CONTROLLED FRACTURE METHOD AND APPARATUS FOR BREAKING HARD COMPACT ROCK AND CONCRETE MATERIALS

摘要

Hard compact materials, such as rock, concrete, et cetera, are broken byigniting an appropriately designed explosive orpropellant charge (101) carried in a special charge-containing device (27)with a short barrel (25) which is inserted and sealed intoa pre-drilled hole (9) of particular geometry. Holes (9) are percussivelydrilled with microfractures (19) in and around hole bot-toms (13) to provide fracture initiation sites at the hole bottom (13) so asto provide preferred fracture initiation roughly parallelto a free surface of material being excavated. The propellant charge (101) maybe placed and ignited within a charge-containingdevice (27) which includes a short barrel (25) inserted into the holes (9)drilled into the material to be broken. The barrel (25) ofthis device (27) may be further sealed into the holes (9) by a helical shim(21) or by having a slight shoulder (53) on the barrelpressed against a slight step (49) on the hole wall (43).