Nuclear Decoupling, Full and Partial

Patterson, Dan W.

doi:10.2172/4633626

Cited by 11 publications

(18 citation statements)

References 3 publications

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“…The effects of small cavities, however, has received much less attention than those of almost or fully decoupled tests. The theoretical studies of Patterson [1966] indicate that substantial decoupling factors are achieved even when the cavity radius is significantly smaller than that required for full decoupling. He did not investigate, however, cavities with scaled radii smaller than 14.5 m/kt 1/3.…”

Section: Testing Of Underground Nuclear Explosions Under the Provisiomentioning

confidence: 99%

The effective yield of a nuclear explosion in a small cavity in geologic material: Enhanced coupling revisited

King¹,

Freeman²,

Eilers³

et al. 1989

J. Geophys. Res.

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The hydrodynamic yield of an underground nuclear explosion in a small cavity has been recalculated using computer modeling. We have considered explosions in spherical cavities having scaled radii, R/W1/3, less than 3.5 m/kt1/3 (R is the cavity radius in meters and W is the explosion energy in kilotons) in quartz (SiO2) using an available equation of state (Ree, 1976). These calculations show, at a scaled radius of ≈1.5 m/kt1/3, a maximum hydrodynamic yield substantially greater than that of an explosion in a tamped cavity (enhanced coupling) as measured by the shock time of arrival in the near field. These results are in qualitative agreement with those of earlier investigators who utilized the reduced displacement potential to evaluate coupling. We found, however, that the coupling coefficient (ratio of yield for cavity model to yield for tamped model) is significantly reduced when an improved quartz equation of state is employed. We also calculated enhanced coupling in two additional geologic materials, salt and tuff. All of the calculations mentioned above (including our initial ones) were simplified through the omission of significant thermal radiation contributions to energy and pressure in the cavity and the diffusion by photon transport of energy from the explosion cavity into the adjacent rock. When we take these processes into account, we find that for a cavity radius of approximately 1.5 m/kt1/3, near the peak of enhancement for our models with no radiation, there is instead a decoupling of about 15% in SiO2, 20% in tuff, and about 15% in salt. At the largest scaled cavity radius considered, 3.42 m/kt1/3, there is a decoupling of 40% in SiO2, 35% in tuff, and 35% in salt. For all three media the coupling coefficients decrease monotonically as the cavity radius increases. This result is different from previous ones in which the radiation terms were neglected. The radiation processes not only provide another method for vaporization of the rock but also change the effective gamma of the cavity gas as a result of the reduced cavity temperature and the addition of radiation pressure and energy terms. We have also found that the major effect on coupling is due to the contribution of radiation to the equation of state. Computer calculations which omitted radiation diffusion showed that the major change in effective coupling is due to the radiation energy and pressure modifications of the equation of state and to the corresponding changes in the effective gamma of the cavity gas. Thus, while the radiation diffusion is responsible for minor changes in the coupling curves, the main trend of these curves does not depend on diffusion.

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Section: Testing Of Underground Nuclear Explosions Under the Provisiomentioning

confidence: 99%

The effective yield of a nuclear explosion in a small cavity in geologic material: Enhanced coupling revisited

King¹,

Freeman²,

Eilers³

et al. 1989

J. Geophys. Res.

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“…The functions C mn (r, p, q) and S mn (r, p, q) of three arguments are the real and imaginary parts of the known integrals % 1 2 3 4 5 6 7 8 9 10 11 Gnome 3.1 [15] 360 [16] 2200 [11] 4080 [11] 3120 [17] 2740 [11] 0.17 [11] 1040 895 82 4.4 7.0 6.0 Salmon 5.3 [18] 828 [18] 2240 [15] 4670 [19] 3700 [18,19] 3770 [14] 0.06 [14] 700 719 57 14.4 3. 2 3.3 which are expressed explicitly as C 00 (r, p, q) = M/R, S 00 (r, p, q) = N/R,…”

Section: Rayleigh Wavementioning

confidence: 99%

Movement of the ground in Rayleigh waves produced by underground explosions

Симоненко

Shishkin

Шишкина

2006

J Appl Mech Tech Phys

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Analytic representations are obtained for the displacement and stress fields in the Rayleigh surface wave (R-wave) generated in an elastic half-space by an internal source that produces the same seismic P -wave as an underground explosion. Oscillograms, particle trajectories, and stresses in the halfspace and on its surface are calculated. Relations for the energy flux in the R-wave are obtained. For rock salt, the fraction of the explosion energy transferred to the R-wave is estimated. It is established that this fraction can reach values of about 1% of the total explosion energy if the explosion is a contained one. As the charge depth is increased, the energy of the R-wave decreases in approximately inverse proportion to the depth.Introduction. Elastic surface Rayleigh waves (R-waves) [1] result from dynamic actions on the surface of elastic bodies. In structures of small dimensions, they are used as ultrasonic waves. Rayleigh waves are also observed in large structures and engineering constructions. In addition, R-waves are produced by explosions, earthquakes, and impacts of cosmic bodies on the planets. Seismic R-waves are used to probe the Earth's crust and to study its structure, and long R-waves are used to study the Earth's mantle. Rayleigh waves produced by explosions contain a significant fraction of the explosion energy, and at a certain distance from the epicenter, they dominate the other seismic waves. They contain information on the energy source and the properties of the medium. For example, records of R-waves from some underground nuclear explosions suggest that spall fracture of the medium occurs at the epicenters of the explosions [2]. In [3], it is shown that during impacts of cosmic bodies on the Earth, the focusing of R-waves in the antipode region (the region opposite to the site of impact) can lead to the formation of unusual geological structures such as explosion pipes or diatremes.Rayleigh waves produced by a point source in an elastic half-space were considered in [4][5][6]. Petrashen' [7] studied the Lamb problem for the case of an isotropic elastic sphere and obtained expressions for Rayleigh waves on the surface of an elastic sphere. Onis'ko and Shemyakin [8] studied the movement of the ground surface for an explosion in a half-space, and Alterman and Abramovici [9] explored the movement of the surface of an elastic sphere for a contained explosion. Brekhovskikh [10] investigated Rayleigh waves produced by a harmonious source and propagating along the curved surface of an elastic body. The present paper gives more detailed results for Rayleigh waves on both the surface of an elastic half-space and inside it for explosions at a great depth. The energy flux transferred by the Rayleigh wave is considered, and the fraction of the explosion energy converted into the R-wave energy is estimated. Such data are required to obtain more exact estimates of the damage to various engineering constructions from R-waves and describe the dynamic geological processes occurring in the regions that are ...

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“…Herbst et al [1961] found that the cavity-pressure histories for the Cowboy series of chemical explosions are approximated by a step function plus an impulse function. Patterson [1966] showed that a cavity-pressure step function is a good approximation for nuclear explosions in cavities. Healy et al [1971] showed that a step pressure function in a spherical cavity is a good first approximation to the I•ODEAN seismic-source functions of both the tamped Salmon and the decoupled Sterling explosions.…”

Section: The Explosion Modelmentioning

confidence: 99%

“…The seismic coupling efficiencies E,/E• (Table 3) are an order of magnitude smaller than the upper limit •calculated by means of equation 20 for granite (Table 2) and are somewhat smaller than the granite coupling efficiency given in the Sipri [1968] report (see Table 2). The Fourier amplitudes of •X (t)/Ot presented in Figure 9 are for the elastic-radius step change in cavity-pressure models of the calculated Nevada (A) and Sahara (C) explosions, if we use data given in Table 3 and /Value of 4000 m 3 given for the reduced displacement potential by Patterson [1966]. possible overlap at comparable seismic-wave energies within the 0.5-to 5-Hz band is probably not sufficient to account for the (apparently) similar seismic coupling shown in Figure 7.…”

Section: Of the $Ipri [1968] Report) On The Other Hand The Differenmentioning

confidence: 99%

An energy approach to seismic coupling analysis

Rodean¹

1972

J. Geophys. Res.

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The explosion process is modeled by a step change in cavity pressure. The cavity is assumed to be spherical and embedded in an ideal elastic solid. This model represents a fully decoupled explosion in a cavity. It can also be used as an equivalent seismic‐wave source representing a tamped explosion. A decoupling cavity existence and operating region is defined in terms of cavity and overburden pressures and the rock yield strength. The upper limit for seismic coupling efficiency for an ideal monoatomic gas is given by Ew/Ex = 2Y/3μ, where Ew is the radiated seismic‐wave energy, Ex is the explosion yield, Y is the rock yield function, and μ is the shear modulus. This equation may be a good approximation for the seismic‐coupling efficiency of a tamped explosion, because it agrees well, perhaps fortuitously, with observations for tamped nuclear explosions in salt and granite. The seismic‐energy radiation from a spherical cavity in an elastic medium is given by Ew = 2πPχ, where P is a step change in cavity pressure and χ is the final value of the reduced displacement potential. This equation shows that the seismic‐coupling efficiencies of French nuclear explosions in Sahara granite may be about equal to those of U.S. shots in Nevada granite, even though the cavity radii, elastic radii, and reduced displacement potentials for these two sets of explosions (assuming equal yields) are quite different. The theoretical seismic‐energy spectra for the Nevada and the Sahara explosions are consistent with the measured spectrum for the 5‐kT Hardhat explosion and overlap to a significant degree. This overlap is centered in the 0.5‐ to 5‐Hz bandwidth and may partially explain why nuclear explosions in Nevada and Sahara granites appear to have the same magnitude‐yield relation. The possibility of regional variation of seismic‐signal attenuation in the upper mantle of the United States and the Sahara should also be investigated to complete the explanation of seismic coupling in Nevada and Sahara granite.

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Nuclear Decoupling, Full and Partial

Cited by 11 publications

References 3 publications

The effective yield of a nuclear explosion in a small cavity in geologic material: Enhanced coupling revisited

The effective yield of a nuclear explosion in a small cavity in geologic material: Enhanced coupling revisited

Movement of the ground in Rayleigh waves produced by underground explosions

An energy approach to seismic coupling analysis

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