Application of a statistical analysis technique for design of high rock slopes at Palabora mine, South Africa
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.
KeywordsSlope Stability Analysis Design Sector Wedge Failure Limit Equilibrium Analysis Peak Orientation
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- 1.Crosson, C.C., 1983. “Evolutionary Development of Palabora”. Copper 83 IMM Conference, London November, pp. A58 - A69.Google Scholar
- 2.Farquier, G.P. 1983. “Trim Blasting and Double Benching for Steeper Slopes and Competent Walls at PMC”. Engineering and Mining Journal. 184 pp. 46–52 April.Google Scholar
- 3.Herget, G., 1977. “Structural Geology”, Chapter 4, Pit Slope Manual, CANMET Pit Slope Project, 1972/1977, Ottawa.Google Scholar
- 4.Martin, D.C. and Piteau, D.R., 1978. “Select Berm Width to Control Local Failure”. Engineering and Mining Journal. McGraw Hill, June, pp. 161–164.Google Scholar
- 5.Piteau, D.R., 1971. “Geological Factors Significant to the Stability of Slopes Cut in Rock” in Planning Open Pit Mines, S. Africa Inst. of Mining and Metallurgy Symposium, Johannesburg. P.W.J. Van Rensburg ed., Balkema, Amsterdam, pp. 33–53.Google Scholar
- 6.Piteau, D.R. and Martin, D.C., 1977. “Slope Stability Analysis and Design Based on Probability Techniques at Cassiar Mine.” CIM Bulletin Vol$170, No. 779, March. pp. 139–150.Google Scholar
- 7.Piteau, D.R., Martin, D.C. and Trenholme, B.S., 1980. “Slope Stability Analysis and Design of Slopes in the Copper Open Pit”. Unpublished report to Palabora Mining Company May 145 p.Google Scholar
- 8.Piteau, D.R., Stewart, A.F., Martin, D.C. and Trenholme, B.S., 1985. “A Combined Limit Equilibrium and Statistical Analysis of Wedges for Design of High Rock Slopes”. ASCE Speciality Conference. Denver, Colorado, April.Google Scholar