Environmental Engineering Reference
In-Depth Information
2.4.4 Explosion Effect of Liquid Explosives Under Water
2.4.4.1 Physical Phenomena of Explosion Under Water
When the loaded explosives explode under/in the unlimited water, the pressure of
high-temperature and high-pressure products is much higher than hydrostatic
pressure of water. So when liquid explosives explode under/in water, both shock
waves and bubble pulse phenomena are produced. In physical properties, air and
water have both similarity and difference. The explosion of liquid explosives in
water has not only similar physical phenomena with that in air, but also different
ones. The main difference is in three aspects: (1) For the explosion with same
amount of explosives, the pressure of shock waves in water is much bigger than that
of air shock waves, (2) The impact time of shock waves in water is much shorter
than that of air shock waves, and (3) The propagation rate of air shock wave fronts
is faster than that of front sound; while the propagation rate of shock waves in water
is approximately front sound rate. The main reason for the difference is that water is
noncompressible. Experiments indicate that volume change of water is 1/320 from
7.5 to 10.0 MPa. The density change of water is
05 at 100 MPa. But
under extremely high pressure, water is compressible. So water shock waves are
produced under the high pressure of explosion products. The density of water is
much larger than air. The hydrostatic pressure is different if the explosion is in
different depth. The expansion of products in water is much slower than in air. The
sound rate in seawater with 18
D
q=q
0
:
C is about 1,494 m/s, higher than that in air. The
sound rate in water changes if the gas amount in the water is different. When the air
occupancy is 0.1
°
1 %, the sound rate in water drops to 900 m/s. While when the air
occupies 6 %, the sound rate in water decreased to 500 m/s. From here we see that
the explosion of liquid explosives under/in water is much complex than in air.
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