Physical modeling and visualization of soil liquefaction under high confining stress   总被引：1，自引：0，他引：1  

Lenart González 《地震工程与工程振动(英文版)》2005,4(1):47-57

The mechanisms of seismically-induced liquefaction of granular soils under high confining stresses are still not fully understood. Evaluation of these mechanisms is generally based on extrapolation of observed behavior at shallow depths. Three centrifuge model tests were conducted at RPI‘s experimental facility to investigate the effects of confining stresses on the dynamic response of a deep horizontal deposit of saturated sand. Liquefaction was observed at high confining stresses in each of the tests. A system identification procedure was used to estimate the associated shear strain and stress time histories. These histories revealed a response marked by shear strength degradation and dilative patterns. The recorded accelerations and pore pressures were employed to generate visual animations of the models. These visualizations revealed a liquefaction front traveling downward and leading to large shear strains and isolation of upper soil layers.  相似文献   

Techniques for mode separation in Rayleigh wave testing     

Mourad Karray  Guy Lefebvre 《Soil Dynamics and Earthquake Engineering》2009

The spectral analysis of surface wave (SASW) developed in the early eighties has opened the way to the use of surface waves for the definition of shear wave velocity profiles in soil deposits or pavement structures without the need of any borings or intrusion. The SASW testing procedure was designed to minimize the contribution of higher modes and thus assumes that the Rayleigh waves which propagate at the surface belong only to the fundamental mode. Several studies have however demonstrated that, in some conditions, higher Rayleigh modes can contribute significantly to the dispersion curve. Different tests configurations exist today to deal with Rayleigh mode problem by the use of an array of receivers. In spite of that, the SASW configuration remains attractive due to the limited number of receivers, as well as, the Rayleigh modes contributing in SASW records configuration can be identified by multiple-filter technique and isolated using time-variable filters. The proposed techniques are first validated by simulated records and then applied to SASW records obtained in the field. The study confirms that higher modes can participate and even dominate in SASW records. An important contribution of higher Rayleigh modes can also exist, even if the shear wave velocity increases regularly with depth. The higher Rayleigh modes can significantly affect the accuracy of the shear wave velocity profile if they are not properly identified and separated. A multi-mode inversion process is shown to be important to have an accurate soil characterization.  相似文献   

Energy distributions of Kantowski-Sachs space-time in the theory of teleparallel gravity     

Ragab M. Gad  M. F. Mourad 《Astrophysics and Space Science》2008,314(4):341-346

We calculate the energy density and energy distribution of Kantowski-Sachs space-time, using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes, in the theory of teleparallel gravity. A comparison of the results shows that the Einstein and Bergmann-Thomson definitions furnish a consistent result for the energy density and energy distribution, but the definition of Landau-Lifshitz does not concur with them. We show that the space-time under consideration gives a counterexample that the energy distribution is the same either in general relativity or teleparallel gravity.  相似文献   

The Rupture Process and Location of the 2003 Zemmouri–Boumerdes Earthquake (Mw 6.8) Inferred from Seismic and Geodetic Data     

Rúben Santos  Bento Caldeira  Mourad Bezzeghoud  José Fernando Borges 《Pure and Applied Geophysics》2015,172(9):2421-2434

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DIRDOP: a directivity approach to determining the seismic rupture velocity vector     

Bento Caldeira  Mourad Bezzeghoud  José F. Borges 《Journal of Seismology》2010,14(3):565-600

Directivity effects are a characteristic of seismic source finiteness and are a consequence of the rupture spread in preferential directions. These effects are manifested through seismic spectral deviations as a function of the observation location. The directivity by Doppler effect method permits estimation of the directions and rupture velocities, beginning from the duration of common pulses, which are identified in waveforms or relative source time functions. The general model of directivity that supports the method presented here is a Doppler analysis based on a kinematic source model of rupture (Haskell, Bull Seismol Soc Am 54:1811–1841, 1964) and a structural medium with spherical symmetry. To evaluate its performance, we subjected the method to a series of tests with synthetic data obtained from ten typical seismic ruptures. The experimental conditions studied correspond with scenarios of simple and complex, unilaterally and bilaterally extended ruptures with different mechanisms and datasets with different levels of azimuthal coverage. The obtained results generally agree with the expected values. We also present four real case studies, applying the method to the following earthquakes: Arequipa, Peru (M _w = 8.4, June 23, 2001); Denali, AK, USA (M _w = 7.8; November 3, 2002); Zemmouri–Boumerdes, Algeria (M _w = 6.8, May 21, 2003); and Sumatra, Indonesia (M _w = 9.3, December 26, 2004). The results obtained from the dataset of the four earthquakes agreed, in general, with the values presented by other authors using different methods and data.  相似文献   

Erratum à l'article Mise en évidence et analyse d'une structure atlasique ennoyée au front de la Chaîne alpine tunisienne [C. R. Geoscience 336 (2004) 1293–1300]     

Sami Khomsi  Mourad Bédir  M. Ghazi Ben Jemia 《Comptes Rendus Geoscience》2005,337(5):547

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Preliminary results of the establishment of a marine geodetic point in the Pacific Ocean     

A. G. Mourad  J. H. Holdahl  N. A. Frazier 《Journal of Geodesy》1970,44(2):107-124

In November 1968, a marine geodetic control point was established in the Pacific Ocean at a water depth of6,200 feet. The control point (reference point) consists of three underwater acoustic transponders, two of which are powered with lead-acid batteries and the third with an underwater radioisotope power source “URIPS” with a10- to20- year life expectancy. Four independent measuring techniques (LORAC airborne line-crossing, satellite, ship inertial, and acoustic techniques) were used to measure and determine the coordinates of the control point. Preliminary analysis of the acoustic and airborne data indicates that high accuracies can be achieved in the establishment of geodetic reference points at sea. Geodetic adjustment by the method of variation of coordinates yielded a standard point error of±50 to±66 feet in determining the unknown ship station. The original location of the ship station as determined by shipboard navigation equipment was off by about1,600 feet. Paper previously published in the Proceedings of the Second Marine Geodesy Symposium of the Marine Technology Society.  相似文献   

Retention of a heavy metal by marl collected from aquifer substratum     

Mourad Bellaloui  Abdenacer Metouchi  Ahmed Foukrache  Said Larabi  Farida Semaoune 《Arabian Journal of Geosciences》2017,10(19):425

One of the objectives of this work is to characterize marl samples collected from the bedrock aquifer (at 30 m depth) of Wadi Al Ghoula located in Draria southwest of Algiers. The other objective is to make a kinetics study, linear and non-linear isotherm study, and mass transfer study of the adsorption of copper onto marl in aqueous solution. The fitness of kinetics and isotherm models was evaluated by using some error analysis function. One of the major results using an XRF technique is an evidence of the presence of calcite in the weight of 13.82%. The XRD patterns of these samples confirmed the presence of montmorillonite, kaolinite, illite, calcite, and quartz. On the other hand, the FTIR analysis clarified the presence of calcite. The specific surface area of 20,999 m²/g was obtained using the BET, which indicates that the material has a predominance for the mesoporous character. The instrumental neutron activation analysis (INAA), a nondestructive method, gives the elemental composition of the adsorbent. Based on the value of the coefficient of determination, the adsorption kinetics of copper in aqueous solution using marl as adsorbent follows the pseudo-second-order model. And according to the value of the coefficient of determination obtained for the two models, the intraparticle diffusion and liquid film diffusion control the process of adsorption of copper onto marl with low predominance for the second model of diffusion in the first stage of adsorption. The linear and the non-linear treatments of the two-parameter isotherm models (Langmuir, Freundlish, Temkin) show that the fitting best model of isotherm is the empirical Freundlish isotherm. For the three-parameter isotherm models (Toth, Sips, and Redlish-Peterson), the Sips model is the more accurate fitting model than the two other isotherms in the non-linear approach. Some error analysis functions are used to choose the best results.  相似文献