Open Access
M. Affam
P. Newton
- Associate Professor Geological Engineering, University of Mines and Technology (UMaT) Tarkwa Ghana
- Geological Engineering University of Mines and Technology (UMaT) Tarkwa Ghana
Abstract
Current approach to pit-wall analysis tends to separate designs into distinct categories. The first consideration involves analysis of slope in which discontinuities actively participate in the failure mobilization. The second involves design analysis of non-structural controls which could results in a wide range of failure mechanisms. The third and the least sought for approach is the economic assessment of the slope design which could render optimized pit slope and the bench face angle scenarios economic or otherwise. The sensitivity of the third consideration has become imperative in the face of depleting pit reserves as any positive turn over in the economic analysis could revive distress mine operations. A typical operating pit sited west of Ghana’s metalogenic province which was near collapse due to ore depletion was re-designed through steepening of the slopes to expose more resource. Geotechnical, window and photogrammetry mappings were carried to augment the historical data available. Several numerical analytical tools were also employed to model the pitwall angles. Four steeper slopes were designed from the current BFA of 65° to 70°, 75°, 80° and 85°. This was done to assist in stability, reduce stripping ratio and improve cash flow. The results indicated that discontinuities steeply oriented towards east direction could make the slope highly susceptible to planer and toppling failures The studies concluded that it may not be feasible to steepen BFA from the current base angle due to the predicted steeper angles as a results of overall slope instabilities even though the potential economic benefit is substantial. If steepening would be considered, major modifications of slope geometry; rock improvement, extensive slope monitoring and a good groundwater control management mechanism may be required.
Keywords: Birimian, auriferous, pitwall, instability, failure, economic analysis, Batter face angle
[This article belongs to International Journal of Geological and Geotechnical Engineering(ijgge)]
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References
1. Dampers GD, Seymour CRW, Jenkins PA. A new approach to assess open pit Slope stability International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Vancouver, Canada; 2011. p. 81–92.
2. Duncan CW, Christopher WM. Rock Slope engineering, civil and mining. 4th ed; 2004. Press S. New 228 pp.
3. Kesse GO. The mineral and rock resources of Ghana. Rotterdam, Netherlands: A. A. Balkema Publishers; 1985. p. 5–13.
4. Griffis RJ, Kwasi B, Akosah FK. Gold Deposit of Ghana, Graphic Evolution Ltd., 160 Saunders Rd, Ontario, Canada, LAN 9A4, 438 pp.
5. David S, Danny BS. Collecting and Using Structural Data for Slope Design. Society of Mining, Metallurgy and Exploration, 8307 Shaffer Parkway Littleton Co. 2002;80127:31–43.
6. Braja MD. The principles of geotechnical engineering. 6th ed. Toronto, Canada: Nelson Publishing Division of Thomson ltd; 2006. 593 p.
7. Bieniawski ZT. Engineering rockmass classifications. New York: Wiley; 1989. 251 p.
8. Hoek E, Carranza-Terres C, Corkum B. Hoek-Brown failure criterion. Proceedings of the 5th north American rock mechanics symposium. 2002 ed. In Mining and Tunnelling Inovation and Opportunity. Vol. 1. Toronto: University of Toronto Press; 2002. p. 267–73.
9. Laubscher DH. A geomechanical classification system for the rating of Rockmass in mine design. J West Afr Inst Min Metall. 1990;90 No. 10:257–73.
10. Stead D, Eberhardt E, Benko B. Advanced numerical techniques in rock Slope stability analysis-applications and limitation. Davos, Switzerland; 2001. p. 615–24.
11. Hudson JA. Rock Engineering Systems. Publi Ellis Harwood Ltd, England 185. pp; 1993.
International Journal of Geological and Geotechnical Engineering
| Volume | 7 |
| Issue | 1 |
| Received | November 26, 2020 |
| Accepted | January 20, 2021 |
| Published | January 20, 2023 |