Approach to groundwater and pore water pressure modelling for different geotechnical conditions in open pit slope stability analysis

Authors: El-Idrysy, H Download Paper

DOI https://doi.org/10.36487/ACG_rep/1308_27_Idrysy

Cite As:
El-Idrysy, H 2013, 'Approach to groundwater and pore water pressure modelling for different geotechnical conditions in open pit slope stability analysis', in PM Dight (ed.), Slope Stability 2013: Proceedings of the 2013 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 433-443, https://doi.org/10.36487/ACG_rep/1308_27_Idrysy



Abstract:
This paper presents two feasibility case studies related to groundwater modelling for pit slope stability studies at a diamond mine and a gold mine. While both open pit mine projects had a target final pit depth of about 450 m the impacts of groundwater conditions on the slope stability analyses are very different. The former required very detailed analysis and simulation of pore water pressure whilst at the gold mine, both groundwater flow and pore water pressure had limited impact on the slope stability assessment. The two case studies demonstrate that pore water pressure does not always significantly influence the stability of the pit slopes and that it is essential to identify the key controlling factors for slope stability before embarking on detailed modelling of pore water distribution. However, when pore water pressure and groundwater flow are identified as controlling factors due to geotechnical setting, extensive numerical modelling of groundwater flow is required to optimise a dewatering/depressurisation system that achieves the required Factor of Safety (FS) from pit slope stability analyses. A fully integrated numerical modelling analysis of pore water pressure and geotechnical slope stability is an intensive, iterative exercise but the result of such work is very rewarding in terms of optimising pit slope angles.

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