Mining Latin America / Minería Latinoamericana

pp 241-255

Application of a statistical analysis technique for design of high rock slopes at Palabora mine, South Africa

  • D. C. MartinAffiliated withPiteau Associates Engineering, Ltd.
  • , N. S. L. SteenkampAffiliated withPalabora Mining Company
  • , J. W. LillAffiliated withPalabora Mining Company

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This paper describes the engineering geology, structural geology, stability analysis, and design of slopes for the open pit copper mine of Palabora Mining Company located in South Africa. The pit occurs in generally hard, jointed rock. Because of the large size, low grade and geometry of the orebody, it is imperative to minimize the waste to ore ratios and hence mine to stringent plans incorporating maximum safe working slope angles.

Stability of interramp slopes in most areas is controlled by numerous possible wedge and plane failures on benches. Stability analyses were conducted by dividing the pit into design sectors. A unique statistical analysis technique which combines the results of limit equilibrium analysis of each potential failure mode with orientation and intensity of discontinuity populations was used to design benches and interramp slopes in each design sector. The statistical significance of each failure mode was assessed using cumulative frequency plots. Slope design charts were developed based on slope geometry and failure geometry. The effects of observed bench break back and documented behaviour of slopes were also incorporated into the analysis to enable preparation of an effective slope design.

Implementation of the slope design technique for 200 to 350m high slopes which have been excavated at Palabora is reviewed and the slope performance is assessed from both an operations and stability perspective.