Complexity of Slope Stability
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- Created: Thursday, 28 August 2025 15:13
- Written by R. Armstrong

The South African mining industry is well known for the advancements in underground, especially ultra-deep, mines. But it has also made significant contributions to open pit mining and the stability of slopes. The SAIMM hosted a symposium on slope stability as early as 1970 (book S2 in the symposium series), which was conceptualised by the SAIMM because open pit mines were getting bigger and deeper, and the sharing of knowledge and experience from the industry was required. Over 300 local and international delegates attended the symposium, including technical, industry, and academic leaders in open pit mining and rock mechanics.
Incidentally, two of the speakers would go on to found two international mining consulting firms. Again, recognising that pits were being planned much deeper than ever before, The SAIMM planned the first International Symposium on Stability of Rock Slopes in Open Pit Mining and Civil Engineering in 2006, which has since been held 10 times in 8 different countries (now informally referred to as simply The Slopes Conference). This symposium was again organised by the SAIMM in 2015. This special edition of the journal serves as a further commitment to the development of the science and engineering of rock slopes, with the very high response of papers dealing with some interesting and pertinent developments. Topics covered include: slope stability analyses, groundwater interactions with slopes, forecasting of failure, detection of underground cavities, and the back analysis of a very large slope failure.
Significant developments have taken place in the last two decades in monitoring and numerical modelling of rock slopes. These often overshadow the importance of understanding the actual mechanics of big slopes, and how to reliably design them. Many advances in technology have provided the tools to aid in this, but there is a long way to go in understanding the complex interplay of the geological complexity (including varying rock types, geological structure, alteration, and weathering), complex groundwater systems (often grossly over simplified), strength properties, appropriate failure criteria, slope geometries, blasting, et al. These complexities are impossible to include in any single analysis or model, so the design and understanding of large slope behaviour still require contextualising multiple over-simplified models and determining how their interaction results in the limitation of slope equilibrium. Furthermore, how to manage all of that in the implementation of big slopes. This complexity means that slopes require the inputs from many specialists and an understanding of the limitations of their science and models. So much more is needed in the development of rock slope engineering.
R. Armstrong
Journal Comment
In the course of our engineering work on mining and metallurgical plants we are often called upon to evaluate the merits of different choices in process flowsheets, operating parameters and philosophies, raw material selection, and many others. The phenomenological complexity of the minerals industry usually means that each of these aspects is parameterised by a large number of variables, and there are also strong coupling effects between them – one changes a feed-rate setting here, and even though it fixes the immediate production problem over here, it also affects several other things over there in ways that one did not expect.
Just a couple of years ago the outgoing Chairman of the SAIMM Editorial Board, Dave Tudor, suggested that, as a previous metallurgical colleague, I should join the Board. Although I have been a member of the Institute for many years and was a previous Chairman of the Free State Branch, my knowledge of the management of the Institute was limited to attending some excellent schools and studying relevant journal papers.
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The mining industry is an exciting space, where the convergence of environmental stewardship, socio-economic responsibility, and technological innovation is reshaping the way we approach mine closure. As we navigate this complex landscape, the importance of mine closure planning is becoming more and more pronounced.
As the incoming President of SAIMM, I have been reflecting on my 34-year career in the mining industry and the lessons I have learned; lessons I can leverage to lead SAIMM and support the industry during my tenure. Writing this month’s journal comment provides an opportunity to share part one of some of these insights.
Mining has always been about more than just extracting minerals from the earth. It is about securing the future, balancing economic imperatives with environmental responsibility, technological innovation, and the well-being of those who power this industry. As we move forward, we must ask ourselves: are we truly mining with the future in mind?
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The mining engineering departments at the various South African tertiary institutes are responsible for producing the next generation of tech-savvy mining engineers. It is well known that it is an ongoing battle for these departments to attract top students. The problem is not unique to South Africa, however. Mining Digital reported earlier this year that mining is no longer seen as a popular career choice and enrolment in mining engineering courses decreased by 63% in Australia since 2014. The Mining Industry Human Resources Council of Canada found in a survey that 70% of the younger generation said they would not consider a career in mining and this was the highest proportion of all the industries included in the survey. This problem is even more complex in South Africa and addressing it will require a multi-pronged approach.