The importance of limiting over break and damage to rock walls at the perimeter of rock excavations can not be under estimated. To minimize these undesirable effects there are several perimeter blasting techniques which are available. Over past years these controlled blasting methods have undergone a great deal of improvement and are now common in open pit mining as well as in public works projects. These techniques are namely smooth wall blasting (or trim blasting), line drilling, cushion blasting, pre-split blasting, fracture control method, and linear shaped charge method. Although more costly to implement, these methods offer the following beneficial qualities which justify the effort and expense. ability to maintain safe conditions permitting quicker progress.
- increased stability of the rock wall
- improved stripping ratios
- applied to ore limits it can reduce dilution
- less broken rock to load and transport
Of these perimeter control techniques, pre-split blasting has become the most widely used method.
This method will be reviewed in full covering the relevant background theory including a review of factors which affect pre-split blasting results, the practical aspects and considerations, and the benefits to be gained by using this method.