Influence of air-deck blasting on fragmentation in jointed rocks in an open-pit manganese mine

• Published in: Engineering geology Vol. 57; no. 1; pp. 13 - 29
• Main Authors: Jhanwar, J.C, Jethwa, J.L, Reddy, A.H
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2000; Elsevier
• Subjects: Air-deck; Applied sciences; Blasting; Buildings. Public works; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Engineering geology; Exact sciences and technology; Fragmentation; Geotechnics; Jointed rock; Miscellaneous; Open pit; Soil mechanics. Rocks mechanics; Air-deck; Jointed rock; Open pit; Blasting; Fragmentation; Discontinuity; Geology; Site analysis; Theory; Ore extraction; Blasting operation; Shock wave; Particle size distribution; Open pit mine; Geotechnics; Manganese
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/S0013-7952(99)00125-8

The influence of air-deck blasting on fragmentation in jointed rock masses of a manganese open-pit mine has been investigated. It is revealed that air-deck blasting improves the degree of fragmentation and produces more uniform fragmentation compared with conventional blasting. Mean fragment size (MFS) reduces from a range of 0.36–1.0 m to a range of 0.27–0.51 m. Fragmentation index (FI) and blast-induced fragmentation increase from 1.38 to 4.34 and from 37–65% to 66–100% respectively. Empirical correlations have been developed to estimate MFS and FI from conventional and air-deck blasting on the basis of Bieniawski's rock mass rating, powder factor and ratio of spacing to burden. Results indicate that air-deck blasting could be more effective in very low to low strength moderately jointed rock masses than in medium strength highly jointed rock masses.