This document was originally presented at the Golden West Chapter 1999 workshop.

(Click on the title to open a copy of the document.)

Understanding Blast Vibration and Airblast,

Originally presented at the Golden West Chapter workshops in 2006 and 2007.

*  *  *  *  *  *

Useful Conversion Factors for Blasters:

Official Metric Equivalents (according to U.S. and Canadian law):

1 inch (in.)    =    25.4 millimeters (mm)

1 pound (lb.) =    453.59237 grams (g)

 Distance: feet (ft) x 0.3048 = meters (m) meters x 3.2808 = feet Weight: pounds (lbs) x 0.4536 = kilograms (kg) kilograms x 2.2026 = pounds Peak Particle Velocity: in/sec x 25.4 = mm/sec mm/sec x 0.3937 = in/sec Volume: cubic yards (yd3) x 1.308 = cubic meters (m3) cubic meters x 0.7645 = cubic yards Powder Factor: lbs/yd3 x 0.93 = kg/m3 kg/m3 x 1.6863 = lbs/yd3 Square Root Scaled Dist: ft/lbs1/2 x 0.45236 = m/kg1/2 m/kg1/2 x 2.2106 = ft/lbs1/2 Cube Root Scaled Dist: ft/lbs1/3 x 0.3965 = m/kg1/3 m/kg1/3 x 2.5221 = ft/lbs1/3 Pressure: lbs/in2 x 0.145 = Pascals Pascals x 6.895 = lbs/in2 lbs/in2 x .0000689 = kilobars* kilobars* x 14504 = lbs/in2 feet of water x 0.434 = lbs/in2 lbs/in2 x 2.31 = feet of water

* 1 Bar  =  14.5 lbs/in2

Other Miscellaneous Calculations:

Pounds of explosive loading per foot of borehole  =  D2  x  S.G.  x  0.34*

Where:                  D  =   explosive diameter (inches)

S.G.   =   specific gravity of

explosive in g/cc

*   The factor 0.34 is used to convert g/cc to lbs/cu ft and to calculate

the volume of the explosive charge.  It is the result of the equation,

0.7854  x 12  x  62.4

1728

where:          0.7854 = ¼ of pi

12 = the number of inches in a foot

62.4 = the weight of 1 cu ft of water

in lbs (at approx. 45oF)

1728 = the number of cu in in a cu ft

Displacement of water in a borehole:               H  =  D2 / (D2 – De2)  x  h

Where:                  H  =   final height of water

h  =   initial height of water

D  =   hole diameter

De  =   explosive cartridge diameter

Determine H, the final height of water, and then divide H by the cartridge length

to determine the number of cartridges that will be required to build out of the water.

Square Root Scaled Distance = Distance / Explosive Weight 1/2

Cube Root Scaled Distance = Distance / Explosive Weight 1/3

The following equations express the relationships between Velocity, Displacement, Frequency and Acceleration for sinusoidal waveforms:

Velocity (in/sec)  =  2 π  f  D

Velocity (in/sec)   =  386.1 Gs / (2 π f)

Displacement (inches)  =  V  /  (2 π f)

Acceleration (in/sec2)  =  2 π  f  V

Acceleration (in Gs)  =  (2 π  f  V) / 386.1

frequency (Hertz)  =  V / (2 π D)

frequency (Hertz)  =  A  / (2 π V)

= pi  =  3.14159…..)

Cole’s Formula for determining peak pressure from an explosive

charge detonating underwater (assumed TNT or its equivalent):

P  =  2.25 x 104 (W1/3 / R) 1.14

Where:                  P  =  peak pressure in psi

W =  explosive charge weight in pounds

R  =  distance (ft) from the detonating charge

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