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_ aL~ <br />'• <br />VELOCITY PROBABLE DEGREE OF DAMAGi; <br />2.0 inches per seco~ld---------Recoznnended limit for blasting <br />vibra*_ions at or near <br />buildings. <br />2.8 - 3.3 inches per second---Lo~.ver limits for the occur- <br />ence of da-nage as found in <br />the majority of cases. <br />5.4 inches per seco~ld---------Less than a 50-50 probability <br />of minor damage (fine <br />plaster cracks, opening of <br />old crac!cs) . <br />7.6 inches per second---------50-50 probability of major <br />damage (falling of plaster, <br />serious cracking). <br />The maximum recording of 0.14 inches per second for <br />ti-~e longit~.~.dirai co~r~2ene t of the 5-20-79 blast recorde3 <br />along the Lourlis Railcii Roa•3 presents approximately 7% <br />of the recommended U. S. BM limit and 14% of the OSM limit. <br />This safe by wide mar~,ia. L should also be noted <br />that the seismograph location was approximately z the distance <br />to the ranch buildings themselves. <br />A generally recommended limit for atmospheric over- <br />pressure is 0.5 lbs. per square inch (psi). This is <br />conservative; overpressures from 0.75 to 1.0 psi or more <br />a.re usually required to break properly mounted Windows. <br />With glass under strain, however, failure has occured <br />with overpressures as low as 0.1 psi. Therefore, we <br />reco~mnend restricting o~re'rpressures to *_he lower value <br />of U.1 psi. In this study, the maximum o•rerpressure <br />W35 7% of our recommended limit aild approximately 6% <br />of the OSiiA maximum for impulsive sound. <br />1. Vibratio~i of the intensity ;neasured in this study <br />ar.~ are perceptable. The human body can feel particle <br />velocities as low as .03 or .04~inch per second. <br />Since -velocities over 2.0 inches p~~r seco~ld a-re <br />required to cause structural damage, ho~.aever, per- <br />ceptibility is obviously not ail indicator of whether <br />or not da;na;;e will occur. <br />2. The ground •ribra`io~1s ca:l be Beard. Because the <br />sound is heard at the same time that the ground <br />motio:l is felt, the eEEect of the blast is emphasized. <br />