Authors: Elmo, D; Yan, M; Stead, D; Rogers, SF

Purchase Paper

Cite As:
Elmo, D, Yan, M, Stead, D & Rogers, SF 2007, 'The Importance of Intact Rock Bridges in the Stability of High Rock Slopes - Towards a Quantitative Investigation Using an Integrated Numerical Modelling;Discrete Fracture Network Approach', in Y Potvin (ed.), Proceedings of the 2007 International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 253-266.

Download citation as:   ris   bibtex   endnote   text   Zotero


Abstract:
As large open pit rock slopes reach increasingly greater depths and more frequently involve interaction with underground mines the need to consider intact rock fracture becomes ever more important. This paper emphasizes the importance of brittle rock failure propagation through intact rock bridges in high rock slopes, with reference to both large open pits and their natural analogues, high mountain slopes. Quantification of discontinuity persistence and intact rock bridges within rock slopes is a critical component of rock slope research and requires not only the use of new data collection techniques but also data interpretation through rigorous fracture network analysis. Using probability density functions to represent discontinuity orientation, spacing and persistence, the Discrete Fracture Network (DFN) approach is shown to represent an ideal numerical tool with which to synthesise realistic fracture network models from digitally and conventionally mapped data. Integration of a DFN model with a hybrid geomechanics code that is able to model fracture propagation allows the simulation of the interaction between naturally occurring discontinuities and brittle fracture through intact rock bridges. Having discussed the applications and limitations of a 2-D discrete numerical approach, simulations are presented based on DFN models of a large conceptual rock slope and incorporating varied failure mechanisms. Simulations demonstrate the importance of considering both realistic fracture mechanisms and the ability to model complex failure paths involving sliding along discontinuities, dilation, and intact rock fracture. The paper concludes with a discussion on the definition of intact rock bridges for a 3-D analysis. Significant future challenges presented by the incorporation of inherently 3-D rock structures in large-scale numerical models are emphasised.

References:
Barton, N. (2002) Some new Q-value correlations to assist in site characterisation and tunnel design. Int. J. Rock Mech.
and Min. Sci. 39, pp. 185-216.
Bieniawski, Z.T. (1989) Engineering rock mass classification. John Wiley & Sons, New York, 251 p.
Cai, M., Kaiser, P.K., Uno, H., Tasaka, Y. and Minami, M. (2004) Estimation of rock mass deformation modulus and
strength of jointed hard rock masses using the GSI system. Int. J. Rock Mech. and Min. Sci. 41, pp. 3-19.
Dershowitz, W. and Einstein, H.H. (1988) Characterizing rock joint geometry with joint system models. Rock Mech.
and Rock Eng. 21, pp. 21-51.
Dershowitz, W.S., Lee, G., Geier, J. and Lapointe, P.R. (1998) FracMan: Interactive Discrete Feature Data Analysis.
Geometric Modelling and Exploration Simulation. User Documentation. Golder Associates Inc. Seattle,
Washington.
Dershowitz, W.S. and Herda, H. (1992) Interpretation of fracture spacing and intensity. Proceedings 32nd U.S. Rock
Mechanics Symposium, Santa Fe, New Mexico.
Diederichs, M.S. (2003) Rock fracture and collapse under low confinement conditions. Rock Mech. and Rock Eng. 36,
pp. 339-381.
Einstein, H.H., Veneziano, D., Baecher, G.B. and O’Reilly, K.J. (1983) The effect of discontinuity persistence on rock
slope stability. Int. J. Rock Mech. and Min. Sci. & Geomech. Abst. 20, pp. 227-236.
Elmo, D. (2006) Evaluation of a hybrid FEM/DEM approach for determination of rock mass strength using a
combination of discontinuity mapping and fracture mechanics modelling, with particular emphasis on modelling
of jointed pillars. PhD Thesis. Camborne School of Mines, University of Exeter U.K.
Elmo, D., Vyazmensky, A., Stead, D. and Rance, J.R. (2007) A hybrid FEM/DEM approach to model the interaction
between open-pit and underground block-caving mining. 1st Canada-US Rock Mechanics Symposium,
Vancouver. Taylor & Francis, London, Vol. 2, pp. 1287-1294, Golder Associates.
Golder Associates (2006) Fracman software suite. FracMan Technology Group (www.fracman.com).
Hoek, E.T., Carranza Torres, C. and Corkum, B. (2002). Hoek-Brown failure criterion - 2002 edition. In RocLab user’s
manual. Rocscience. www.rocscience.com
International Society of Rock Mechanics (1981) ISRM suggested methods for rock characterisation testing and
monitoring. E.T. Brown (editor) Imprint Oxford: Pergamon, 211 p.
Jennings, J.E. (1970) A mathematical theory for the calculation of the stability of slopes in open cast mines.
Proceedings Planning of Open Pit Mines, Johannesburg, pp. 87-102.
Mauldon, M. (1998) Estimating mean fracture trace length and density from observations in convex windows. Rock
Mech. and Rock Eng. 31, pp. 201-216.
Moffitt, K.M., Rogers, S.F., Beddoes, R.J. and Greer, S. (2007) Analysis of Slope Stability in Strong, Fractured Rock at
the Diavik Diamond Mine, NWT. Proceedings of 1st Canada-U.S. Rock Mechanics Symposium. Vancouver.
Rockfield Software (2007) ELFEN Version 3.8.9. Rockfield Software Ltd, Swansea, UK.
Rogers, S.F., Kennard, D.K., Dershowitz, W.S and van As, A. (2007) Characterising the in situ fragmentation of a
fractured rock mass using a discrete fracture network approach. Proceedings of 1st Canada-U.S. Rock Mechanics
Symposium, Vancouver.
Staub, I., Fredriksson, A. and Outter, N. (2002) Strategy for a Rock Mechanics Site Descriptive Model Development
and testing of the theoretical approach. SKB Report R-02-02. Golder Associates AB. SKB.
Stead, D., Yan, M., Elmo, D. and Coggan, J.S. (2006a) New developments in rock slope engineering: implications for
open pit slope design. Mining Geotechnics Session 2006 Canadian Geotechnical Society Conference.
Vancouver, Canada.
Stead, D., Eberhardt, E. and Coggan, J.S. (2006b) Developments in the characterisation of complex rock slope
deformation and failure using numerical modelling techniques. Eng. Geology. 83, pp. 217-235.
Stead, D., Elmo, D., Yan, M. and Coggan, J.S. (2007) Modelling brittle fracture in rock slopes: experience gained and
lessons learned. Proceedings International Symposium on Rock Slope Stability in Open Pit Mining and Civil
Engineering. Perth, Australia.
Yan, M., Elmo, D. and Stead, D. (2007) Characterisation of step-path failure mechanisms: A combined field based-
numerical modelling study. Proceedings 1st Canada-U.S. Rock Mechanics Symposium. Vancouver.
Zhang, L. and Einstein, H.H. (1998) Estimating the mean trace length of rock discontinuities. Rock Mech. and Rock
Eng. 31, pp. 217-235.
Zhang, L. and Einstein, H.H. (2000) Estimating the intensity of rock discontinuities. Int. J. Rock Mech. and Min. Sci.
37, pp. 819-837.
The Importance of Intact Rock Bridges in the Stability of High Rock Slopes ― Towards a
Quantitative Investigation Using an Integrated Numerical Modelling; Discrete Fracture Network Approach D. Elmo, et al.
266 Slope Stability 2007, Perth, Australia




© Copyright 2019, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
Please direct any queries or error reports to repository-acg@uwa.edu.au