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Blasting Impacts and Rock Slope Stability Assessment for Cottonwood Quarry in Grand 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(D.)is shown <br /> below in Equation 3.2. <br /> �` <br /> PPV=K(nw-) or PPV=K(Ds) Equation 3.2'" <br /> Where: PPV=Peak Particle Velocity(in/s) <br /> D=Distance(ft) <br /> W=Maximum Charge-weight-per-delay(lb) <br /> K=Rock Energy Transfer Constant(K-Factor) <br /> m =Decay Constant <br /> Dg=Scaled Distance(m-kg7o-5) <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 K value (amount of energy at the source) <br /> is higher when charges are more confined and/or rock has a high stiffness ratio (Young's <br /> modulus of elasticity). <br /> REVEY Associates,Inc. Page 9 April 2004 <br />