A History of Research and a Review of Recent Developments

38
The detonation of explosive charges
ground shock induced peak overpressure (p 0 in psi) and scaled burial depth
lay broadly within the band shown in Fig 2.12.
Much attention was given in the 1960s to the possibility of deep underground
nuclear test explosions to avoid fall-out problems, occurring at such a depth
that the only effects at ground level were associated with the propagation of
elastic stress waves through the soil. To support the UK investigations a
theoretical report on deep underground explosions was written by Chadwick,
Cox and Hopkins [2.14]. One of the reasons for their study was that, although
Hopkinson’s size scaling law (which has been used extensively so far in this
chapter) gives satisfactory results in most instances, there is a problem for
scaling the crater size of very large nuclear explosions when the effects of
gravity are no longer negligible. Thus craters from nuclear explosions become
relatively more shallow as the explosion size increases. Further, the onset of
plastic flow in a soil, as described by Coulomb’s law of failure, means that the
resistance to movement of a soil undergoing plastic deformation will increase
with depth.
Figure 2.12 Experimental relationship between ground shock induced peak
overpressure (p 0 ) and scaled burial depth, for a scaled ground range of 5 ft/lb 1/3
(from Vortman, ref 2.13).