An approach for unplanned dilution assessment in open stope with consideration of the stope shape irregularity

This study aims to propose an assessment tool for unplanned dilution, considering the irregularity of the stope shapes due to the overbreak and underbreak of the stope walls. Data from the Ridder-Sokolny mine, an underground mine, located in East Kazakhstan, was used for the study. On the basis of the collected dilution data, the stopes were categorized into three types depending on the extent of the irregularity: simple, semi-complex, and complex shape. Numerical modelling was performed to illustrate the effect of the stope shape complexity on the overall instability, while the Rock Engineering System (RES) was employed to introduce a Dilution Index (DI) with the purpose of quantifying the stope shape irregularity effect. The results suggested that instabilities and rock failure are likely to occur with an increase in the stope shape complexity as tension increases while the strength factor decreases. Furthermore, the stope shape irregularity had the most significant effect on the DI system compared to other parameters affecting the dilution. The results indicated that the DI is a very good predictor of unplanned dilution and a fairly good predictor of stope loss, which indicates advantages over the conventional dilution graph method. It is concluded that the DI could be an alternative for unplanned stope dilution estimations depending on the stope shape complexity.