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 (in ft) from the detonating charge

Formula for estimating blast vibration:

PPV = K x (Distance / Weight1/2)-1.6

Where:                  PPV = Peak Particle Velocity (in inches/second)

K = factor that varies with ground conditions, powder factor,

explosive confinement, etc.

Distance = distance (in ft) from the detonating charge

Weight = weight (in lbs) of the detonating charge

Important:             When determining Weight, count all explosives detonating within

any 8 millisecond time period.  Use the highest quantity found

in the blast.

Use a factor K that most closely approximates blast conditions.

Lew Oriard indicated that K can range from a low of approximately24

to a high of approximately 240.  The DuPont Blaster’s Handbook

indicates that a K of approximately 160 would be average.  For blasts

early in the program, use a number higher than normal.  Adjust it

downward only after more experience (and confidence) is gained.

The vibration regression factor -1.6 is the average that can be expected.

It will be greater closer to the blast where body waves dominate and

lower at large distances where surface waves dominate.

Bear in mind that these are estimates only.  Results may vary considerably,

depending upon local conditions and possible errors in measurement.

Golden West Chapter