Narendranathan, S, Thomas, RDH & Neilsen, JM 2013, 'The effect of slope curvature in rock mass shear strength derivations for stability modelling of foliated rock masses', in PM Dight (ed.), Proceedings of the 2013 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering
, Australian Centre for Geomechanics, Perth, pp. 719-732.
In open pits the instability mechanisms are multifaceted involving; shearing along or over the asperities of the defect surface and/or block rotation at very low normal stresses. At higher degrees of confinement, shearing along or through asperities and block rotation including rock mass failure due to intact rock breakage can occur. It is common to have pit designs with varying profiles resulting in concave, straight and convex geometries. This difference in wall geometry would result in varying magnitudes of effective shear strength being mobilised. The contribution of the lateral confinement to the degree of shear strength mobilised is often overlooked in design. In this paper a case study will be presented, which compares the different slope performance outcomes within similar geotechnical conditions with the only variant being the slope geometry and the influence of lateral confinement. An algorithm is developed, based on observations from this site case study, linking the concavity of a slope face to the degree of (extra) shear strength mobilised. It is the authors intent that this algorithm can be used in a similar manner to which highway engineers use ‘curve-speed models’ to determine safe approach speeds for corners given a particular road curvature, (in our case pit slope concavity) and approach speed (rock mass characteristics). This relationship has been implemented for forward analyses at the mine in question; however the authors acknowledge that further work needs to be undertaken so as to ensure the validity of the relationship for generalised application.
Armstrong, R. and Stacey, T.R. (2003) A review of information on the influence of plan curvature on rock slope stability and its effect on the volume of wedge failures, in Proceedings 10th International Society for Rock Mechanics Congress – Technology Roadmap for Rock Mechanics, 8–12 September 2003, Johannesburg, South Africa, South African Institute of Mining and Metallurgy.
Barton, N.R., Lien, R. and Lunde, J. (1974) Engineering classification of rock masses for the design of tunnel support, Rock Mechanics and Rock Engineering, Vol. 6(4), pp. 189–236.
Bieniawski, Z.T. (1989) Engineering rock mass classifications, John Wiley & Sons, New York, 251 p.
Call, R.D. (1992) Slope stability, Society for Mining, Metallurgy and Exploration Mining Engineering Handbook, Vol. 1, pp. 881–896.
Förster, W. (1966) The influence of the curvature of open cuts on the stability of slopes in open-work mining, in Proceedings First Congress of the International Society for Rock Mechanics, 25 September–1 October 1966, Lisbon, Portugal, International Society for Rock Mechanics, Vol. 2, pp. 193–200.
Hoek, E. and Bray, J.W. (1981) Rock slope engineering, 3rd edition, Institute of Mining and Metallurgy, London, pp. 309–313.
Luton, R.J (1970) Rock Slope Chart from empirical Slope Data in Transactions, Society for Mining, Metallurgy and Exploration and The American Institute of Mining, Metallurgical and Petroleum Engineers, Vol. 247, No. 2, pp. 160–162.
McMahon, B.K. (1971) A statistical method for the design of rock slopes, in Proceedings of the 1st Australian – New Zealand Conference on Geomechanics, Melbourne, Australia, Vol. 1, pp. 314–321.
Rocscience Inc. (2012) Phase2 Finite Element Analysis for Excavations and Slopes software,
Stacey, T.R. (1973) A three dimensional consideration of the stresses surrounding open-pit mine slope, International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, Vol. 10, pp. 523–533.
Stacey, T.R., Yu Xianbin, Armstrong, R. and Keyter, G.J. (2003) New slope stability considerations for deep open pit mines, Journal of South African Institute for Mining and Metallurgy, Vol. 103, No. 6, pp. 373–389.
Sullivan, T.D. (1993) Understanding pit slope movements, Geotechnical instrumentation And Monitoring in Open Pit and Underground Mining, T. Szwedzicki (ed), Balkema, Rotterdam, pp. 435–445.
Zavodni, Z.M. (2000) Time-dependent movements of open-pit slopes, Slope Stability in Surface Mining, W.A. Hustrulid, M.K. McCarter and D.J.A. Van Zyl (eds), Society for Mining, Metallurgy and Exploration, Colorado, pp. 81–87.