in the Savuka gold mine, and the Orkney earthquake (Mw5.5), with its hypocentre about 5 km below surface, beneath the Moab Khotsong gold mine. The Mw2.2 seismic event occurred in a 30 m thick gabbroic dyke that intruded into a host rock of quartzite. A 90 m long borehole was drilled to penetrate its source fault. Borehole breakout and core discing were observed in the host rock and the hanging wall of the source fault, i.e., in the dyke. Diametrical core deformation analysis (DCDA) and deformation rate analysis (DRA) were applied to core samples retrieved from the borehole. The DCDA determines the differential stress in the plane normal to a borehole by measuring the cross-section shape of a core sample, while the DRA reproduces the normal stress in the orientation in which a cyclic loading is applied, i.e., to obtain hysteresis of the stress-strain curves. By integrating these measurements and criteria of the borehole breakout and the core discing, the principal stress states in the host rock, the footwall in the dyke and the hanging wall in the dyke were reproduced. Significant differences were found between the stress states in the footwall and the hanging wall. The Mw3.5 seismic event occurred in a 36 m thick dyke called BV78. A tunnel that was damaged by the seismic event passed through the source region. The compact conical-ended borehole overcoring (CCBO) technique was applied at two sites along the tunnel; one site was in an area de-stressed by mining and the other about 10 m from the dyke in an area of increased stress owing to the mining abutment above. DCDA was also applied to the core samples. Three boreholes (Hole A, Hole B and Hole C) that reach an aftershock area in the upper margin of the source fault of the Orkney earthquake (Mw5.5), were drilled by the ICDP-DSeis project (Ogasawara et al, 2019). Since the holes were designed to be drilled in the direction of the maximum compression, borehole breakout or core discing rarely occurred. The DCDA was applied to core samples recovered from Hole A and Hole B. The DRA was also applied to core samples of Hole A. The differential and the normal stresses along Hole A showed a spatial variation that correlates with a variation in lithology and the aftershock distribution.

References:
Barton, C. A., Zoback, M.D. and Burns, K. L. 1988. In-situ stress orientation and magnitude at the Fenton Geothermal site, New Mexico, determined from wellbore breakouts, Geophys. Res. Lett., 15, 467-470.
Funato, A. and Ito, T. 2017. A new method of diametrical core deformation analysis for in-situ stress measurements, Int. J. Rock Mech. Min. Sci., 91, 112-118, .
Hofmann, G., Scheepers, L. and Ogasawara, H. 2013, Loading conditions of geological faults in deep level tabular mines. Proceedings of the 6th Int. Symp. on In-Situ Rock Stress (RS2013), Sendai, Japan.
Jager, A. J. and Ryder, J. A. 1999. A handbook on rock engineering practice for tabular hard rock mines, The Safety in Mines Research Advisory Committee (SIMRAC), Johannesburg.
Kaga, N., Matsuki, K. and Sakaguchi, K. 2003. The in situ stress states associated with core discing estimated by analysis of principal tensile stress, Int. J. Rock Mech. Min. Sci., 40, 653-665.
Matsuki, K., Kaga, N., Yokoyama, T. and Tsuda, N. 2004. Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress, Int. J. Rock Mech. Min. Sci., 41, 1067-1190.
Nakatani, M., Yabe, Y., Philipp, J., Morema, G., Stanchits, S., Dresen, G. and JAGUARS Group.2008. Acoustic emission measurements in a deep gold mine in South Africa—Project overview and some typical waveforms, Seismol. Res. Lett., 79, 311.
Naoi, M., Nakatani, M., Yabe, Y., Kwiatek, G., Igarashi, T., Plenkers, K. 2011. Twenty thousand aftershocks of a very small (M2) earthquake and their relation to the mainshock rupture and geological structures, Bull Seism Soc Am, 101, 2300-2407, .
Okada, Y. 1992. Internal deformation due to shear and tensile faults in a half-space, Bull. Seism. Soc. Am., 82, 1018-1040.
Ogasawara, H., Kato, H., Hofmann, G., and De Bruin, P. 2012. Trial of the BX conical-ended borehole overcoring stress measurement technique, J. SAIMM, 102, 749-754.
Ogasawara, H., Kato, H., Hofmann, G., Roberts, D., Piper, P, Clements, T., Yabe, Y. and Sakaguchi, K. 2013. In-situ stress measurements to constrain stress and strength near seismic faults in deep level South African gold mines. 6th International Symposium on In-Situ Rock Stress (RS2013), Sendai, Japan.
Ogasawara, H., Katsura, T., Hofmann, G., Yabe, Y., Ishii, H., Roberts, D., Nakao, S., Okubo, M., Ward, A. K. and Kawakata, H. 2014. The Ishii strainmeters to in-situ monitor rock mass response to mining in South African gold mines, in Proceedings of the 6th South African Rock Engineering Symposium (SARES), 12–14 May 2014, 21–33.
Sakaguchi, K., Obara, Y., Nakayama, T. and Sugawara, K. 1992. Accuracy of rock stress measurement by means of conical-ended borehole technique, J. Min. Material Process. Inst., Jpn, 108, 455-460.
Sato, N., Yabe, Y., Yamamoto, K. and Ito, H. (2003), In situ stresses near the Nojima fault estimated by deformation rate analysis (in Japanese), Zisin2, 56, 157-169.
Sugawara, K. and. Obara, Y 1999. Draft ISRM suggested method for in situ stress measurement using the compact conical-ended borehole overcoring (CCBO) technique. Int. J. Rock Mech. Min. Sci., 36, 307-322.
Van Aswegen, G. 2017. Seismic sources and rockburst damage in South Africa and Chile. Proceedings of the 9th International Symposium on Rockbursts and Seismicity in Mines (RaSiM9), Santiago, Chile.
Watson, B.P., Sellers, E.J., Kuijpers, J.S., Grave, D.M.H., Roberts, M.K.C. and Coetzer S.J. 2005. Alternative cost effective ways of determining the state of stress in mines. PlatMine report: CSIR, Division of Miningtek, Johannesburg. South Africa.
Wiles, T.2010. Map3D User's Manual, Mine Modelling Pty Ltd - www.map3d.com, Australia.
Yamamoto, K. 2009. A theory of rock core-based methods for in-situ stress measurement, Earth Planets Space, 61, 1143-1161.
Yamamoto, K., Kuwahara, Y., Kato, N. and Hirasawa, T. 1990. Deformation rate analysis: A new method for in situ stress estimation from inelastic deformation of rock samples under uni-axial compressions, Tohoku Geophys. J. (Sci. Rep. Tohoku Univ., Ser. 5), 33, 127–147.
Yabe Y., Song, S. and Wang, C. 2008. In-situ stress at the northern portion of the Chelungpu fault,Taiwan, estimated on boring cores recovered from a 2-km-deep hole of TCDP, Earth Planets Space, 60, 809-819.
Yabe, Y., Yamamoto, K., Sato, N. and Omura, K. 2010, Comparison of stress state around the Atera fault, central Japan, estimated using boring core samples and by improved hydraulic fracture tests, Earth Planets Space, 62, 257-268.
Yabe, Y. and Omura, K. 2011, In-situ stress at a site close proximity to the Gofukuji fault, central Japan, measured using drilling cores, Island Arc, 20, 160-173.
Yabe, Y., Philipp, J., Nakatani, M., Morema, G., Naoi, M., Kawakata, H., Igarashi, T., Dresen, G., Ogasawara, H., JAGUARS-Group 2009, Observation of numerous aftershocks of an Mw1.9 earthquake with an AE network installed in a deep gold mine in South Africa, Earth Planets Space, 61, e49–e52, .
Yabe, Y., Nakatani, M., Naoi, M., Iida, T., Satoh, T., Durrheim, R, Hofmann, G., Roberts, D., Yilmaz, H., Morema, G. and Ogasawara, H. 2013, Estimation of the stress state around the fault source of a Mw2.2 earthquake in a deep gold mine in South Africa based on borehole breakout and core discing, in Proceedings on the 6th International Symposium on In-situ Rock Stress, 20-22 August, 604-613.
Zoback, M. D., Moos, D. and Mastin, L. 1985, Well bore breakouts and in situ stress, J. Geophys. Res., 90, 5523-5530.




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