EXPLOSION GENERATED FRACTURES IN ROCK AND ROCK-LIKE MATERIALS

A novel fracture plane control technique has been developed by simulating stress concentrations due to a pressurized circular cavity with two diametral notches by a series of contiguous cavities. A practical adaptation of this approach consists of one large diameter central hole flanked by two small diameter satellite holes to generate an 'equivalent' notched-hole. Fracture tests with calibrated detonators containing PETN explosive charge in plate samples of granite, Plexiglas, a gypsum cement and a high strength inorganic polymer have yielded highly reproducible and co-linear cracks, even in the presence of pre-existing cracks. Besides providing a reliable method of generating high velocity controlled fractures, the technique may prove to be superior to existing and proposed wall-control blasting methods. © 1990.