Blasting design for obtaining desired fragmentation

The empirical prediction of expected fragmentation is in most cases carried out by using the Kuz-Ram model. By doing this, the Rosin-Rammler theory is applied. This theory, first proposed by V. M. Kuznetsov (1973), gives a reasonable description of the blasted rock fragmentation. Using this approach, one calculates a rock factor that describes the nature and geology of the rock. The uniformity index is also obtained that characterizes the explosive loading and blast pattern type and dimensions. This allows the characteristic size and size distribution to be calculated according to the Rosin-Rammler procedure. Due to the amount of too many input rock mass parameters, that are not unambiguously determined, the rock factor may also not be satisfactory and this unfavorably influences the fragmentation prediction. The later work of others, particularly that of Lilly (1986) and Cunningham (1983, 1987) was useful for improving the efficiency of that approach. The authors have developed the program "SB" enabling the user to directly influence the blasted material size distribution by selecting a cumulative mass percentage of the required fraction size. By the required selection for the calibrated rock factor, the program computes the required drill hole pattern. The program is used for computing the drilling costs, the costs of machine crushing of larger blocks remaining after blasting and the costs of primary crushing. From the analysis of exploitation and primary processing costs it can be concluded that blasting is the cheapest method of rock fragmentation. The total costs for the required quantity of blasted material are significantly reduced by the use of smaller drill hole patterns. The costs for drilling and explosive do indeed increase in that way, but the costs of loading, transportation, crushing and grinding of the mineral are significantly smaller.