Laserfiche WebLink
Blasting Impacts and Rock Slope Stability Assessment for Cottonwood Quarry in GraM County,CO <br /> 10 *^r~r-t 130 <br /> n <br /> -10 F <br /> no <br /> _� C A <br /> -70 <br /> 10 100 =0 loaoo w <br /> Freywey(MR) 10 <br /> Weighting Scaks <br /> 120 s•oc i,c+ayn� <br /> ,fa <br /> 1+v. foo <br /> 90 <br /> A•`"s+f6t'^! 110 Sae 7.A-Sowt,.N <br /> 0 1 l0D <br /> iam <br /> TW"too 80 <br /> Tune Histories B0 <br /> 70 <br /> 00 <br /> o goo .00 s0o a0o foo0 <br /> F w1mcT 1Ne1 <br /> After Si kW mW Summers,(1974) Fourier Fregoemy Spectra <br /> Figure 3.4—Effects of Weighted Filtering on Air-overpressure Records <br /> The regulatory limit defined by USBM, as adopted in State of Colorado regulations, for air- <br /> overpressure measured with 2-Hz response seismographs is 133-dBL(0.014 psi).Damage to old <br /> or poorly glazed windows does not occur until air-overpressure reaches about 150 dBL. More <br /> importantly, since the decibel scale is a logarithmic ratio,the actual overpressure at 150 dBL is <br /> 0.092 psi, versus 0.013 psi at 133 dBL. Therefore, the actual pressure at the 133-dBL limit, is <br /> over seven times (0.0917/0.0129) lower than the threshold damage level at 150-dBL. The <br /> relationships between actual overpressure expressed in psi and decibel scale measurements are <br /> shown in the following Equations. NOTE: Due to the logarithmic ratios used to decibel values, <br /> seemingly small changes in decibel readings can equate to large changes in absolute <br /> overpressure(psi). <br /> 0=20 Log10 PI, or P=P 10���°/ Equation 3.1 <br /> / o <br /> Where:dB=decibels.P=overpressure(ps),Po=Threshold of Human Hearing Pressure(20 microPascals or 2.9 x 10,9 psi). <br /> REVEY Associates,Inc. Page 8 April 20M <br />