Laserfiche WebLink
Review of Blasting Operations at Denver Brick Company's Golden Mine <br /> 40 Hz, a safe particle velocity maximum of 51 mm/s (2.0 in/s) is <br /> recommended for all houses." <br /> It should be noted that the USBM RI 8507 recommendations are designed to prevent even <br /> threshold damage in residences of lower-quality construction. Threshold damage was defined <br /> as: <br /> "Threshold damage was defined as the occurrence of cosmetic damage; <br /> that is the most superficial interior cracking of the type that develops in all <br /> homes independent of blasting." <br /> In an earlier USBM study (Bulletin 656, Nichols et al., 1971), it was concluded that if at least 8 <br /> milliseconds of delay time separates charges, their effect on ground motion is not cumulative. <br /> The "8-millisecond rule" remains an industry and regulatory standard for defining "separate" <br /> delays with respect to charge weight per delay.. <br /> Blasting researchers, over many years, have developed and verified the validity of using scaled <br /> relationships to predict vibration intensity at various distances. These relationships use scaling <br /> theory to define the relationship between ground vibration particle velocity, charge weight, and <br /> distance, Distance is scaled by the square root of charge weight to create a single dependent <br /> variable called scaled distance (SD). Various forms of this relationship are shown in Equation <br /> 2.1. <br /> Equation 2.1: <br /> PPV=K D m or PPV=K(D,r <br /> Where: PPV=Peak Particle velocity(in/s) <br /> D=Distance(ft) <br /> W=Maximum Charge-weight-per-delay(lb) <br /> K=Rock Energy Transfer Constant(K-factor) <br /> m=Decay Constant <br /> D.=Scaled Distance(ft-Ib'°S) <br /> When plotted on log-log paper, data points defined by scaled distance and measured particle <br /> velocity generally fall between boundaries defined by Oriard (1972), as shown in Figure 2.3. The <br /> slope of plotted data (m) is usually around - 1.6 and the K factor for predicting particle velocity in <br /> the upper limit of the normally confined charges is 242. For cautious predictions, Stanto Group <br /> Inchas used a K factor of 300 in all calculations for estimating particle velocities in the various <br /> analyses done in this report. <br /> 9 <br />