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~-- o 0 <br />-' THE PREVENTION OF DAMAGE TC) PROPERTY <br /> Without question, the most common single cause of damage to <br /> property resulting from blasting operations is due to flyrock. <br /> Obviously, the regulations~to protect the citizen frcun injury will <br /> also protect his property from damage, and should damage occur from <br /> flyrock, it is also evidence of a violation of the regulations. The <br /> evidence is also virtually indisputable, except, as noted on Page <br /> 31, in the case of windshield glass breakage, or hail damage to <br />~, <br />~( <br />J vehicles. <br />I,-,_ While ground motion, or vibration, is the second most cotmimn <br /> cause of damage, it is nevertheless only truthful to point out that <br /> actual damage due to blast vibrations is in fact quite rare. This <br /> is mentioned as much to stress the very careful and conservative <br /> nature of the OSI~tE regulations on vibration limitations, than to <br /> defend the mine operator. <br /> These limitations, shown on pages 22-25 of this manual, allow <br /> under some circumstances up to 2.0 inches par second particle <br /> velocity, and under others as low as 0.2 inches par second, because <br /> of the different damage effects of ground motion of varying <br /> frequencies. This also explains the apparent anomaly of permitting <br /> higher velocities at short distances, because the frequencies of <br />f~' 111 <br />