Bolegenov, Adil2024-07-102024-07-102024-04-18Bolegenov, Adil. (2024). Development Of An Unplanned Overbreak Index For Open Stope Mining: Accounting For Design Uncertainty. Nazarbayev University School of Mining and Geoscienceshttp://nur.nu.edu.kz/handle/123456789/8104Unplanned dilution can pose a huge burden on the profitability of operations in mines exploiting open stoping mining methods if these are not adequately designed. The empirical stability graph methods are commonly used for these purposes due to their practicability. Despite their merits, experience shows that these graphical design methods can also lead to excessive unplanned dilution which is not surprising since the stability graph method is an approximate design method by nature. This is due to many reasons, for example the unavoidable uncertainties (both epistemic and aleatory) that come with design parameters. Therefore, there is an increasing need for more accurate design tools in the mining industry. Motivated by these aspects, the purpose of this research is to revisit the conventional stability graphs method for open stope design and to propose alternative design tools that could address some of the limitations of the conventional methods. To this end, firstly, a database of unplanned dilution cases collected from sublevel open stoping operations was compiled and the performance of the conventional stability graph method was examined. Next, based on the compiled data, a new overbreak index (DI) was proposed using the Rock Engineering Systems methodological framework. In addition, the effect of aleatory uncertainties on the stability graph method was explored through a reliability analysis. This was accomplished by using the First Order Reliability Method (FORM) to determine the probability of occurrence of unplanned overbreak. The overall results indicated that: the stability graph method yielded accuracies ranging from 9-78%, depending on the ELOS levels; the proposed Overbreak Index highly correlated with the actual ELOS values. In addition, the reliability analysis revealed that the probability associated with the unplanned ELOS varied between 15-100% depending on the rock domains and the wall types. It was concluded that the Overbreak Index and the reliability analysis results could be considered additional tools useful for a more reliable open stope design if uncertainties associated with input parameters of the design must be considered.enAttribution-NonCommercial-NoDerivs 3.0 United StatesType of access: EmbargoMaster's thesis