Pre-Split blasting is a method of blasting in which a planar crack is propagated by a small, initial blast to better control the final shape of a rock face after a larger, main (production) blast. The crack helps to screen the surroundings from ground vibrations during the firing of the main round.

Specialized pre-split blasting explosives are used. The pre-split holes are blasted prior to the production blast. A minimum time scatter can also be used. Pre-splitting is a very effective method of controlling the final appearance of steep slopes; it can result in a clean sheared face and in some cases it is required. Clean and steep bench faces can increase the overall size and limits of the pit.

Figure: The red row of pre-splitting holes results in a clean free face.