Seismic response to mining the massive ore body at South Deep gold mine

Authors: Naicker, N Download Paper

DOI https://doi.org/10.36487/ACG_rep/1952_26_Naicker

Cite As:
Naicker, N 2019, 'Seismic response to mining the massive ore body at South Deep gold mine', in W Joughin (ed.), Deep Mining 2019: Proceedings of the Ninth International Conference on Deep and High Stress Mining, The Southern African Institute of Mining and Metallurgy, Johannesburg, pp. 347-362, https://doi.org/10.36487/ACG_rep/1952_26_Naicker



Abstract:
Mining currently takes place at depths of between 2400 m and 2650 m below surface at South Deep gold mine. The ore body comprises Witwatersrand conglomerates and varies from 1 m to 120 m thick and extends over several kilometres. A mining method, specific to the geometry of the ore body, is utilized and comprises an initial destressing cut followed by massive mining in the destressed shadow. A high profile stoping (HPS) mining method was introduced to reduce or eliminate many of the mining difficulties experienced with the previous low profile stoping (LPS) method. A system of regional stabilising pillars, together with the placement of backfill is utilized to minimise seismic energy emissions. Improvements to the ground support to mitigate rockburst damage were introduced and further improvements are ongoing. A mine-wide seismic system comprising 35 sensors is used to monitor seismic activity. Attempts to improve seismic monitoring include velocity calibrations, sensor orientation studies, more accurate determination of the attenuation factor (Q) and batch reprocessing of data to ensure consistency across software versions. In this paper, the level of seismic activity in relation to the level of production, inclusive of production ramp ups and stoppages, from different sections of the mine, is evaluated. The type and severity of damage to workings is assessed together with a comparison of peak particle velocities at the damage locations. Preconditioning, other rockburst risk mitigation strategies and the sources of seismicity (in particular the role of geological features), are assessed. The seismic hazard for different periods of time is calculated.

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