Any bord and pillar platinum mine thrives on effective design of bords and pillars. Pillars have to be large enough to ensure safety and small enough to ensure economic and sustainable exploitation of the mineral resource. Consideration of span of the bords of the working area is also crucial to safe and economic design of the mining layout. This research makes a critical review of the current design approach so as to understand the contributors to pillar failure in a section of an underground platinum bord and pillar mine. The research focuses on the areas that have been plagued by bad ground and seeks to determine the suitability of the current design in such conditions with an objective to redesign the section so as to curb the consequences of pillar failure in the operation. At the core of this research is the detailed geotechnical data of the area that was studied. Making use of Rock Mass Classification (RMC) and other rock engineering techniques, the review indicates that the adopted design is not suitable for the ground conditions evaluated, thus confirming the problem’s origin. The safety factor analysis shows that the ground conditions in the area of study would pose a greater risk due to failure of pillars. The conditions, predominantly the closer joint spacing made the rock mass deteriorate in strength and quality thus the pillar size needed to be increased so as to maintain the required strength. This shows that the pillars in the study area are at a higher risk of failure hence motivating for the redesign process. This paper details the proposed redesign which, if implemented, is expected to see a reduced extraction ratio but will enhance stability and facilitate optimum mining operations.
Accurate pillar design and stability analysis are crucial to safe mining in a bord and pillar layout. This paper makes a critical review of the current bords and pillar design and layout at a platinum mine in Zimbabwe which has been affected by ground failure. The mine is located on the Great Dyke of Zimbabwe and exploits an orebody which is not deeper than 500m below surface for Platinum Group Elements (PGEs). While PGEs are the main minerals of interest and extraction at the mine, copper, nickel and gold are also recovered from the operation. The mine is located in a block delineated by two faults in a fairly stable region. Regionally, the geology at the mine is similar and consistent with the rest of the Great Dyke. Locally, the orebody lies at the bottom of the main sequence of sulphide bearing rocks and is about 1.2m above a footwall fault (FWF) that occurs consistently throughout the mining environment. The fault infill material is known to negatively affect the metallurgical process through which the ore is taken to recover PGEs. Due to the clayey nature of its infill material, the fault presents a high risk on regional support (pillars) especially where it coincides with the footwall of mining excavations and can be subjected to water flows.