PlatMine pillar strength formula for the UG2 Reef

Abstract

The Upper Group 2 (UG2) chromitite reef is a shallow-dipping stratiform tabular orebody in the South African Bushveld Complex, which strikes for hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 500 m. Pillars are widely used to support the open stopes and bords. Little work has been done in the past to determine the strength of pillars on the UG2 Reef and design was done using formulae developed for other hard-rock mines. This has led to oversized pillars with consequent sterilization of ore. In this paper we describe a back-analysis of stable and failed UG2 pillars on the Bushveld platinum mines, and provides a strength formula for UG2 pillars. The formula may be used cautiously on all Bushveld platinum mines with similar geotechnical, geometrical, and geomechanical conditions to the pillars in the database.

A study of UG2 pillar strength using a new pillar database

“…Work was conducted in the PlatMine research programme to develop local pillar strength formulae for the platinum industry. Watson et al (2008) compiled a database of 179 Merensky Reef pillars, of which 109 were stable. In 2020, developed a new UG2 pillar strength formula for the platinum industry based on a larger data-set of 167 UG2 pillars.…”