Useful
Conversion Factors for Blasters:
Official Metric Equivalents
(according to
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)
(π = 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