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[en] The Hybla Fair underground nuclear event was conducted by the Defense Nuclear Agency (DNA) to assess the feasibility of using low yield devices to reduce the expense of nuclear weapons effects testing. The economy of low yield tests was facilitated by placing of the test bed chamber closer to the source, thereby allowing the use of a shorter horizontal line-of-sight (HLOS) tunnel than used for higher yield testing. One main design concern for the Hybla Fair event centered around the desire for the radiation environment in the test chamber to be equivalent to that of higher yield tests. This concern imposed a severe constraint on the stemming column design. Studies of the required Hybla Fair stemming configuration, of the phenomenology of ground shock-induced stemming plug formation for low-yield events, of the effects of baffles on the stemming process, and of the integrity of the stemming closure region for the containment of the cavity gases are reported

[en] TENSOR74 is a major revision of TENSOR, a computer code designed to solve stress wave propagation problems in two dimensions. The major physics modifications in TENSOR74 are in the area of constitutive modeling of solid materials. The new models, which are described in detail, take into account pore collapse, ductile and strain softening brittle failure, as well as tensile failure with void opening and closure. In addition, a modified form of linear artificial viscosity is described. (U.S.)

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[en] A model has been devised to calculate shock Hugoniots and release paths off the Hugoniots for multicomponent rocks containing silicate, carbonate, and water. Hugoniot equations of state are constructed from relatively simple measurements of rock properties including bulk density, grain density of the silicate component, and weight fractions of water and carbonate. Release paths off the composite Hugoniot are calculated by mixing release paths off the component Hugoniots according to their weight fractions. If the shock imparts sufficient energy to the component to cause vaporization, a gas equation of state is used to calculate the release paths. For less energetic shocks, the rock component will unload like a solid or liquid, taking into account the irreversible removal of air-filled porosity

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[en] The craters from high-yield nuclear tests at the Pacific Proving Grounds are very broad and shallow in comparison with the bowl-shaped craters formed in continental rock at the Nevada Test Site and elsewhere. Attempts to account for the differences quantitatively have been generally unsatisfactory. We have for the first time successfully modeled the Koa Event, a representative coral-atoll test. On the basis of plausible assumptions about the geology and about the constitutive relations for coral, we have shown that the size and shape of the Koa crater can be accounted for by subsidence and liquefaction phenomena. If future studies confirm these assumptions, it will mean that some scaling formulas based on data from the Pacific will have to be revised to avoid overestimating weapons effects in continental geology. 9 refs., 5 figs

[en] A computational approach used for subsurface explosion cratering has been extended to hypervelocity impact cratering. Meteor (Barringer) Crater, Arizona, was selected for our first computer simulation because it was the most thoroughly studied. It is also an excellent example of a simple, bowl-shaped crater and is one of the youngest terrestrial impact craters. Shoemaker estimates that the impact occurred about 20,000 to 30,000 years ago [Roddy (1977)]. Initial conditions for this calculation included a meteorite impact velocity of 15 km/s. meteorite mass of 1.57E + 08 kg, with a corresponding kinetic energy of 1.88E + 16 J (4.5 megatons). A two-dimensional Eulerian finite difference code called SOIL was used for this simulation of a cylindrical iron projectile impacting at normal incidence into a limestone target. For this initial calculation a Tillotson equation-of-state description for iron and limestone was used with no shear strength. A color movie based on this calculation was produced using computer-generated graphics. Results obtained for this preliminary calculation of the formation of Meteor Crater, Arizona, are in good agreement with Meteor Crater Measurements