The SANIRE Coalfields branch held its year-end function on the 02nd of December 2016 at the Tweefontein Recreation Club, in eMalahleni. This marked one of the very first events since the new branch committee was elected in February. A number delegates, consisting of practitioners, consultants and suppliers, came from various parts of the country to enjoy this prestigious event. The total number of delegates in attendance was 47 and the event was sponsored by Videx and Rocbolt technologies.

As a norm of the branch, the essential part of an event of this magnitude comprises the technical presentations which always expose the practitioners to an opportunity to keep abreast with the latest developments. The highlight of this year’s technical presentation was from Professor Nielen van der Merwe. His presentation was simply a summary of the groundbreaking work that he has done thus far on the Probability of pillar survival (POS) and Pillar Life Index (PLI). A takeaway from this presentation is the link between these concepts through the safety factor. “Requirements can now be set for the POS of a pillar system, coupled with a required POS at any time in the future” said Nielen. He further emphasized that the acceptable limits of probabilities of failure for various categories of protection should be determined by agreement between different stakeholders. This three-tier method of stability evaluation for coal mines brought some sense of relief to the coal practitioners on how to integrate and implement these concepts. This work has since been published in the December 2016 SAIMM journal.

Mr Prince Mulenga from SRK Consulting brought yet another interesting topic when he presented on the Coal Squat Pillar design using numerical modelling. This included a detailed comparison of the different pillar strength formulae available in the industry with the numerical modelling results of the squat pillar and highlighted very crucial aspects for future research in this area. The following conclusions were drawn from his research:

  • Pillar peak strength is dependent on the peak and residual friction angle used in the model.
  • The strain at which the peak friction angle is dropped to residual friction has an effect on the strength of the pillars.
  • The brittle-ductile transition was found to depend on the residual friction angle.

Coal-based researchers are in agreement that there is a need to expand the life of the Highveld and Witbank Coalfields, respectively. One other method to do this is the extraction of the old coal pillars through an opencast mining method, but this is not without its own challenges.

Dr Michael van Schoor from CSIR captivated the delegates with his presentation that was aimed at introducing various ways of locating the Old Shallow Coal Pillars, which was one step towards resolving some of the challenges inherent in mining of the old coal pillars. It was to the delegates’ disappointment that there is currently no surface technique available for locating these old pillars. He however suggested a number of other possible options for locating pillars, such as Robots.

Mr Lance van Steel from MapTek left the delegates wanting more when he touched on the technological side of Rock Engineering. His presentation was on the Geotechnical Stability Solution for Open Pit and underground, which was more on the geotechnical data derivation and analysis, as well as monitoring of the workings.

After such an intriguing event, the delegates departed for a mouth-watering sit-down barbeque lunch, with anticipation for the great year ahead. Needless to say, some remained for beers and networking.