Beer, AJ & Morrongiello, MR 2007, 'Wall Optimisation - A Case Study From the Fimiston Open Pit, Kalgoorlie Consolidated Gold Mines', 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. 403-415, https://doi.org/10.36487/ACG_repo/708_26
(https://papers.acg.uwa.edu.au/p/708_26_Beer/)
Abstract: During 2006, Kalgoorlie Consolidated Gold Mines’ (KCGM) Geotechnical Section led a wall optimisation 
project for the Fimiston Open Pit. The 2006 stage of the project was aimed at bringing this increase into the 
‘probable reserve’ category.  The 2006 project has also identified the further studies which will be necessary 
to move this reserve increase up to the ‘proven’ category. 
The project re-assessed assumptions made in a 1989 report, based on near-surface exposures. Observed pit 
wall structures and behaviour led to the decision to re-evaluate the optimum wall angle. For the first stage of 
the project, mainly existing data has been used, and primarily rock mass property data collected since 1990, 
but also structural data from the mapping of the old underground workings. The results from a major 
groundwater modelling project provided information as to the location of the phreatic surface which was 
used as an input to the modelling. 
For the 2006 stage of the project, probability of failure was calculated using Rosenblueth’s (1975) Point 
Estimation Method to pick values for rock mass parameters. These values were then used to generate shear-
normal functions for the rock mass which provided input parameters to the SLIDE™ package (Rocscience, 
2005), the probability of failure being obtained from the mean and standard deviation of the factors of safety 
so derived.