Method of drilling a borehole

摘要

To drill a hole (1) through a mineral material (2) incorporating embedded materials (3) of a specifically different nature, e.g. reinforced concrete with embedded reinforcement rods, the hole is drilled by a bit (4) at the drill until it strikes the embedded object. The bit is changed to allow the drilling to proceed through it. When the hole is through the obstruction, the first bit is replaced for further drilling. The tool is a hammer drill, using a rock bit for the first stage. The second bit is a ring bit, to drill through the steel rods.