Ulrich du Preez investigated the rock-machine interface for narrow-reef hard-rock mining, where conventional drill-and-blast cycles remain dominant and practical mechanical cutting requires a much better understanding of UG2 reef behaviour.
Building the experimental capability
Ulrich designed and manufactured a laboratory linear cutting machine rather than relying only on published cutting data. The machine incorporated a calibrated load-cell system and enabled controlled changes to cutting depth and other operating parameters. It was first commissioned on sandstone so that the mechanical system and measurement chain could be checked before testing heterogeneous UG2 reef samples.
Experiments and modelling
The study combined physical cutting tests with finite-element modelling in Ansys LS-DYNA, using a continuous surface cap material model. It investigated how rock properties, element choices, contact parameters and boundary conditions affected predicted forces and fragmentation.
Sandstone and UG2 showed some similar trends, but the differences were important. Cutting depth had a stronger influence on UG2 results, while UG2 produced much finer fragments under conditions where sandstone produced larger chips. That fine material is operationally significant because powder-like fragments are difficult to clean from a narrow stope. Frequency analysis also found a clearer periodic force response in sandstone than in UG2.
Contribution and outcome
The work demonstrated why homogeneous sandstone cannot automatically be used as a design proxy for UG2. A numerical model could be calibrated for one cutting condition, but did not yet generalise reliably when the parameters changed—a clear direction for future model development.
Ulrich completed his MEng with distinction in 2024. The research produced both a dissertation and a peer-reviewed article, and left RAMMS with a physical test capability for continued rock-cutting research.