Solving slope stability issues is a complex endeavour that must respect the potential failure mechanisms in each case; it is therefore insufficient to rely on a on a single aspect of the design such as numerical modelling.
“Numerical models are certainly a vital tool in the belt of the designer, but slope design requires models that are based on a thorough understanding of all of the inputs that go into the geotechnical model,” said Rob Armstrong, director, partner and principal geologist (geotechnical) at SRK Consulting (South Africa). “It is important to integrate the insights of various disciplines, which generally requires a team of multiple specialists.”
Such a team will allow for the development of an implementable slope design which also takes into account the intricacies of operational risk management and project financing cycles. The work involved would include engineering geophysics, structural geology, unmanned aerial vehicle (UAV) data collection for geotechnical studies, geostatistics and geohydrology.
Complexities of each site
“Input from all these professionals can generate comprehensive and fit-for-purpose geotechnical models that accommodate the complexities of each site,” he explained. “Among the key areas that need to inform these models are geology, geological structure, weathering, alteration, groundwater and geomechanical properties.”
He also pointed out that not every slope needed a detailed geotechnical model, and that a depth of experience is required to discern when it is required.
“Once an integrated geotechnical model is finalised, slope designers use this information to guide stability analyses,” he said. “With the help of advanced numerical modelling, if necessary, they use the model to analyse the actual mechanisms of failure – and to develop a practical, minable design.”
Importantly, life-of-mine slope design should not end with a design report. Consultants often work with their clients’ operational teams to help implement the design, by updating and optimising the design as more is understood about the deposit and adjacent ground.
