Assessing Pillar Design Strategies in Hard Rock Room-and-Pillar Mining: A Review and Case Studies from the Great Dyke of Zimbabwe

Mining methods, such as room-and-pillar, require that pillars be left to act as primary support, thus maintaining stability as mining proceeds. Leaving these pillars to support the hanging wall results in permanent or temporary sterilisation of valuable mining ore reserves. An economic design of these support pillars requires that the proven and developed ore left to constitute the pillars is minimised. This must be achieved without compromising the essential requirements of guaranteeing the overall stability of the mine. This paper reviews the current developments in underground hard rock pillar design. Mines in Zimbabwe are used as case studies to emphasise the challenges encountered during pillar design and operation. A review of the literature on pillar stress and strength calculation, numerical modelling in pillar design, factors influencing pillar stability, barrier pillars, and machine learning approaches in pillar design is presented. These reviews are then accompanied by summarising the most recent recommendations given by various authors concerning pillar design. The main objective of the exercise is to provide more appropriate insights on the shortfalls of currently used methods and suggest avenues for future research. The authors compiled the recent advances in the subject to assist design engineers and researchers to narrow their focus when designing pillars.