Geological safety and optimisation in mining operations: towards a new understanding of fracture damage, heterogeneity and anisotropy.

The current economic viability and longevity of open cast and underground mines that are extracting strategically important natural resources are limited in many areas by complex geology: faults, rock heterogeneities and discontinuities. This project has assembled an international team to integrate geological complexity, laboratory testing, and numerical modelling in order to develop better mapping and prospecting tools for minerals such as Copper and Lithium. Such resources are essential for the modern economy, which, as energy switches from fossil fuels to sustainable 'green' technologies, is increasingly reliant on high efficiency electric motors, 'smart' power grids, and batteries for energy supply and storage. As such, advanced motors and batteries rely on a suite of metals and minerals including Lithium (for batteries), Copper (for power transmission and motor windings), and Neodymium, used for high-power motors in space-critical applications ranging from hard-disk drives to electric vehicles. However, extracting such elements in an economically viable, safe, and sustainable manner remains challenging. Chile hosts some of the largest Copper mines in the world, where these metals are extracted using a range of methods from deep mines (up to nearly 2km depth) to large open pit designs. Similar operations exist - or are planned - for Lithium mining in other countries including Australia (Talison) and Canada (La Corne).

Managing the rock 'mass' that hosts these (and other) minerals with the aim of extracting the ore in a sustainable and economic manner is the focus of all mining operations. Furthermore, with the continuing shift to electric power storage and transmission driving increased demand for Copper, Lithium and other resources, the requirement for optimal extraction is likely to become ever more important. However, large volumes of natural rock contain a plethora of natural fractures - or heterogeneities - that makes safe mineral extraction a challenge. This includes hidden faults in the rock mass, veins of low strength, and 'layers' of high strength rocks interbedded within the target zone. Taken together, these heterogeneities make the task of constructing a 3D representation of mine workings (needed for optimal extraction) very difficult, particularly as the overall efficiency of the mine requires steep slopes, yet these are more likely to be unstable when the various heterogeneities above are factored in. Importantly, may standard methods for estimating the stability of steep rock slopes, such as the well-known (but very simple) Factor-Of-Safety approach, cannot (by design) incorporate such heterogeneities.

The aim of the GeoSafe project is to combine the expertise of the Rock Mechanics Laboratory at the University of Portsmouth and the School of Mining at Pontificia Universidad Católica de Chile into a new collaboration to better understand the mechanics and physics of heterogeneities across scales from centimeter to tens of metres. We will achieve this by co-developing new numerical models, calibrated by laboratory and field datasets, to understand how small scale (cm to meter) heterogeneities influence large-scale rock stability in both open-cast and underground mines. These new data and models will allow us to replace the standard Factor-of-Safety approach traditionally used to assess the stability of rock masses by a new risk-based numerical model (RBM) incorporating heterogeneities via a fractal-based scaling parameter. Ultimately, this will improve the safety (both physical and environmental) and the economic success of these operations, with particular emphasis on safely extracting the minerals needed in the global renewable energy economy.