The importance of limiting over break and damage to rock walls at the perimeter of rock excavations can not be underestimated; 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 that justify the effort and expense. ability to maintain safe conditions permitting quicker progress.
Of these perimeter control techniques, pre-split blasting has become the most widely used method.