Laserfiche WebLink
Rule 6.5 <br />• Both governmental agencies and private sector investigators have conducted considerable. <br />research to determine how ground motion might influence the stability of rock and soil <br />structures, or cause damage to typical structures. For instance, from U.S. Bureau of <br />Miries studies (Bulletin 656, 1979 and RI 8507, 1980) researcher have recommended <br />conservative criterion that most government agencies, including Colorado, have adopted <br />in commercial blasting regulations. To prevent blast-induced ground motion from even <br />approaching damage thresholds, these regulations establish extremely cautious limits on <br />peak particle velocity (ppv). Some damage prevention regulations also consider the <br />frequency of ground motion. Other researchers have evaluated the effects of ground <br />motion on people, buried pipelines, water wells, and 'many other structures. In this <br />investigation, Rio Grande has analyzed the potential risk of blast-induced vibration <br />damage or disturbances to structures and persons located near the Red Rock Surface <br />Mine. <br />Potential for Damage to structures from Blast-Induced Ground Motion: <br />The United States Bureau of Mines, in RI8507 (1980) made the following conclusions <br />regazding the potential for damage caused by blast-induced ground motion. <br />"Practical safe criteria for blasts that generate low frequency ground vibrations are 19 <br />nm/s (0.75 in/s) for modern gypsum board houses and 12.7 nm/s (0.50 in/s) for plaster on <br />lath interiors. For frequencies above 40 Hz, a safe particle velocity maximum of Sl nm/s <br />• (2.0 in/s) is recommended for all houses. <br />It should be noted that the USBM RI 8507 recommendations are designed to prevent <br />even threshold damage in residences of lower-quality construction. Threshold damage <br />was defined as follows: <br />"Threshold damage was defined as the occurrence of cosmetic damage; that is, the most <br />superfrcial interior cracking of the type that develops in all homes independent of <br />blasting. " <br />In an eazlier USBM study (Bulletin 656, Nichols et al., 1971), it was concluded that if at <br />least 8 milliseconds of delay time separates charges, their effect on ground motion is not <br />cumulative. The "8-millisecond rule" remains as industry and regulatory standard for <br />defining "separate" delays. <br />Blasting researchers, over many years, have developed and verified the validity of using <br />scaled relationships to predict vibration intensity at various distances. These relationships <br />use scaling theory to define the relationship between ground vibration particle velocity, <br />chazge weight, and distance. Distance is scaled by the squaze root of chazge weight to <br />create a single dependent vaziable called scaled distance (SD). Various forms of this <br />relationship are shown below: <br />• ppv = K(SD)"' and SD=D/~W <br />Where: ppv = Peak Particle Velocity (inch/sec.) <br />APP~ibi7sA-7-APP(ll80)ReJ8J7anoary 17, 2002 '~ <br />