The U.S. Bureau of Mines has patented an abrasive-enhanced waterjet rock drill. Drilling occurs through the action of a 10,000-psi, 20- gpm waterjet containing 20 lb/min of entrained abrasives. This 10,000-psi drill has drilled hard rock with an unconfined compressive strength of 73,000 psi. In addition to drilling holes in hard rock and reinforced concrete, this drill can cut deep, narrow kerfs in dimension stone, drill through rubble, and chamber holes.
Proc. Conf. on Shaft Drilling Tech., Las Vegas; 4-91, Inst. Shaft Drilling Technol, 1991, 12 Pp