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Blast-produced Fractures in Lithonia Granite.
NTIS: PB 234 071 :38 pages
The Bureau of Mines has studied the fracturing produced in the vicinity of large-diameter blastholes in Lithonia granite. Cores were taken from the vicinity of AN-FO production blasts and examined using a total of seven laboratory and field measurement techniques to delineate zones of damage and to evaluate the effectiveness of the seven diagnostic tests for fracture-state determination laboratory measurements of acoustic pulse velocity, porosity, permeability, compressive strength, and young's modulus indicated the extent of fracturing, with the acoustic techniques providing the best means of distinguishing between fractured and unfractured core. A severely fractured zone was found to extend approximately 25 inches (64 cm) from the center of the 6 1/2-inch blastholes, equivalent to 8 blasthole radii. A second zone, characterized by a lesser degree of fracturing, extended from 25 to 45 inches (64 to 114 cm) or 8- to 14-blasthole radii. Beyond 45 inches (114 cm) the rock was undamaged.
IH; Report of Investigations
NTIS Accession No.
NTIS: PB 234 071
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division