Developing a Numerical Model for a Deep Open Pit

Authors: Hamman, ECF; Coulthard, MA Download Paper

DOI https://doi.org/10.36487/ACG_repo/708_12

Cite As:
Hamman, ECF & Coulthard, MA 2007, 'Developing a Numerical Model for a Deep Open Pit', in Y Potvin (ed.), Slope Stability 2007: Proceedings of the 2007 International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 225-237, https://doi.org/10.36487/ACG_repo/708_12



Abstract:
Sunrise Dam Gold Mine consists of the Cleo open pit and extensive underground development from where the extraction of flat and steep dipping tabular orebodies have commenced in the western wall of the pit. The ultimate open-pit dimensions will be approximately 2100 m long, 1200 m wide and 440 m deep. The pit is geotechnically demanding with mining exposing new challenges on each bench due to the varying lithologies and complex structural geology. In 2003, a detailed structural mapping programme was started to identify potential problematic mine-scale structures, and to evaluate the properties of the main joint sets observed in the pit. A number of strength testing programmes were completed each year to establish a rock mass property database. The data from both these programmes formed the basis of the geotechnical model used to select the design sections to be analysed using numerical analysis techniques. Four design sections were selected for the western wall to evaluate the slope behaviour using the program UDEC. The UDEC models for each section incorporated an explicit representation of the major joint sets within the rock mass, and also treated the rock material strength via the Hoek-Brown criterion. Parametric studies were performed, considering two cases of joint friction angle and both upper and lower estimates for rock material UCS. Each model consisted of an equilibration of the pre-mining system, then excavation to the ultimate pit in three stages. Finally, rock and joint strengths were progressively reduced for the final stage of mining, to provide estimates of the factor of safety (FoS) of the west wall slope.

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