Drilling plays a decisive role in blasting performance by directly influencing rock fragmentation, muckpile profile, and the energy efficiency of explosives.
Key parameters include hole diameter, spacing (distance between holes in a row), burden (distance to the free face), and hole depth with subdrilling. According to Régis Kambire (2023), using a larger hole diameter reduces drilling costs and improves detonation velocity for better fragmentation, but it can lead to less uniform energy distribution if the rock mass is highly fractured.
- Typical spacing:25 times the burden for uniform fragmentation
- Burden: approximately 40 times the hole diameter in mm (e.g., 4 m for 100 mm holes)
- Depth: adjusted to bench height plus subdrilling (0.15–0.35 times the diameter) to avoid toe formation
Precise blast geometry (blast pattern = burden × spacing) optimizes explosive energy distribution, reducing oversize boulders and improving downstream loading efficiency. Inclined holes (10–30°) minimize overhangs, improve toe breakage, and reduce vibrations compared to vertical holes. Drill hole deviations (>3%) or irregular bench faces cause excessive flyrock and uneven fragmentation.
Drilling quality depends on rock mass characteristics (fracturing, density) and equipment performance; accurate drilling reduces explosive consumption and secondary costs such as secondary breakage. In open-pit mining, these parameters are adjusted using empirical formulas such as the Langefors equation to predict the theoretical burden.
