Blasting operations play a pivotal role in the overall economics of opencast mines. The blasting subsystem affects all the other associated subsystems, ie loading, transport, crushing and milling operations. Fragmentation control through effective blast design and its effect on productivity is a challenging job for the practicing blasting engineer due to inadequate knowledge of actual explosive energy released in the borehole, effect of varying initiation practice in blast design and its effect on explosive energy release characteristic. This paper describes the result of a systematic study on the impact of blast design parameters on rock fragmentation at two mines in India. Both the mines use draglines and shovel-dumper combination for removal of overburden. Despite its pivotal role in controlling the overall economics of a mining operation, the expected blasting performance is often judged almost exclusively on the basis of poorly defined parameters such as powder factor and is often qualitative, which results in a very subjective assessment of blasting performance. Such an approach is a very poor substitute for accurate assessment of explosive and blasting performance. Forty-seven blasts were conducted with varying blast designs and charging patterns and their impact on the rock fragmentation are documented. A high-speed camera was deployed to record the detonation sequences of the blasts. The efficiency of the loading machines was also correlated with the mean fragment size obtained from the fragmentation analyses.CITATION:Singh, P K, Roy, M P, Drebenstedt, C and Prasad, B, 2015. Blast design parameters and their impact on rock fragmentation, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 755-762 (The Australasian Institute of Mining and Metallurgy: Melbourne).