Technical study of blasting geometry to reduce the level of fragmentation at the Air Laya mine site pt. Bukit Asam, Tbk.

Abstract Research was conducted at the PT. Bukit Asam Air Laya Mine Site. The aim of the blasting activity is to explode the B2-C interburden layer in order to obtain Seam C coal. The drilling pattern used is a staggered pattern with a vertical drilling direction. The actual blasting geometry used is with a burden of 7 m, spacing of 8 m, hole depth of 8 m, stemming of 4 m, and powder column of 4 m. The level of blasting fragmentation for sizes greater than 160 cm based on theoretical calculations is 26.49 %, while the target set by the company for boulder fragmentation is no more than 20%. To reduce the level of fragmentation, changes were made to the actual geometry by conducting studies using the RL Ash, CJ Konya, and ICI Explosive theories. From this study, recommendations for the proposed blasting geometry were obtained with a burden of 6 m, spacing of 9 m, hole depth of 11.66 m, stemming of 5.14 m, and powder column of 6.52 m. With these changes in geometry, fragmentation measuring more than 160 cm was obtained at 17.15%, or it can be said to achieve the fragmentation target of less than 20%.