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Blasting Impacts and Rock Slope Stability Asses went for Cottonwood Quarry in Gram County, CO <br />3.5 Blast Vibration Intensity Predictions <br />It is standard practice to use scaling relationships to predict vibration intensities at various <br />distances. These relationships, based on similitude theory, are used to develop empirical <br />relationships between ground vibration particle velocity, charge weight, and distance. Distance is <br />scaled by dividing it by the square root of the maximum charge weight firing at any time within a <br />blast. This single scaled distance variable can than be used to predict vibration intensity (PPV). <br />The scaling relationship between peak -particle -velocity (PPV) and scaled distance (Da) is shown <br />below in Equation 3.2. <br />In <br />PPV = K(Y-,r or PPV = K (Ds r Equation 3.2 <br />Where: PPV = Peak Particle Velocity (in/s) <br />D = Distance (ft) <br />W = Maximum Charge -weight -per -delay (]b) <br />K = Rock Energy Transfer Constant a( Factor) <br />m =Decay Constant <br />D, = Scaled Distance (m -kgs) <br />Site-specific constants, K and m, can be determined by performing a regression analysis of <br />multiple peak particle velocity (PPV) and D. data pairs. In simple terms, for any given site, K is a <br />measure of how much vibration energy is transferred to the ground near the explosive charge and <br />m defines how fast the energy attenuates with distance. <br />A sample regression curve that was recently prepared by the author to support blasting controls <br />for an upcoming subway project in New York City is shown in Figure 3.4. When plotted in log - <br />log scale, the exponential relationship between scaled distance and PPV generally follows a <br />straight line with a negative slope (m) -- usually around —1.6, and Y -intercept (A) values varying <br />between 960 and 26, as defined by Oriard (1972). The % value (amount of energy at the source) <br />is higher when charges are more confined and/or rock has a high stiMess ratio (Young's <br />modulus of elasticity). <br />REVEY Associates, Inc. Page 9 April 2004 <br />