Excavation of rock at the surface of the ground becomes necessary for several reasons. Drill and blast is the most commonly adopted method for such excavations. In essence, this consists of drilling an array of holes in the rock mass, filling them with explosives and then initiating an explosion so that the release of enormous energy breaks the large rock mass into small pieces. This may appear quite simple, but the techniques of drilling the holes and blasting them have advanced very greatly through the experience gained in the past four centuries over which this excavation method has been used.