CONTROLLED FRACTURE TECHNIQUES FOR CONTINUOUS D DRILL AND BLAST

THE COMMERCIAL APPLICATION OF SMALL CHARGE, CONTINUOUS DRILLAND BLAST AND SYSTEMS HAS NOT BEEN REALIZED PRIMARILY BECAUSE OF THE HAZARDS AND OPERATIONAL PROBLEMS DERIVING FROM THE (ALBEIT SMALLER) EXPLOSIVE CHARGES EMPLOYED. CONSIDERABLE RECENT WORK ON ROCK FRAGMENTATION BY CONTROLLEDFRACTURE BLASTING CONDUCTED AT THE UNIVERSITY OF MARYLAND AND ELSEWHERE HAS REVEALED THAT WITH AN APPROPRIATE SHOTHOLEGEOMETRY AND PLACEMENT OF CHARGES THEREIN, THE QUANTITY OF EXPLOSIVE REQUIRED TO FRACTURE AND FRAGMENT ROCK CAN BE SIGNIFICANTLY REDUCED. IT HAS BEEN SHOWN THAT PRESPLITTING CAN INCREASE THE FRAGMENTATION REALIZED WITH SMALLER CHARGES. OTHER WORK ON DYNAMIC BUT NON-EXPLOSIVE ROCK EXCAVATION TECHNIQUES HAS SHOWN THAT VERY EFFICIENT ROCK BREAKAGE CAN BE REALIZED WITH RAPIDLY PRESSURIZED SHALLOW BOREHOLES. IT IS PROPOSED TO CONDUCT NUMEROUS SINGLE AND MULTI HOLE EXPLOSIVE TESTS IN BOTH PHOTOELASTIC MATERIAL AND ROCK SO AS TO ESTABLISH THE TECHNIQUES AND POTENTIAL FOR APPLYING CONTROLLED FRACTURE BLASTING TECHNIQUES TO SAMLL CHARGE CONTINUOUS DRILL AND BLAST SYSTEMS. THESE TESTS WILL INCLUDE INSTRUMENTATION AND MEASUREMENTS TO STUDY THE PHENOMENA (SUCH AS FRACTURE PRESSURIZATION) CONTROLLING THE ROCK FRAGMENTATION.