Abstract
ABSTRACT: Unplanned dilution due to stope overbreak and sloughing can impose significant economic burdens on mines employing open stoping methods, particularly when stope designs are not optimized. Empirical dilution graph methods are commonly applied due to their practicality; however, they may lead to excessive dilution because of their inability to account for site-specific geological conditions and other local factors. This study proposes a dimensionless index, the Overbreak Index (O-index), that effectively relates unplanned dilution to its controlling parameters, providing a quantitative measure of stope susceptibility to dilution. The input parameters for the O-index system include stope geometry, geomechanical characteristics, and geoengineering-related parameters. The interactions among influencing factors were evaluated using the Rock Engineering Systems (RES) framework. An unplanned dilution dataset from a mining operation was compiled and used to establish the proposed index. Overall, the validation demonstrated strong agreement between the proposed O-index and actual dilution, with a correlation coefficient of R = 0.83, outperforming the empirical ELOS graph method. The study concludes that the O-index offers a reliable tool for quantifying dilution in open stoping operations and can effectively complement the widely used ELOS graph approach.