Drill and Blast Performance Evaluation at the Obra Pit of Chirano Gold Mines Ltd, Ghana


  • Peter Arroja Eshun University of Mines and Technology
  • B. O. Afum UMaT
  • Abigail Baffour Karikari


This paper investigates the causes of inefficient fragmentation and formation of toes in the Obra pit of Chirano Gold Mines Ltd and recommends best practices in order to produce optimum fragmentation to feed the crusher at a reduced cost and to provide good working pit floors. The methods employed included: drilling performance analysis usingstatistical methods; fragmentation analysis of blasting performance using Kuz-Ram Model and Wipfrag software; determination of the velocity of detonation of the bulk explosive using MREL Micro Trap VOD/Data Recorder; and estimation of the cost of secondary drilling and blasting using Mine Management Reporting Software. From the analyses, it was observed that the blast designed parameters and blasting practices were acceptable to produce good fragmentation but the actual drilling parameters deviated from the designed parameters by about 25%, 24% and 26% in hole depth, burden and spacing respectively. It was concluded that the cause of the ineffective fragmentation leading to high cost of secondary breakage and uneven pit floors was due to operational errors during drilling. It is therefore recommended that in order to reduce excessive deviations in the drilling parameters, periodic training of operators must be conducted,supervision of drilling and blasting operations must be enhanced, and inclinometers should be used during drilling activities to ensure the accuracy and precision of all blast holes.


Afum B. O. and Temeng V. A. (2015), “Reducing Drill and Blast Cost through Blast Optimisation – A Case Studyâ€, Ghana Mining Journal, Vol. 15, No. 2, pp. 50 - 57.

Anon., 2010, “Digital Imaging System for Process Analysisâ€, Split-Online Brochure, http://www. spliteng.com/dloads/. Accessed: 7 July 2015, 2 pp.

Cunningham, C. V. B. (1983), “The Kuz-Ram Model for Prediction of Fragmentation from Blastingâ€, Proceedings of 1st International Symposium on Rock Fragmentation by Blasting, Lulea, pp. 439-454.

Elevli, B. and Arpaz, E. (2010), “Evaluation of Parameters affected on the Blast Induced Ground Vibration (BIGV) by using Relation Diagram Method (RDM)â€, Acta Montanistica Slovaca, Vol. 15, No. 4, pp. 261 – 268.

Hirdes, W., Senger, R., Adjei, E., Afa, E., Loh, G., and Tettey, A. (1993), “Geological Map of Southwest Ghana 1:100 000; Sheets Wiawso (0603D), Asafo (0603C), Kukuom (0603B), Goaso (0603A), Sunyani (0703D) and Berekum (0703C); Ghanaian-German Mineral Prospecting Projectâ€, Technical Cooperation Project No. 80; 6 maps, 24x17cm.

Jimeno, C. L., Jimeno E. L. and Carcedo F. J. A (1995), Drilling and Blasting of Rocks, Balkema, Rotterdam, pp. 183 - 200.

Kenworthy, S., Noormohamed, K., Stuart H., and Hodkiewicz, P., (2009), “Mapping and Three-Dimensional Modelling of Structural Controls in the Chirano Gold Deposits, Ghana - Keys to Better near-Mine Exploration Targetingâ€, Seventh International Mining Geology Conference, pp. 101- 106.

Kose, H., Aksoy, C. O., Gönen, A., Kun, M. and Malli, T. (2005), “Economic Evaluation of Optimum Bench Height in Quarriesâ€, The Journal of the South African Institute of Mining and Metallurgy, pp. 125 - 135.

Maerz, N. H. and Palangio, T. C. (1999), “WipFrag System II - Online Fragmentation Analysisâ€, FRAGBLAST 6, Sixth International Symposium for Rock Fragmentation by Blasting, Johannesburg, South Africa, Aug. 8-12, 1999, pp. 111-115.

Maerz, N. H. and Zhou, W. (1998), “Optical Digital Fragmentation Measuring Systems - Inherent Sources of Errorâ€, FRAGBLAST, The International Journal for Blasting and Fragmentationâ€, Vol. 2, No. 4, pp. 415-431.

Maerz, N. H. and Zhou, W. (2000), Calibration of Optical Digital Fragmentation Measuring Systems, FRAGBLAST, The International Journal For Blasting and Fragmentation, Vol. 4, No.2, pp. 126-138.

Olofsson, S. O. (1990), Applied Explosives Technology for Construction and Mining, Applex Publishers, Sweden, pp. 62 - 83.

Schleifer, J. and Tessier, B. (2001) “Fragmentation Assessment using the Fragscan System: Quality of a Blastâ€, Explosives in Mining Conference, Explo 2001, Hunter Valley, NSW, Australia, October 2001, AusIMM, pp. 365-372.

Siddiqui, F. I., Shah, S. M. A. and Behan, M. Y. (2009), “Measurement of Size Distribution of Blasted Rock Using Digital Image Processingâ€, JKAU: Eng. Sci., Vol. 20, No. 2, pp. 81 – 93.

Singh, D. P., and Sastry, I. R. (1987), “An Investigation into the Effect of Blast Geometry On Rock Fragmentationâ€, 6th ISRM Congress, Banaras Hindu University, August 30 - September 3, 1987, Montreal, Canada, unpaginated.

Stuart, H., (2009), “Chirano Gold Project, Republic of Ghanaâ€, Technical Report, Red Back Mining Inc., 140 pp.

Whiteaker, R., (2008), “Obra Deposit and Regional Mapping of Parts of the Chirano Concession, Western Ghanaâ€, Technical Report, Red Back Mining Inc., p. 6.