The Influence of Blast Hole Geometry on Limestone Fragmentation in Central Buton Regency

Abstract

This study aims to analyze the effect of blast hole geometry on limestone fragmentation during blasting activities at PT Diamond Alfa Propertindo, Central Buton Regency, Southeast Sulawesi. The geometric parameters analyzed include burden, spacing, hole depth, fill column length, and stemming, while fragmentation quality is evaluated based on the average fragmentation size, P20, P50, P80 values, and top size using Split Desktop software. The study was conducted on five blasting activities with an evaluative quantitative approach through direct measurements in the field and analysis of digital images of the blasting results. The results showed that burden and spacing in all blasting activities were relatively constant at 3 m, while the main variations were found in hole depth, fill column length, and stemming. The average fragmentation size decreased from 0.64 m in the first blasting to 0.18 m in the fifth blasting. The Split Desktop results also showed a decrease in the P80 value from 647.04 mm to 184.59 mm, and a decrease in the top size from 800.30 mm to 313.51 mm. These findings indicate that changes in blasthole geometry, particularly hole depth, fill column length, and stemming, significantly impact the size distribution of limestone fragmentation. The fourth blasting session produced an average fragmentation of 0.39 m, still within the operational target range of 0.3–0.6 m, thus being considered the most proportional design to support efficient loading, transport, and material processing. This study confirms that controlling blasthole geometry is a critical factor in optimizing limestone blasting and increasing mine production efficiency.