A method of smooth wall rock blasting is provided in which an alignment of boreholes for explosive charging is drilled into rock and a single, smaller diameter empty borehole is drilled close and parallel to, and on each side of each charged borehole. Upon detonation of the charged boreholes, the rock...http://www.google.fr/patents/US4690058?utm_source=gb-gplus-shareBrevet US4690058 - Smooth wall blasting in rock
