de Bruyn, IA 2021, 'Building useful geotechnical models', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 37-50, https://doi.org/10.36487/ACG_repo/2135_0.04
(https://papers.acg.uwa.edu.au/p/2135_0.04_de Bruyn/)
Abstract: The success of any geotechnical design is dependent on the geotechnical model used in the design assessments. No matter the methodology adopted, the budget allocated, or the expertise assembled for the design analyses, an unsuitable geotechnical model will result in a sub-optimal outcome or misleading results. The nature of any geotechnical model must be dependent on the type, amount, and spatial distribution of the information available and the purpose for which the model is constructed. A geotechnical model for an open pit must allow for the generation of slope design parameters that are most appropriate for the geotechnical environment, taking into account the dominant mode/s of failure, the level of confidence in the data and acceptable levels of risk. It may require a significant amount of evaluation, interpretation, and judgement to develop a model that is fit-for-purpose, even for one that appears simple. It is better for it to be approximately ‘right’ than precisely ‘wrong’!
This paper discusses the conception and development of appropriate geotechnical models for slope design. It considers the types of information available, the level of study, the shape of the excavation, controlling failure mechanisms, and uncertainties. It discusses how a model can be spatially defined and how the data can be best used to characterise each zone. The lithology, alteration, structural and hydrogeology models that contribute to the geotechnical model, and the likely slope failure mechanisms are important in selecting appropriate software or analysis methods that should be employed for slope design analyses. In this context, typical pitfalls in geotechnical models are examined.

Keywords: geotechnical model, numerical model, characterisation, stability analysis, slope design