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A <br /> Review of Blasting Operations at Robinson Brick Company's Siloam Clay Mine <br /> 2.1.1 Review of Blasting Vibration Phenomena: <br /> When explosive charges detonate in rock, nearly all of the available energy is used in breaking and <br /> displacing the rockmass. However, a small portion of the energy is released in the form of <br /> vibration waves, which radiate away from blast charges. When these elastic strain-waves pass <br /> through rock or earth, they cause an oscillating motion in the ground particles. <br /> Abbreviations: <br /> SH = Shear wave, horizontal <br /> SV = Shear wave. vertical <br /> R = Rayleigh wave <br /> P = Compressional wave <br /> eat <br /> Vye�e SH d <br /> � • SSW <br /> Shotfiring Ri,�' <br /> i"- <br /> point r •.. <br /> Figure 2.1—Vibration Waves <br /> Seismic waves decay with distance as they travel through the surrounding area. These waves have <br /> different forms, such as body and surface waves. Their characteristics will vary somewhat with <br /> changes in local geology but the rate at which they die out is reasonably consistent, and allows <br /> regulatory agencies to control blasting operations by means of relationships between distance and <br /> the explosive charge quantities. Each time the distance is doubled, the vibration intensity drops to <br /> about 1/3 of its former value. The consistency of ground motion attenuation is supported by <br /> research done by U.S. Bureau of Mines (Nichols et al., 1979). The researchers found that under <br /> widely varying conditions, if a scaled distance of 50-ft/Ib"' is used to limit charge weights, it is <br /> highly unlikely that ground motion would cause any damage. For the purposes of ground <br /> vibration assessments, scaled distance (SD) is distance from the blast divided by the square root of <br /> GEOTEK& Associates, Inc. Page 4 January 99 <br />