A New Approach for Drilling Method Selection in Open Pit Mines Using Rock Mass Drillability Index

Abstract

Drilling operations play a pivotal role in open-pit mining, where drilling costs represent a significant portion of overall production expenses. Therefore, selecting an optimal drilling system is essential to enhance operational efficiency and cost-effectiveness. In this study, the rock mass drillability index (RDi) classification is employed to introduce a systematic approach for selecting the most appropriate drilling method. The proposed methodology adopts a stepwise framework that integrates mineralogical, mechanical, and physical properties of intact rock, along with the structural characteristics of the rock mass. By combining the cumulative scores of these parameters with the blasthole diameter, a comprehensive decision-making chart divided into eight distinct zones is developed. Each zone corresponds to the most suitable drilling technique among four alternatives: percussive, rotary, percussive-rotary, and down-the-hole (DTH) drilling. Results show that the proposed method successfully recommends the percussive drilling system for rocks characterized by high hardness (Mohs hardness of 6–7) and high uniaxial compressive strength (100–200 MPa). The practicality and effectiveness of the proposed approach are validated through its application to the Komshecheh barite mine in Iran, where the method successfully recommends the most efficient drilling options for site-specific geological conditions.