The design and strength of pillars are important parameters when implementing the room-and-pillar mining method in a limestone mine. The process becomes complex with the presence of the karst voids which are frequent phenomena in a carbonate rock formation. This research is a continuation of a previous study aimed at studying the effect of karst void on the strength of a particular limestone pillar. Using the calculated pillar strength and the estimated redistributed stresses, it was assessed that the pillar is capable of countering more stress than is currently imparted on it. Numerical modeling studies combining in situ stress determination and excavation sequencing were used to estimate the existing stresses on the pillar. Different possibilities of modification to existing pillar design were simulated using distinct element method (DEM) modeling to determine a better design. Discrete fracture networks (DFN) were included to imitate the effect of the presence of discontinuities. An effort is made to understand the variation of pillar strength with height for karst-affected pillars using two constitutive models. This study serves as a preliminary investigation for improving the future design of pillars while recovering old pillars prone to karst formation.
Full-text paper:
Mining, Metallurgy & Exploration (2023) 40:529–541, https://doi.org/10.1007/s42461-023-00733-1
