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Blasting Impacts and Rode Slope Stability Assessment far Cottonwood Quarry in Grand Cotmty, Co <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 <br />changes. Vibration frequency is a measure of how many oscillations a ground particle makes per <br />second of time. Frequency is reported in units of Hertz (Hz), which is equivalent to cycles per <br />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 <br />in/s) can be detected by the human body when background noise and vibration levels are low. A <br />curve plotting intensities of ground motion and motion frequencies that will not cause cosmetic <br />cracking in drywall and piaster -lath walls are shown in Figure 3.3. Vibration intensity is <br />expressed as Peak Particle Velocity (PPV), which is simply the maximum speed that the ground <br />moves while it temporarily shakes. Since ground -shaking speeds are very small, it is measured in <br />inches per second (in/s). Frequency of motion or cycles per second is a measure of how many <br />times a particle of ground moves back and forth (or up and down) in one second of time. <br />Frequency is expressed in units of Hertz (W). <br />The "safe limits" published by the US Bureau of Mines (USBM) in Report of Investigations (RI) <br />8507, are specifically intended to protect typical wood flame homes. Significantly higher PPV <br />limits, ranging from 5.0 to 20 in/s, are used to protect buried pipes and other heavy civil <br />USBM fZR 8507 "Sab Leven" Qlve <br />19.0 nmfs <br />(0.75 M) <br />12%!lila'$ <br />12 <br />WBnTds <br />tZOWO <br />a <br />6 a 10 m 30 40 so a0 100 <br />FREQUENCY, Hz <br />Figure 3.3 -- USBM "Safe Lever' vibration curve from RI 8507 <br />REVEY Associates, Inc. Page 6 April 2004 <br />264 (10) <br />203(s) <br />y <br />132 (e) <br />C <br />102 (4) <br />50.8 42) <br />r� <br />1-- <br />PPV p <br />25 4 (1) <br />� <br />Uj <br />tj <br />—j <br />10.2(4) <br />U <br />a <br />USBM fZR 8507 "Sab Leven" Qlve <br />19.0 nmfs <br />(0.75 M) <br />12%!lila'$ <br />12 <br />WBnTds <br />tZOWO <br />a <br />6 a 10 m 30 40 so a0 100 <br />FREQUENCY, Hz <br />Figure 3.3 -- USBM "Safe Lever' vibration curve from RI 8507 <br />REVEY Associates, Inc. Page 6 April 2004 <br />