摘要:

Planar impact methods and velocity interferometry diagnostics have been used to measure the spall strength of Solenhofen limestone and Dresser basalt following shock precompression to stresses over the range of approximately 100 to 700 MPa but below the Hugoniot elastic limit of both rock materials. Spall strength and spall fracture energy are determined from the measured spall pullback profiles. Spall strengths of 77 MPa for Solenhofen limestone and 130 MPa for Dresser basalt, independent of impact amplitude, were determined. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303689

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Discovery of abundant anhydrite(CaSO4)and gypsum(CaSO4.2H2O)in the otherwise carbonate sediments comprising the upper portion of the rocks contained within the Chicxulub impact crater has prompted research on the shock-induced vaporization of these minerals. We use a vaporization criterion determined by shock-induced entropy. We reanalyze the shock wave experiments of Yang [1]. He shocked 30&percent; porous anhydrite and 46&percent; porous calcite. Post-shock adiabatic expansion of the sample across a 5 mm-thick gap and then impact upon an aluminum witness plate backed by LiF window that is monitored with a VISAR. Reanalysis uses Herrman’s P-&agr; model [2] for porous materials, and a realistic interpolation gas equation-of-state for vaporization products. Derived values of the entropies for incipient and complete vaporization for anhydrite are1.65±0.12and3.17±0.12&hthinsp;kJ(kg.K)−1,and for calcite these are0.99±0.11and1.93±0.11&hthinsp;kJ(kg.K)−1.Corresponding pressures for incipient and complete vaporization along the Hugoniot of non-porous anhydrite are32.5±2.5and122±13&hthinsp;GPaand for non-porous calcite are17.8±2.9and54.1±5.3&hthinsp;GPa,respectively. These pressures are a factor of 2–3 lower than reported earlier by Yang. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303690

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The temperatures induced in crystalline calcite upon planar shock compression (95–160 GPa) are reported from two-stage light gas-gun experiments. The temperatures are obtained fitting 6-channel optical pyrometer radiances in the 450 to 900 nm range, to a Planck radiation law temperature varied from 3300 to 5400 K. Calculations demonstrate that the temperatures are some 400 to 1350 K lower than if either shock-induced melting and/or disproportionation of calcite behind the shock front was not occurring. Here calcite is modeled as disproportionating into a molecular liquid, or a solid CaO plusCO2gas. For temperature calculations, specific heat at constant volume for one mole ofCO2is taken to be 6.7R as compared to 9R in the solid state; whereas calcite and CaO have their solid state values (15R and 6R). Calculations also suggest that the onset of decomposition in calcite to CaO andCO2during loading occurs at∼75±10&hthinsp;GPa,along the Hugoniot whereas decomposition begins upon unloading from 18 GPa. The 18 GPa value is based on comparison of VISAR measurements of particle velocity profiles induced upon isentropic expansion with one-dimensional numerical simulation. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303691

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A series of plate impact experiments has been performed to determine the shock loading behavior of cement paste (grout) with water to cement ratio of 0.35 by weight and no aggregates. Hugoniot stress data were collected by means of embedded manganin gauges up to 5 GPa. Results are then compared to those obtained in previous studies on concrete varied on aggregate size using a plate reverberation technique and velocity interferometry. Results indicate that the average loading of cement and concrete are comparable. In addition, the in-material gauge technique has the advantage of estimating the cement Hugoniot directly and provides a measurement of the rise times, which were found to be inversely related to impact stresses. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303692

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The dynamic failure behavior of mortar under impact loading is characterized through plate impact experiments. The study concerns the possible existence of failure waves in mortar. The analysis focuses on the spall strength in different regions of impacted specimens and the evolution of longitudinal and transverse stresses under normal impact loading. The diagnostics used are VISAR interferometry for surface velocity measurement and embedded PVDF gauges for internal stress measurement. Experiments conducted do not provide evidence for the occurrence of failure waves. While the study suggests that a threshold impact velocity is required to initiate failure, a clearly defined failure wave that propagates behind the loading wave is not observed. Instead, a gradual failure process initiating at the arrival of the compressive wave is found. This gradual failure process is in contrast to the well-defined failure front in the failure wave phenomenon in glasses. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303693

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We present results from mesoscale modeling of shock recovery experiments on Berea sandstone with the Smooth Particle Hydrodynamics and the Discrete Element methods. Each grain is represented with clusters of Discrete Element particles to provide explicit representation of the grain and pore structure. The grain structures simulate the structures observed using synchrotron micro tomography and Scanning Electron Microscope imaging. The modeling accounts for the influence of pore fluid and illustrates how grain/pore heterogeneity under dry and saturated states affects stress wave and grain damage behavior. The simulations show characteristics of the phenomena observed in recovery experiments. An increase in grain damage coincides with an increase in stress level and pulse duration. The grains in dry samples are extremely and irregularly fragmented with extensively reduced porosity. Less grain damage and higher porosity is observed in the saturated samples. The influence of pore fluid miti-gates the interaction between grains, thus reducing fragmentation damage. This modeling approach in concert with experiments offers a unique way to understand dynamic compaction of brittle porous materials. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303694

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

This paper describes the results of a computational study performed to investigate the behavior of granite under shock wave loading conditions. A thermomechanically consistent constitutive model that includes the effects of bulking, yielding, material damage, and porous compaction on the material response was used in the simulations. The model parameters were determined based on experimental data, and the model was then used in a series of one-dimensional simulations of PILE DRIVER, a deeply-buried explosion in a granite formation at the Nevada Test Site. Particle velocity histories, peak velocity and peak displacement as a function of slant range, and the cavity radius obtained from the code simulations compared favorably with PILE DRIVER data. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303695

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The ultimate objective of seismic exploration is to obtain reasonable estimates of the subsurface properties of rocks and fluids. A space-time algorithm is formulated that estimates the relative changes in subsurface density, bulk modulus, and shear modulus from the amplitude changes in the reflected compressional wave data as a function of offset. This is accomplished by transforming the elastic wave displacement equation into pressure-stress coordinates, where the Born approximation of the Lippman-Schwinger equation in the Fourier-transform domain is employed to decompose the observed fields into their compressional- and shear-wave scattered components. An inversion algorithm to generate physical properties is developed from the resulting angular-dependent reflection coefficients for each of the scattering modes. The relative change in bulk modulus indicates the presence of reservoir rocks containing hydrocarbons, the relative change in shear modulus indicates the rigidity of the reservoir rock, and the relative change in density delineates regions of high hydrocarbon concentration. Inverted data from the Gulf Coast are in good agreement with borehole data. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303696

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Propagation of shock waves in layered anisotropic tectonic media is associated with their fronts transformation, scattering, bifurcation and focussing. To investigate these phenomena, a technique based on joint usage of ray theory and theory of stereomechanical impact is elaborated. It is used for computer simulation of dynamical interaction of shock waves with curvilinear interfaces between anisotropic elastic media. Issues are considered which are related to the shock waves fronts surfaces bifurcations and generation of caustics connected with stress concentration and formation of zones where the stresses tend to infinity. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303697

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Two of the needed elastic parameters for predicting velocities in porous, fluid-filled rocks, the bulk modulus of the empty, porous rock and the shear modulus of the rock, are very difficult to obtain in situ. A novel modeling approach is developed by inverting the Biot-Geertsma-Gassmann (BGG) and shear-wave equations to generate values for the bulk and shear moduli, respectively, by using available velocity and porosity data obtained from borehole logs and/or cores from water/brine-saturated rocks. These values of bulk and shear moduli, along with reasonable in-situ estimates of rock-matrix and fluid parameters generated from the Batzle-Wang formulation, are then used to predict compressional and shear-wave velocities, compressional-shear wave ratios, and reflection coefficients at the interfaces between host rocks and fluid-saturated rocks, either fully or partially saturated with hydrocarbons or water, as a function of depth and/or porosity. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303698

出版商:AIP    

年代:1900

数据来源: AIP