摘要:

Investigation results on shock metamorphism of rock taken from the environs of the natural meteoritic crater Ja¨nisja¨rvy, Karelia, Russia, before and after its spherical explosive compression in the laboratory‐scale experiments, are presented. Elements migration in stress‐wave of increasing along the radius intensity in the solid state, as well as peculiarities of melting of polyminerals rock on isentropes under rarefaction and at the Hugoniots have been observed. A correlation has been established between main characteristics of shock melt glasses, obtained in rock samples of the Ja¨nisja¨rvy crater at meteoritic impact and during explosive laboratory‐scale experiments. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780513

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Baneberry, a 10‐kiloton nuclear event, was detonated at a depth of 278 m at the Nevada Test Site on December 18, 1970. Shortly after detonation, radioactive gases emanating from the cavity were released into the atmosphere through a shock‐induced fissure near surface ground zero. Extensive geophysical investigations, coupled with a series of 1D and 2D computational studies were used to reconstruct the sequence of events that led to the catastrophic failure. However, the geological profile of the Baneberry site is complex and inherently three‐dimensional, which meant that some geological features had to be simplified or ignored in the 2D simulations. This left open the possibility that features unaccounted for in the 2D simulations could have had an important influence on the eventual containment failure of the Baneberry event. This paper presents results from a high‐fidelity 3D Baneberry simulation based on the most accurate geologic and geophysical data available. The results are compared with available data, and contrasted against the results of the previous 2D computational studies. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780514

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Analyzing the high energy proton diffusion through solid matter rigorously, by using the transfer equation, means to tackle many difficulties most of which arise from the long range nature of the Coulomb interactions, involving more than one particle simultaneously. The commonly used approach of neglecting the multi‐body collisions, though correct for rarefied neutral gases, often leads to very poor approximations, when charged particles moving through dense matter are considered. Here we present a numerical simulation of the Fokker‐Planck equation where the multi‐body collisions are taken into account. The model allows to calculate point‐wise the distribution of energy and momentum transferred to the target. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780515

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We present preliminary results from a parameter study investigating the stability of underground structures in response to explosion‐induced strong ground motions. In practice, even the most sophisticated site characterization may lack key details regarding precise joint properties and orientations within the rock mass. Thus, in order to place bounds upon the predicted behavior of a given facility, an extensive series of simulations representing different realizations may be required. The influence of both construction parameters (reinforcement, rock bolts,liners) and geological parameters (joint stiffness, joint spacing and orientation, and tunnel diameter to block size ratio) must be considered. We will discuss the distinct element method (DEM) with particular emphasis on techniques for achieving improved computational efficiency, including the handling of contact detection and approaches to parallelization. We also outline the continuum approaches we employ to obtain boundary conditions for the distinct element simulations. Finally, our DEM code is used to simulate dynamic loading of a generic subterranean facility in hardrock, demonstrating the suitability of the DEM for this application. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780516

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The use of stress gauges for characterization of the shock behaviour of porous materials is an important tool for the description of non‐equilibrium response in shock compression. The present paper demonstrates that gauge measurements can be employed for both dry and hydrated sand. In a previous publication [Resnyansky, A. D.,et al.J. Appl. Phys. 2003], a single‐phase rate sensitive model was employed to describe tests for dry sand. In the present paper a two‐phase model has been developed, which allows us to describe the dry and hydrated sand with a uniform approach. Specification of the material is achieved by involving air or water as a matrix material in a two‐phase representation of the sand. The effect of the gauge embedding on the stress profiles is analysed numerically to understand features of the test records. Comparison of experimental and numerical results demonstrates a good agreement. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780517

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Collisions on icy planetary bodies produce impact melt water, redistribute ground ice, and deposit thermal energy available for chemical reactions. The amount of melt generated from an impact is sensitive to the initial temperature, which ranges from the 273 K on Earth and Mars to 40 K on the surface of Pluto. Previous shock wave studies, centered at ∼263 K for terrestrial applications, had difficulty defining the onset of phase transformations on the ice Hugoniot, and consequently, the criteria for shock melting was poorly constrained. Because ices on most planetary surfaces exist at ambient temperatures much below 263 K, we conducted a detailed study of the shock response of solid ice at 100 K and ∼40 &percent; porous ice at ∼150 K to derive Hugoniots and critical pressures for shock‐induced melting that are applicable to most of the solar system. New Hugoniots for solid and ∼40 &percent; porous ice are defined, and the critical pressures required to induce incipient melting and complete melting upon isentropic release from the shock state are revised using calculated shock temperatures and entropy. The critical pressures required for incipient melting of solid ice are only 0.6 and 4.5 GPa for 263 and 100 K respectively, and pressures between 0.1–0.5 GPa initiate melting of porous ice between 250 and 150 K. Therefore, hypervelocity impact cratering on planetary surfaces, with peak shock pressures >100 GPa, and mutual collisions between porous cometesimals in the outer solar system, with peak pressures of ∼1 GPa, will generate prodigious amounts of shock‐induced melt water. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780518

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

All fresh and many older Martian craters with diameters greater than a few km are surrounded by ejecta blankets which appear fluidized, with morphologies believed to form by entrainment of liquid water. We present cratering simulations investigating the outcome of 10 km s−1impacts onto models of the Martian crust, a mixture of basalt and ice at an average temperature of 200 K. Because of the strong impedance mismatch between basalt and ice, the peak shock pressure and the pressure decay profiles are sensitive to the mixture composition of the surface. For typical impact events, about 50&percent; of the excavated ground ice is melted by the impact‐induced shock. Pre‐existing subsurface liquid water is not required to form observed fluidized ejecta morphologies, and the presence of rampart craters on different age terranes is a useful probe of ground ice on Mars over time. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780519

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A series of plate impact experiments was performed on cement paste and mortar. Longitudinal stresses were measured using embedded manganin stress gauges up toca.18 GPa. Data are then compared to those obtained in previous studies on concrete varied on aggregate size using a plate reverberation technique and velocity interferometry. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780520

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Plate impact experiments have been performed on the igneous diamond‐bearing matrix kimberlite. Longitudinal and lateral stresses were measured in the uniaxial strain regime using manganin stress gauges. The shock Hugoniot of the kimberlite has been characterized at axial stresses between 1 and 9 GPa. The kimberlite has a low impedance response when compared with similar data for other geological materials. The data indicate that the rock behaves inelastically above shock stresses of 1 GPa. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780521

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Au redistribution induced by 13.5 GPa shock was studied in cylindrical geometry of explosive loading of porous mixture of quartz and pyrite with Au+radionuclide195Au. Part of Au was evaporated and precipitated on the surfaces of minerals. Maximal concentration was detected in siliceous melt in the bottom of the capsule that can be explained by “snowplow” motion (or jetting) of gold vapor in front of Mach shock. In direction perpendicular to axis the distribution of Au had a “wavy” character probably due to preferential diffusion of Au vapor along shear bands. Evaporation of Au can only be explained by highly nonequilibrium energy release in porous mixtures. These data may be useful in understanding of the mechanism of anomalous concentration of Au and other elements in the impact structures in nature. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1780522

出版商:AIP    

年代:1904

数据来源: AIP