Investigating the different support methods for various geological structures encountered in hard rock mining within the Eastern Limb of the Bushveld Igneous Complex South Africa

Abstract

Mining operations throughout the Bushveld Igneous Complex faces challenges in regards to the safe support of geological structures. Falls of Ground pose a massive risk to safety and production of any underground mining operation and programmes to eliminate falls of ground must be effective and implementable. The investigation will focus on the geological structures found across hard rock mines in the Eastern Limb of the Bushveld Igneous Complex, South Africa. How these features are identified, recorded and supported. Geological structures such as dykes (magnetic and non-magnetic), faults, joints, reef rolls, thrust faults (domes) and potholes are all geological features found in underground workings within Eastern Limb mining operations. Each of these structures pose a risk to the safe working and productive mining of a mining operation if left under/un- supported. Geological structures occur in underground workings, some panels contain multiple structure’s that call for complex support recommendations and procedures. Mining panels within the investigation and monitoring period are classified according to the geological features they contain and divided in Green, Yellow and Red panels, with the change in colour representing the ground conditions of that panel and the subsequent team that need to issue recommendations. Green panels are safe for work with no major geological structures that pose a risk to underground workings, normal mining with normal support according to the support standard and procedure can commence. Yellow panels have geological features that were identified and marked but are of such a nature that the Team Leader, Miner and Shift Supervisor can decide on support recommendations in addition to the standard support system. Red panels will be the focus of the investigation, these panels have been rated according to the complicating geological structures they contain. Recommendations for underground panels with complex geological features are made by a team of specialists comprising of a Geologist, Strata Control Officer, Mine Overseer and Shift Supervisor. The geological structures are mapped, recorded and studied where after recommendations are agreed upon. The investigation focusses on the recommendation issued to support various geological features and their continued monitoring throughout a 1 year period and whether the recommendations are adequate. Complex geological structures with support recommendations were monitored and failure or change in ground conditions were identified to determine whether recommendations were sufficient. From the monitoring it is clear that the majority of geological features are adequately supported and continued to be safe for underground work to take place throughout the monitoring period. In areas where failure, change or falls of ground occurred within the study period, it was investigated and found to be due to human factors or external factors and not due to the physical support of geological features. External factors include a change in ground conditions since the visit (water presence where there was no water present when recommendations were issued), incorrect or incomplete installation of support and the incorrect identification of a geological feature. The success of supporting geological features depend on the correct implementation of the support recommendations issued to support complex geological features within underground workings. The system was monitored during the investigation period and found to be efficient and accurate in identifying and supporting complex geological features. The success rate of supporting geological features by means of this system is effective and easily implementable from operation to operation. The complex geological features that were supported using the recommendations issued by the investigation team are safely supported and the system used to support these features is highly effective.