Numerical analysis for assessing the effects of crown pillar thickness on ore dilution around the sub-level open stopes

Abstract

Sub-level open stopes with delayed backfill are being used to extract massive, tabular, and steeply dipping ore bodies for increased productivity. Crown pillars in the orebody divide mining zones to increase productivity by enabling simultaneous production in two or more zones. Despite their effectiveness, these mining techniques may be accompanied by substantial amounts of overbreak, resulting in considerable ore dilution. This study investigates the effects of crown pillar thickness under various geo-mining conditions on hanging wall overbreak. Under plane strain conditions, 240 non-linear finite element models with the Mohr-Coulomb elastoplastic failure criteria were used for numerical analysis. The outcomes are analyzed in terms of Equivalent Linear Relaxation Depth (ELRD) and Equivalent Linear Overbreak Sloughage (ELOS). The results show that by increasing the crown pillar thickness from 5 m to 8 m, the ELRD and ELOS are reduced by roughly 45 % and 74 %, respectively, for a given material property.