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

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 using statistical 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. Keywords: Drilling, Blasting, Fragmentation, Kuz-Ram Model, Wipfrag Softwar