The Department of Mining Engineering in the University of Pretoria’s Faculty of Engineering, Built Environment and Information Technology congratulates Prof Francois Malan on his promotion to full professor. In his inaugural address, delivered virtually on 29 July 2021, Prof Malan discussed rock engineering research as a prerequisite for sustainability and growth in the mining sector.

“Everything we depend on in our daily lives is either made from minerals or relies on minerals for its production,” says Prof Malan. Future innovations would not be possible without the support of the mining industry. “From renewable energy to electric vehicles and commercial space travel, none of these initiatives would be viable without an increased source of materials, which need to be mined.”

South Africa has a proud history of mining. In 2020, it contributed R361.6 billion to the country’s GDP and employed 451 427 people. The country’s huge mineral endowment is ranked very highly globally in terms of Platinum Group Metals (PGM), chrome and manganese reserves. This, however, represents a decline in terms of contribution to GDP, gold production and employment relative to the situation a decade ago. Prof Malan believes that rock engineering research can help turn this situation around, paving the way for sustainability and growth in the mining sector.

As a discipline in which Prof Malan is a renowned specialist, rock engineering examines the mechanical behaviour of rock in relation to the physical environment. It also focuses on methods to determine the strength of underground pillars, and hence ensure the safety of mineworkers. According to Prof Malan, South Africa’s economically viable underground ore bodies have a unique tabular structure. It has long been acknowledged that no other mining region of economic significance has ore bodies of a similar geometry, and no country outside South Africa can find a solution to this problem. Home-grown research is therefore essential to understand and improve the exploitation of the country’s mineral reserves.

Looking back at the historic development of rock mechanics in South Africa, Prof Malan observed that it was only after a series of unfortunate events that it became evident that a research-based approach was necessary to develop mine design criteria that would ensure that the ore can be mined safely. These events included several rockbursts, as well as the devastating Coalbrook Colliery disaster of 1960, the worst mining accident in South Africa’s history that involved the collapse of 900 pillars almost 180 m underground and led to 437 miners being trapped underground.

The earliest rock engineering research was focused on investigating whether the stress around mining excavations could be analysed mathematically. Major breakthroughs included developing an empirical coal pillar strength formula and adopting elastic theory to describe rock mass behaviour in deep gold mines. This led to the development of popular design concepts and theories, some of which are still in use today. The adoption of elastic theory was particularly important as it made stress simulation possible. A solid foundation was laid by pioneers such as Evert Hoek, ZT Bieniawski, MDG Salamon and NGW Cook, which enabled modern techniques to be further developed.

Prof Malan’s areas of research expertise include numerical modelling, pillar behaviour and mine design criteria. His current research interests include the inelastic numerical modelling of tabular excavations, and simulating pillar behaviour and pillar strength. He is currently exploring the use of a limit equilibrium model to approximate the time-dependent relationship between reefs’ normal stress and parallel stress components. This research emanated from the realisation that time-dependency could not be simulated using elastic theory, and even earlier attempts to simulate the fracture zone with viscoelastic theory only proved to be partially successful.

Using the limit equilibrium model, Prof Malan was able to simulate closure data, which provided a much better approximation of actual underground closure. This method allows for the simulation of mining increment size and mining rate. However, it is difficult to calibrate the large number of parameters using this model. This highlights the need for ongoing closure monitoring in underground slopes. An important element of Prof Malan’s work is the development of a pillar strength formula that will be effective in South Africa’s bord and pillar mines as the depth increases.

Several other studies are being undertaken by the Department’s Rock Engineering Research Group, which Prof Malan heads. One such study entails examining pillar failure due to weak layers. This phenomenon has led to some large-scale mine collapses. Another study entails the design of rockburst support, since seismic-induced rockbursts are still a big problem in South Africa’s deep gold mines. A new-generation mesh and thin spray-on liners are currently being studied to improve aerial support in the stopes.

Close collaboration has been established with the mining industry, especially with Harmony Gold, Northam Platinum and Impala Platinum. Prof Malan is grateful for this continued industry support, which assists in the development of a corps of postgraduate researchers to ensure the sustainability and growth of the industry.

Click here to view Prof Malan’s inaugural address.

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