Design of blast pattern with perimeter controls for use in poor ground conditions

This study contains research information on how to counter adverse results (over break, dilution and reduced safety) when conducting blasting operations using Mimosa mine in Zvishavane as a case study. Two perimeter blasting techniques were incorporated into the original blasting pattern used at the mine in order to analyse their effect on blasting operations as compared to the original pattern. To achieve this, a trial blast of each blasting pattern was carried out and the resulting mining heights, dilution and number of bolts replaced to improve safety were recorded and analysed. These results indicated that using perimeter blasting as a method of controlling a blast was capable of minimizing or possibly eliminating some of the negative effects of blasting in poor ground conditions. Further analysis was carried out between the two perimeter blasting techniques and it was concluded that smooth wall blasting was the best method to use in blasting in poor ground conditions. This was as a result of its low drilling times as well as cheaper drilling cost as compared to line drilling.