Eggers, MJ 2023, 'Engineering geological models in open pit slope engineering', in PM Dight (ed.), SSIM 2023: Third International Slope Stability in Mining Conference
, Australian Centre for Geomechanics, Perth, pp. 35-54, https://doi.org/10.36487/ACG_repo/2335_0.03
The key to the successful design and management of slopes in mining is in understanding the geological controls on rock behaviour when it is stressed by surface excavation, pore pressure changes and external forces such as seismic loads. The purpose of this geological approach to rock slope engineering is to enable more accurate and reliable prediction of stability conditions when undertaking slope design at any stage of the mine life cycle, from feasibility studies to mine closure.
There is a trend in recent practice to concentrate the geotechnical model development towards rock mass classification and how this rock mass model can be used in stability analysis. The geological component of the geotechnical model is often neglected or directly lifted from the resource model. As the resource model has an objective to predict mineralisation and grade, it is typically not focused on areas in the deposit of geotechnical importance. These factors can sometimes take attention away from the main features of the geotechnical model that are driving behaviour and failure mechanisms, in particular structure, geological influence on change in rock mass condition, and groundwater. The role of the engineering geological model (EGM) is to ensure all the key geological controls on rock behaviour and performance are adequately identified and evaluated to inform the analysis, design and management of slopes.
The paper describes the conceptual and observational types of EGMs and how they relate to the mine design life cycle. The geology, structure, rock mass and hydrogeology components of the EGM are summarised and described in relation to development of the model, including the engineering geological description, model geometry and visualisation, and geotechnical characterisation of engineering properties and parameters. The importance of conceptualisation is emphasised, and the notion of EGMs as both a knowledge framework and ideology are summarised as the preferred approach to more accurate development of geotechnical models for mine design.
Keywords: engineering geological models, conceptual models, observational models, regional geology, structure, rock mass, hydrogeology, characterisation, model geometry, visualisation, geotechnical parameters, conceptualisation, knowledge framework
Baynes, FJ, Parry, S, & Novotny, J 2021, ‘Engineering geological models, projects, and geotechnical risk’, Quarterly Journal of Engineering Geology and Hydrogeology, vol. 54,
Baynes, FJ & Parry, S 2022, ‘Guidelines for the development and application of engineering geological models on projects’, International Association for Engineering Geology and the Environment (IAEG) Commission 25 Publication No. 1.
Beale, G & Read, J 2021, Guidelines for Evaluating Water in Pit Slope Stability, CRC Press, Boca Raton.
Bieniawski, ZT, 1989, Engineering Rock Mass Classifications: A Complete Manual for Engineers and Geologists in Mining, Civil, and Petroleum Engineering, John Wiley & Sons, Hoboken.
Bond, CE 2015, ‘Uncertainty in structural interpretation: lessons to be learnt’, Journal of Structural Geology, vol. 74, pp. 185–200,
Eggers, MJ & Casparis, DL 2007, ‘Pit slope design in Pilbara iron deposits - Deposit A West Angelas, Western Australia’, 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. 463–476,
Eggers, MJ 2016, ‘Engineering geological modelling for pit slope design in the porphyry copper-gold deposits of Southeast Asia’, in PM Dight (ed.), APSSIM 2016: Proceedings of the First Asia Pacific Slope Stability in Mining Conference, Australian Centre for Geomechanics, Perth, pp. 49–82,
Eggers, MJ 2022, ‘EGMs for rock engineering projects’, in FJ Baynes, & S Parry (eds), Guidelines for the Development and Application of Engineering Geological Models on Projects. IAEG Commission 25, Publication No.1.
Fookes, PG 1997, ‘Geology for engineers: the geological model, prediction and performance’, Quarterly Journal of Engineering Geology and Hydrogeology, vol. 30, no. 4, pp. 293–424,
Fookes, PG, Baynes, FJ & Hutchinson, JN 2000, ‘Total geological history: a model approach to the anticipation, observation and understanding of site conditions’, Proceedings of GeoEng2000, an International Conference on Geotechnical & Geological Engineering, Technomic Publishing Company Inc., Pennsylvania, pp. 370–460
Hawley, M & Cunning, J 2017, Guidelines for Mine Waste Dumps and Stockpile Design, CRC Press, Boca Raton.
Knill, JL 2003, ‘Core values: the first Hans-Cloos lecture’, Bulletin of Engineering Geology and the Environment, vol. 62, pp. 1–34.
MacKean, R 2022, ‘Rock mass models for design of excavations in structurally controlled rock masses’, in FJ Baynes & S Parry (eds), Guidelines for the Development and Application of Engineering Geological Models on Projects. IAEG Commission 25, Publication No.1.
Martin, D & Stacey, P 2018, Guidelines for Open Pit Slope Design in Weak Rocks, CRC Press, Boca Raton.
McMahon, BK 1985, ‘Australian Geomechanics Society E.H. Davis Mineral Lecture, geotechnical design in the face of uncertainty’, Australian Geomechanics Journal, vol. 10, pp. 7–19.
Parry, S, Baynes, FJ, Culshaw, MG, Eggers, M, Keaton, JF, Lentfer, K, Novotny, J & Paul, D 2014, ‘Engineering geological models – an introduction: IAEG Commission 25’, Bulletin of Engineering Geology and the Environment, vol. 73, no. 3, pp. 689–706,
Read, J & Stacey, P, 2009, Guidelines for Open Pit Slope Design, CRC Press, Boca Raton.
Sharon, R & Eberhardt, E 2020, Guidelines for Slope Performance Monitoring, CRC Press, Boca Raton.
Sullivan, TD 2010, ‘The geological model’, in AL Williams, GM Pinches, CY Chin, TJ McMorran & CL Massey (eds), Geologically Active, Proceedings of the 11th Congress of the International Association for Engineering Geology and the Environment, pp. 155–170.
Woodall, R 1985, ‘Limited vision: a personal experience of mining geology and scientific mineral exploration’, Australian Journal of Earth Sciences, vol. 32, pp. 231–237