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Rocky Mountain Asphalt <br />January 20, 1989 <br />Page 4 <br />The D/lr is termed the "scaled distance." The other site constants are <br />generally developed from site-specific data. The Bureau of Mines, however, <br />presents data from numerous blasts which suggest conservative estimates (i.e. <br />values that will produce the most vibration with distance) for the factors, <br />assuming gravity-loaded ANFO is being used as a blasting anent. These estimates <br />are: t) H = 234, and 2) 8 = -1.62, both defined In terms of dlstance in feet and <br />pounds of explosive. Using these values, the previous equation becomes: <br />V = 234 (D/yam)-~•ez <br />This equation can be used to predict peak particle velocity'~in terms of <br />distance from a blast. If, as discussed earlier, we limit the particle velocity at <br />a specific dlstance to less than some value, then a relationship can be developed <br />between the distance to a point and the maximum pounds of explosive per delay <br />in a blast. The limiting particle velocity should be the upper limit of the "Barely <br />Perceptible" range presented previously. Based on these criteria, the maximum <br />pounds of explosive per blast delay (i.e. the total pounds of explosive detonated <br />at one time from one or several blastholes during a particular delay sequence in <br />an blasting pattern) have been calculated for various distances from a blast. For <br />this analysis, the value of the maximum allowable particle velocity has been <br />assumed equivalent to the upper limits of the Barely Perceptible range of 0.225 <br />in/sec. Using this limiting velocity and the conservatively estimated values of B <br />and H, the following limits can be placed on pounds of explosive detonated per <br />delay during production blasting to minimize vibrations at various distances from <br />a blast: <br />Schnabel Engineering <br />