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Review of Blasting Operations of Summit Brick <br />ANALYSES of BLASTING IMPACTS, cont' <br />In an earlier USBM study (Bulletin 656, Nichols et al., ]971), it was concluded that if at <br />least 8 milliseconds of delay time separates charges, their effect on ground motion is not <br />cumulative. The "8-millisecond rule" remains an industry and regulatory standard for <br />defining "separate" delays. <br />Blasting researchers, over many years, have developed and verified the validity of using <br />scaled relationships to predict vibration intensity at various distances. These relationships <br />use scaling theory to define the relationship between ground ~ribration particle velocity, <br />charge weight, and distance. Distance is scaled by the square root of charge weight to <br />create a single dependent variable called scaled distance (SD). Various forms of this <br />relationship aze shown in Equation 2-A. <br />ppv = K (SD)rn & SD = Dl W (Equation 2-A) <br />Where: ppv =Peak Particle Velocity fiNsec) <br />K and m =site attenuation constants <br />SD =Scaled Distance Ittnb"21 <br />D =Distance (tt) <br />W =Maximum charge weight per delay Ills.) <br />When plotted on log-log paper, data points defined by scaled distance and measured <br />particle velocity generally fall between boundaries defined by Oriard (1972), as shown in <br />Figure 2.3. The slope of plotted data (in) is usually around -1.6 and the K factor for <br />predicting particle velocity in the upper limit of the normally confined charges 242. For <br />cautious predictions, AG has used a K factor of 300 in aft calculations for estimating <br />particle velocities in the various analyses done in this report. <br />14 <br />