Method of breaking a full face of rock for constructing shafts and tunnels

摘要

A method for breaking a longer round more efficiently in a full face of rock, to construct shafts or tunnels. In the method a relief hole having at least a 200 mm diameter and at least a 15 to 18 foot depth is drilled. Primary and secondary blast holes are drilled about the relief hole, approximately axially parallel to the relief hole. Most of the blast holes are drilled simultaneously with the relief hole. The relief hole is drilled by an in-the-hole (ITH) hammer drill, which if necessary is removed after drilling the relief hole, to allow blast holes to be drilled immediately adjacent the relief hole. The relief hole is drilled at least 10 to 15 percent deeper than the blast holes. Explosive charges are then inserted into the relief hole and most of the blast holes and are detonated in sequence.