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Janice Lynn Bennett - 81422.PDF Page 10 <br />Blasting Impacts Assessment for the Proposed GCC Rio Grande, Inc. Quarry in Pueblo County, Colorado <br />• Particle velocity <br />. Particle acceleration <br />• Vibration frequency <br />Displacement is a measure of ground particle travel distance or location with respect to time. <br />Particle velocity measures the speed of movement and acceleration is the rate of velocity changes. <br />Vibration frequency is a measure of how many oscillations a ground particle makes per second of <br />time. Frequency is reported in units of Hertz (Hz), which is equivalent to cycles per second. <br />3.2 Vibration Perception and Damage Criteria <br />The average person is quite sensitive to ground motion, and levels as low as 0.50 mm /s (0.02 in /s) <br />can be detected by the human body when background noise and vibration levels are low. A curve <br />plotting intensities of ground motion and motion frequencies that will not cause cosmetic cracking <br />in drywall and plaster -lath walls are shown in Figure 3.3. Vibration intensity is expressed as Peak <br />Particle Velocity (PPV), which is simply the maximum speed that the ground moves while it <br />temporarily shakes. Since ground- shaking speeds are very small, it measured in inches per second <br />(in /s). Frequency units are hertz (Hz) or cycles per second, which is a measure of how many times <br />a particle of ground shook back and forth is one second. These limits "safe limits" published by <br />the US Bureau of Mines (USBM) in Report of Investigations (RI) 8507, are intended only to <br />protect typical wood frame homes. Significantly higher PPV limits, ranging from 5.0 to 20 in /s, <br />are used to protect buried pipes and other heavy civil structures. <br />251 (I0) <br />- 203 (8) <br />Fi <br />▪ 152 (6) <br />gu <br />re - 102 (4) <br />3. <br />3_ 1- <br />� 50.8 <br />U _ <br />U PP 254 9) <br />SB 20.3 (8) <br />15 2 (.6) <br />M <br />"S fl 102(4) <br />afe <br />Le Q 5.1 (.2) <br />vel <br />2 5 (.1) <br />vi <br />1 REVEY Associates, Inc <br />USBM RI 8507 "Safe Level" Curve <br />1 <br />2 <br />19.0 mm /s <br />(0 75 in /s) <br />pyvell <br />Raster &Lath • <br />12.7 mm <br />(0 50 m/s) <br />Page 7 <br />1 1 <br />6 8 10 <br />;12 <br />FREQUENCY, Hz <br />20 <br />30 40 <br />50 8 17rr15 <br />(20 Int) <br />40 <br />I I <br />60 80 100 <br />July 2002 <br />