A History of Research and a Review of Recent Developments

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Simulation of loads on underground structures 135 described in section 6.2 were fitted with test sections in which the travelling shock front passed over a mass of soil. Various model structural forms could be built within the mass, and subjected to shock loading via the soil cover. A typical example of this arrangement was the blast simulator at Foulness Island in the UK, where a short length of the 8 ft diameter section ran over a tank of soil. At this point the lower wall of the simulator tunnel was removed so that the shock front ran transversely over the soil surface. A cross section of the tube at the test zone was given in an earlier book by the author, Bulson [6.37], and is reproduced here in Figure 6.9. Similar arrangements were made in horizontal blast simulators in Europe and the USA. A second type of test apparatus, for smaller-scale work, was to use a vertically mounted shock tube, the open lower end of which was set immediately above a mass of soil. The initiation of a shock wave resulted in the application of an instantaneous pressure vertically over the surface of the soil. Simple model structures could be buried in the soil, and the loading on them inferred from strain and acceleration records. A vertical shock tube facility of this type was also built at Foulness, and has been described in a report by Clare [6.38]. The author used this shock tube to apply loads to buried thin-walled cylinders, and the experiments are described in reference [6.37]. The shock tube was 40 feet long, 2 feet in diameter, and was fired by a coiled charge of cordtex at the top. Clare showed that the blast pressure-duration relationship closely followed the Friedlander form. The soil tank introduced under the lower opening of the tube was 5 feet square, and the test structures were set in various soils so that they could be viewed through tunnels. High speed cine-film was taken through the tunnels of each collapse sequence. The firing procedure was first to set the Figure 6.9 Cross section of shock tube at the test zone (Foulness, UK) (UK Atomic Weapons Research Establishment, 1980) (from Bulson, ref. 6.37).
136 Pressure measurement and blast simulation camera working by electrically operated remote control from a blast proof building a short distance from the rig; a few milliseconds later the camera operated an electrical charge-firing circuit. The moment of firing was recorded by a flash on the film from a photoflood bulb operated by the firing circuit. The camera speed was 3000 frames per second, with a running time of about 3 sec, including acceleration and deceleration. The time interval from firing to complete decay of the blast pressure was about 20 msec. Blast pressures in the tube were measured by piezo-electric gauges. A dimensionally similar vertical shock tube was constructed at the US Air Force Weapons Laboratory, Kirkland, New Mexico, in the 1960s, and has been described by Abbott [6.9]. Detonation was by means of 4.57 lb of primacord, and the shock pressure was applied to a cylindrical soil bin 48 in high, 22 in diameter. Another type of vertically set apparatus for simulating blast loads was built at the US Waterways Experiment Station at Vicksburg, Miss. USA, and has been described briefly by Flathau, Dawsey and Denton [6.39]. It consisted of a vertical cylinder, containing a piston that could be hydraulically actuated to provide short duration concentrated loads over a maximum stroke of 4 in. Tests showed that loads in excess of 200 000 lb could be applied with a minimum rise time of 1.3 msec with a movement of about 0.25 in of the loading ram. A second version of this vertical loading system, operated in a similar way, was capable of applying loads of 500 000 lb over a time of 80 msec. Figure 6.10 Large blast load generator at the Waterways Experiment Station, USA (from Flathau et al., ref. 6.39).
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EXPLOSIVE LOADING OF ENGINEERING ST
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Explosive Loading of Engineering St
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Contents Preface vii Acknowledgemen
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Preface A long time ago I walked ov
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Acknowledgements The reports from w
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xii Notation m mass of projectile m
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xiv Notation Q work done during exp
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Introduction Explosions can threate
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Introduction xix Bertram Hopkinson
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Introduction xxi in the seventeenth
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Introduction xxiii own versions of
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Introduction xxv indoor shelters an
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Introduction xxvii explosions/ stru
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Introduction xxix particularly dama
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Introduction xxxi but the feeling i
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2 The nature of explosions propelli
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4 The nature of explosions or rathe
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6 The nature of explosions ogive, a
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8 The nature of explosions mass, an
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10 The nature of explosions Figure
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12 4 lb cylinders, TNT, 3.75 lb sph
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14 The nature of explosions As Figu
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16 The nature of explosions of the
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18 1.4 THE DECAY OF INSTANTANEOUS O
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20 The nature of explosions Figure
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22 The nature of explosions where I
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24 sometimes written in psi as The
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26 The nature of explosions 1.20 Ki
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28 The detonation of explosive char
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50 Figure 2.18 Radius/time curve of
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54 and 50%, rather than by a factor
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3 Propellant, dust, gas and vapour
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Dust explosions 61 as the period 19
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Gas explosions 63 reported by Palme
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Gas explosions 65 workings in very
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Vapour cloud explosions 67 the leak
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References 69 in Los Angeles Harbou
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4 Structural loading from distant e
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Uniformly distributed pressures 73
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Table 4.1 Loading/time relationship
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Loading/time relationships 77 overp
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Loading/time relationships 79 side
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Loads on underground structures 81
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Loads on underground structures 83
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Page 122: References 89 4.12 Allgood, J. (197
Page 125 and 126: 92 Structural loading from local ex
Page 131 and 132: 98 The general empirical equation f
Page 133 and 134: 100 Structural loading from local e
Page 145 and 146: 112 Figure 5.16 Relationship betwee
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Page 167: 134 Pressure measurement and blast
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Page 179 and 180: 146 Penetration and fragmentation w
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Page 185 and 186: 152 Penetration and fragmentation n
Page 191 and 192: 158 Figure 7.16 Penetration simulat
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Page 197 and 198: 164 Table 7.1 Penetration and fragm
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Page 217 and 218: 184 The effects of explosive loadin
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186 The effects of explosive loadin
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188 Table 8.1 It is worth noting th
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200 Table 8.5 The effects of explos
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216 Response, safety and evolution
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224 In the log-normal distribution
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230 Cole, R.H. 46, 48, 53, 55, 99 C
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232 Petry 143 Philip, E.B. 13, 14,
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Subject index Aircraft damage 207 A
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A History of Research and a Review of Recent Developments

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