A History of Research and a Review of Recent Developments

Underwater explosions 45
Table 2.4
The distance from the centre of an underground explosion at which the face of
a tunnel or trench would no longer suffer any disruption is known as the radius of
rupture, R r. Early British military handbooks on mining suggested that
R r =F · W 1/3 feet,
(2.13)
where the soil factor, F, is given in Table 2.4.
British tests during the Second World War suggested that the above figures
were well on the safe side, and that the radius of rupture could safely be
assumed to be 80% of that calculated from Eq. (2.13).
2.4 UNDERWATER EXPLOSIONS
The understanding of explosions that originate below the surface of the sea
owes much to naval research and development of underwater weapons such
as mines, depth charges and torpedoes. We are told that the first recorded
uses of explosives to damage vessels at or below the waterline were at the
siege of Antwerp in 1585 (Dutch v Spaniards) and at La Rochelle in 1625
(British v French), but these were essentially delayed-action floating bombs
rather than true underwater devices. During the American Revolutionary War
in the late eighteenth century mines were attached to ships below the waterline
by a screw, and at the same time Bushnell developed a simple contact mine
which was fired by a gunlock actuated when struck by the enemy ship. Further
developments were recorded during the nineteenth century, and probably fused
mines were used defensively during the Crimean War. The elementary fuses
were glass tubes of sulphuric acid which were broken by impact with the hull
of a ship. The acid mixed with chemicals to develop enough heat to cause the
main charge of gunpowder to explode. By the First World War naval mines