Numerical modelling of underground and open pit interaction in a gold mine

Authors: He, K; Swarbrick, G; Sullivan, TD Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2025_68

Cite As:
He, K, Swarbrick, G & Sullivan, TD 2020, 'Numerical modelling of underground and open pit interaction in a gold mine', in PM Dight (ed.), Slope Stability 2020: Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 1031-1046, https://doi.org/10.36487/ACG_repo/2025_68



Abstract:
The Waihi Gold operation (OceanaGold) consists of a mining and milling complex located within the township of Waihi, approximately 125 km southeast of Auckland, New Zealand. Mining at Waihi started in 1878 and comprised both underground mining (1878 to 1952) and open cut mining (1988 to present). The Martha Mine and its immediate environs have experienced a very long period of deformation and subsidence due to the historical underground mining. This study contains an assessment of the potential impacts of the proposed Martha Underground mine on the stability of proposed Martha Phase 4 pit. A 3D numerical model is developed by considering both historical and proposed underground and open cut mining. Caving affected rock mass zones around a planned historical underground caving operation, which has been incorporated into the model. The developed 3D model predicts a response to Martha Underground that is aligned with the experience and previous performance of the Martha Pits in terms of magnitude, location and distribution of movements. Sensitivity analyses were undertaken to investigate the effect of several input parameters used in the study.

Keywords: underground mining, open cut mining, caving zones, numerical modelling

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