Establishing a UG2 Pillar Strength Formula in South African Platinum Mines

Abstract

In this study, the peak strength of chromitite pillars in South African platinum mines is re-examined by comparing laboratory tests to the Upper Group 2 (UG2) PlatMine pillar strength formula and underground measurements. The laboratory results were stronger than the underground measurements and the strength predicted by the PlatMine formula. The rock mass strength in the PlatMine formula (‘k-value’) was about 70% of the laboratory tests performed on a 50 mm diameter sample. This finding agrees with other researchers who have compared the rock mass strength to laboratory-determined uniaxial compressive strengths. The laboratory tests, underground measurements, and the PlatMine formula all show that the pillars are significantly stronger than traditionally accepted. This finding can help the UG2 mining industry to improve extraction ratios significantly by adopting the PlatMine formula, particularly at deeper levels where bord-and-pillar workings are used. The results presented in this paper will achieve significant revenue creation in the mine where the underground measurements were made.