PULSED WATER JETS, GENERATED BY CUMULATIVE NOZZLE DEVICES, HAVE A PRESSURE-TIME BEHAVIOR WHICH CAN CAUSE ROCK TO FAIL BY THREE DISTINCT MODES: MECHANICAL CRUSHING, HYDRAULIC EROSION AND LARGE-SCALE PROPAGATION OF FLUID PRESSURIZED CRACKS.

PULSED WATER JETS, GENERATED BY CUMULATIVE NOZZLE DEVICES, HAVE A PRESSURE-TIME BEHAVIOR WHICH CAN CAUSE ROCK TO FAIL BY THREE DISTINCT MODES: MECHANICAL CRUSHING, HYDRAULIC EROSION AND LARGE-SCALE PROPAGATION OF FLUID PRESSURIZED CRACKS. THE INTERACTIONS BETWEEN THESE THREE MODES OF FAILURE CAN BE EXPLOITED SO AS TO YIELD ROCK EXCAVATION AT AT SPECIFIC ENERGIES COMPARABLE TO THOSE FOR CONVENTIONAL DRILL AND BLAST. PULSED JETS HAVE BEEN MOST LIMITED IN IN THEIR ABILITY TO PROVIDE A SUSTAINED PRESSURE FOR THE THE PROPAGATION OF LARGE-SCALE FRACTURES AND IN THE LACK OF A MEANS FOR GENERATING THE JETS AT HIGH REPETITION RATES. TWO NEW CONCEPTS NOW PROVIDE A MEANS FOR OVERCOMING THESE LIMITATIONS. BY COMBINING EXISTING PULSED-JET TECHNOLOGIES WITH A PROPELLANT DRIVEN CONTINUOUS JET GENERATION CAPABILITY, THE REQUIRED LATE-TIME PRESSURE BEHAVIOR CAN BE OBTAINED. BY MEANS OF THE OSCILLATORY MOTION OF THE ENTIRE JET GENERATING DEVICE, THE NOZZLE MAY BE EMPTIED AND THE JET GENERATING PISTON POSITIONED THUS ALLOWING FOR RAPID CYCLIC OPERATION. IT IS PROPOSED TO CONDUCT EXPERIMENTS WITH A DEVICE INCORPORATING THE BASIC FEATURES REQUIRED FOR COMBINED-JET GENERATION AND RAPID CYCLIC OPERATION, SO AS TO ESTABLISH THE APPLICABILITY OF THESE NEW CONCEPTS TO RAPID ROCK EXCAVATION.