Engineering geological models in open pit slope engineering

Authors: Eggers, MJ Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2335_0.03

Cite As:
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



Abstract:
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

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