bluuebunny/crossref_metadata_2025 huggingface dataset:
Kelvin--Helmholtz instability of a horizontal interface between a finite subsonic gas and a finite magnetic liquid
Authors: Zakaria K
Published: April 2011

The nonlinear Kelvin-Helmholtz instability of a horizontal interface between a magnetic inviscid incompressible liquid and an inviscid laminar subsonic gas is investigated. The gas and the liquid are assumed to have finite thicknesses. The applied magnetic field is parallel to the solid surfaces of the considered system. The method of multiple scales is used to obtain two nonlinear Schrodinger equations describing the behaviour of the perturbed system. The stability of the progressive waves is discussed theoretically. The nonlinear cutoff wave number is obtained, where the stability conditions of the standing waves are obtained. A numerical example is applied to discuss the stability diagrams.PACS Nos.: 51.60 and 47.20
Article
Authors: Jiang D T , Crozier E D
Published: April 2011

The techniques for glancing-angle XAFS of ultrathin multilayer systems have been analyzed, with an emphasis on the conditions of detection modes under which distortion-free fine structure data are obtainable. The XANES of a multilayer system obtained in the total reflection geometry can be distorted because of anomalous dispersion effects in the sample layer and in adjacent media. The former plays a negligible role in ultrathin film cases. The latter, caused by the interference of the evanescent waves from the interfaces involved, cannot always be ignored. The distortion depends on the glancing angle, the composition of the layered structure (mainly the thickness of the layer of interest and the material of other layers), the energy from the absorption edge, and the detection modes adopted. Calculated results of these effects are presented and analytical expressions are provided in closed form. Experimental XANES data of a buried 8 monolayer (ML) Cu film, representing the thin limit, and 37 ML Ni, representing the medium thickness are used to illustrate the theory. In the thin limit, filtered fluorescence XANES data are independent of angle and are not distorted. However, total electron-yield and reflectivity data do depend on angle and are significantly distorted near the critical angle. The thickness dependence of the EXAFS measured at glancing angles is also analyzed. It is shown that both the distortions in EXAFS amplitude and phase caused by the anomalous scattering effects are strongly dependent on the sample film thickness, but when the sample thickness is in the range of 10 atomic layers the distortions are practically negligible for all X-ray incident angles. Experimental data for 8 ML bct Cu grown on Ag(001) substrate indicate that the phase and amplitude of the data have no detectable dependence on the X-ray incident angle through the critical-angle region, in agreement with the calculated results. PACS Nos. 61.10Ht, 87.64 Fb, 68.00, 68.35-p, and 68.55-a
Features of relativistic charged particles produced in catastrophic destruction of heavy emulsion nuclei at 4.5 A GeV
Authors: Singh P , Khan M S , Khushnood H
Published: April 2011

Total disintegration events produced in 4.5 A GeV/c 12C--AgBr reactions are analysed to investigate the characteristics of secondary charged particles produced in such collisions. The results reveal that multiplicity distributions of grey, black, and relativistic charged particles agree with the Poisson distribution. The average multiplicity of grey particles is found to increase with the increasing mass of projectile, while the average value of black particles is found to decrease with the increasing mass of projectile. This result is in good agreement with the prediction of fireball model. Finally, the linear dependence of grey and compound multiplicities on black, heavy, and relativistic charged particles is also observed.

PACS No.: 25.70
Self-consistent field theoryof compressible phospholipidmembranes at ambient pressure
Authors: Whitmore M D , Whitehead J P , Roberge A
Published: April 2011

We present a microscopic theory of compressible, fully hydratedphospholipid membranes in equilibrium with excess solvent, apply it toan idealized physical model of these systems, and calculate a broadrange of their thermodynamic and structural properties. An essentialfeature of the theory is the anisotropy of the effective fields actingon each of the hydrocarbon segments, which arises as a naturalconsequence of the hard-core repulsions between segments and theconnectivity of the lipid molecules. These fields, along with theinhomogeneous particle and bond density distributions throughout thebilayer interior, are determined via numerical, self-consistent fieldcalculations. In addition to the gel and liquid crystal phases, themodel naturally includes the fully intercalated LβI phase. Theincorporation of compressibility effects enables us to calculatevarious effects of pressure and the density change at the transitionand in the liquid crystal phase. In this paper, we focus on theproperties of fully hydrated (DPPE) in the liquid crystal phase,as well as properties of the main transition, at atmosphericpressure. To a lesser extent, we also discuss predicted dependencesof several key properties on chain length and head group size. Despiteits simplifications, the model provides a quantitative description ofmany of the measured properties of DPPE, and the correct qualitativetrends for the other lipids. In an accompanying paper [the following article], we examine the effects ofpressure, and obtain quantitative agreement with recent observations onoverall density and bilayer thickness.PACS Nos.: 87.22.Bt, 87.10.+e, 64.60.Cn
Heavy-ion storage ring measurement of forbidden transition rates between ground-configuration levels in Si6+ and Si8+ ions
Authors: Träbert E , Wolf A , Pinnington E H , Linkemann J , Knystautas E J , Curtis A , Bhattacharya N , Berry H G
Published: April 2011

The decay by magnetic dipole and electric quadrupole (M1 and E2) transitions of the 2s22p2 1D2 level in the ground complex of the C-like ion Si8+ and the 2s22p4 1D2 level in the O-like ion Si6+ have been optically observed with ions circulating in a storage ring. The measured natural level lifetimes of (38.3 ± 0.3) ms for Si8+ and (636 ± 0.7) ms for Si6+ corroborate theoretical data for such forbidden decays in multicharged ions of astrophysical interest. PACS Nos.: 32.70.Cs, 32.30.Jc, 34.50.Fa
Article
Authors: Takashima M
Published: April 2011

The stability of combined plane Poiseuille and Couette flow of an electricallyconducting fluid under a transverse magnetic field is investigated using linear stability theory.In deriving the equations governing the stability, the so-called magnetic Stokes approximationis made using the fact that the magnetic Prandtl number Prm for most electrically conductingfluids is extremely small. The Chebyshev collocation method is adopted to obtain theeigenvalue equation, which is then solved numerically. The critical Reynolds number Rec,the critical wave number αc, and the critical wave speed cc are obtained for wide ranges ofthe Hartmann number Ha and the parameter k = U0 / (U0 + nu0), where U0 is the maximumvelocity of pure Couette flow and nu0 is the maximum velocity of pure Poiseuille flow. It isfound that a transverse magnetic field has both stabilizing and destabilizing effects on theflow depending on the value of k.PACS Nos. 47.20
Massive-scalar effective actions on anti-de Sitter space-time
Authors: Kamela M , Burgess C P
Published: April 2011

Closed forms are derived for the effective actions for free, massive spinless fields in anti-de Sitter space-times in arbitrary dimensions. The results have simple expressions in terms of elementary functions (for odd dimensions) or multiple Gamma functions (for even dimensions). We use these to argue against the quantum validity of Cruz' recently proposed duality relating such theories with differing masses and cosmological constants.PACS Nos. 11.10- z, 11.90+ t, and 04.60-m.
Article
Authors: Kedzierski W , Brennan M , McConkey J W
Published: April 2011

A variety of techniques have been applied to study the interaction of electrons with beams of CO2 molecules which are heavily clustered. Fragmentation of the clusters is monitored by detecting excited fragments directly or via the vacuum ultra-violet photons which they emit as they decay. The evidence obtained points to the conclusion that the excited molecules are essentially decoupled from the clusters during fragmentation. The shape of the excitation functions are indicative of the dominance of optically allowed processes in the initial interaction.PACS Nos.: 36.40+d and 34.80.GS
Vibrational modes of a rotating string
Authors: Allen T J , Schmidt J R
Published: April 2011

Motivated by nonrelativistic models of a QCD (quantum chromodynamic) string, we examine the systemof a nonrelativistic string in uniform rotational motion with one endfixed and with a mass (quark) attached to the other end. A QCD string hasno purely longitudinal modes, so some constraint must be imposed upon thenonrelativistic system to exclude these modes. Accordingly, we examinethe cases that the string is either inextensible or purely transverse. Foreach case we solve first the discretized string and then do the continuumcase. We find the small amplitude oscillatory motions and frequencies ofoscillation of the string and mass. We show that the assumption of a nodeat the end of the inextensible string produces frequencies that are veryclose to the actual frequencies. For the transverse string, we show thatkeeping centrifugal terms for the motion of the masses comprising thestring leads to an unstable mode.PACS Nos.: 03.20.+i, 03.40.-t, 12.39.Mk
Resonant fluorescence spectra of a multilevel system in intense radiation and external magnetic fields
Authors: Karagodova T Ya.
Published: April 2011

Theory and methods of computer simulations permit investigation of the interaction of high-power laser radiation, up to GW/cm2, with atoms having both small and large fine-structure intervals compared with interactions with a laser field and an external magnetic field. The modifications of the energies and population of atomic levels due to such interactions lead to nonlinear effects. Besides modifications in the Raman effect and new effects of rotation of the plane of polarization and circular dichroism that were investigated earlier, there are such nonlinear effects as the modification of the number, positions, intensities, and polarizations of the lines in the resonant fluorescence spectrum. Numerical experiments permit investigation of the characteristics of resonant fluorescence and comparison with known experimental results.PACS Nos.: 32.50, 78.20.L, 42.65, 42.50.H
Relativistic high-order harmonics of a hydrogenlike atom in an ultrastrong laser field
Authors: Chen J , Li K H , Wen J H
Published: April 2011

The relativistic high-order harmonics of a hydrogenlike atom in an ultrastrong laser field has been simulated by the classical Monte-Carlo method in this paper. The results concerning the influence of the laser parameters (frequency, pulse-shape, intensity, etc.) on the relativistic high-order harmonics have been obtained and the conversion efficiency has also been calculated. Some conclusions are drawn and discussed.PACS Nos.: 42.65Ky and 32.80Rm
Duality and color confinement in restricted gauge theory
Authors: Rana JMS
Published: April 2011

Using electromagnetic duality, the isocolor charge-dyon interactions were studied in restricted quantum chromodynamics (RCD) in terms of current-current correlations in the magnetic gauge using the dielectric and permeability parameters of the associated vacuum. The resulting 1/k4 behaviour of the dual propagators is interpreted as a signature of confinement for the corresponding colored fluxes of the theory. Evaluating the vortex solutions of RCD semi-quantitatively, in accordance with Higgs-Ginzburg-Landau theory, expressions for London penetration depth, coherence length, and associated flux energy functions for types I and II superconducting media are derived and an analogy of the type of superconducting medium with the bag model and string picture of hadrons is discussed.PACS Nos.: 11.30 Jw, 14.80 Hv, 12.38 Aw
Structural and magnetic properties of nitrided finemet-type ribbons
Authors: Atmani H , Grognet S , Teillet J , Zellama K , Zuberek R
Published: April 2011

Nitriding thermochemical treatment under suitable parameters is used to nano-crystallize Fe73.5Cu1Nb3Si13.5B9 ribbon. This new kind of treatment leads to finer nano-structure and modifies the structural parameters of the α-Fe(Si) phase, obtained during the treatment. The magnetic properties are also improved; specific magnetization at room temperature and Curie temperature of the crystalline phase increase, and the magnetostriction constant becomes smaller. The nitrogenation seems to offer a new way to obtain nanostructured ribbons. PACS No.: 75.70
High-temperature corrections for the classical expressions of radiative losses from a black body
Authors: Sisman A
Published: April 2011

The contribution from thermally generated electron-positron pairs to the radiative losses from a black body is considered near the temperature corresponding to the electron's rest mass energy Tc = mec2/k. The correction factors are defined as the ratio of corrected expressions (which also include the contribution from thermal pairs) to the classical expressions (which include merely photons). The correction factors for energy, free energy, and entropy fluxes have different values about 0.5Tc, while they have the same value at T « Tc and T » Tc. The Stephan-Boltzmann's constant becomes temperature dependent due to the contribution of thermal pairs. According to the classical expressions of radiative losses, the ratio of energy flux to the absolute value of free energy flux is a constant and it is equal to 3. On the contrary, it is shown that it is a function of temperature about Tc and it has a maximum about 0.38Tc. The correction factor for mean energy per emitted thermal particle has also a maximum about T = 0.42Tc. PACS No.: 4440
A problem of a micropolar magnetohydrodynamic boundary-layer flow
Authors: Ezzat M A , Othman M I , Helmy K A
Published: April 2011

The matrix exponential method, which constitutes the basis of the state space approach of modern control theory, is applied to the nondimensional equations of unsteady boundary layer flow past an infinite plane surface with a pressure gradient. Laplace-transform techniques are used. The results obtained can be used to generate solutions in the Laplace-transform domain to a broad class of problems in magneto-hydrodynamic boundary layer flow. The technique is applied to the problem of an electrically conducting micropolar fluid flowing past a vertical plane surface in the presence of a transverse magnetic field and to the problem of flow between two parallel plates. A numerical method is employed for the inversion of the Laplace-transforms. Numerical results are given and illustrated graphically for both problems.PACS No.: 47.65+a
Plane wave diffraction by two parallel overlapped thick semiinfinite impedance plates
Authors: Birbir F , Büyükaksoy A
Published: April 2011

A new approach consisting of employing the mode matching method inconjunction with the Fourier transform technique is used to analyse thediffraction of time harmonic plane waves by two parallel overlapped thickimpedance half-planes. The problem is formulated as a pair of uncoupledmodified Wiener-Hopf equations and solved approximately. Numerical resultsillustrating the effects of various parameters such as wall thickness, plateto plate separation distance, wall impedance, etc. on the diffractionphenomenon are presented.PACS No.: 41.20jb
Dissipative quantum evolution of a spin system in a magnetic field
Authors: Wolf C
Published: April 2011

By allowing for dissipative interaction between a quantum spin system and the environment we calculate the frequencies and decay rates of the components of the x spin polarization for a spin system precessing in a magnetic field when the spin system has dimensionality corresponding to S= ½,1,3/2 .PACS. No.: 03.65
Atomic interface structure-property investigations
Authors: Kavanagh Karen L
Published: April 2011

Our current understanding of the relationship between interfacial structure and the resulting properties remains very rudimentary.This is a concern for many fields and applications, includingmetal/semiconductor contacts, insulator/semiconductor field effect junctions, magnetic multilayers, ferroelectric thin films, and semiconductor heterostructures. The situation is slightly improved in the case of epitaxial growth where a deposited layer follows the structure of the underlying substrate. However, even with these systems the interfacial properties are difficult to predict accurately, even when impurities and defects can be ignored. This paper highlights a number of recent examples of interface structure-property investigations that have attempted to understand how the interface formation determines the relevant film or interface property.PACS Nos.: 68.55.Jk, 68.55.Ln, 68.65.+g
Hydraulic conductivity of kaolinite-silt mixtures subjected to closed-system freezing and thaw consolidation
Authors: Konrad Jean-Marie , Samson Martin
Published: April 2011

Kaolinite-silt mixtures at different clay contents were subjected to closed-system freezing and thaw consolidation to obtain data on the hydraulic conductivity of thawed samples. A simplified void ratio model was developed based on the compressibility characteristics of the clay aggregates and the freezing-induced suctions. The close agreement between predictions and observations suggests that the assumptions of the model are reasonable, especially that maximum freezing-induced suctions developed in the clay aggregates are related to the temperature at which no significant change in unfrozen water content occurs rather than the actual freezing temperature. Furthermore, the compression characteristics of thawed mixtures is essentially controlled by the recompression of the clay aggregates in the overconsolidated domain. The void ratio model is linked to a permeability model that suggests that the hydraulic conductivity of thawed mixtures can be defined by a reference value of the unfrozen soil and a parameter specific to each mixture.Key words: freeze-thaw, laboratory, hydraulic conductivity, conceptual model, silt, kaolin.
An unusually large debris flow at Hummingbird Creek, Mara Lake, British Columbia
Authors: Jakob M , Anderson D , Fuller T , Hungr O , Ayotte D
Published: April 2011

On 11 July 1997 a very large debris flow occurred at Hummingbird Creek, Mara Lake, British Columbia. Long-term antecedent precipitation was record breaking, whereas short-term precipitation at Salmon Arm did not exceed the 2 year return period for intensity. A 25 000 m3 debris avalanche was initiated downstream of a forest road culvert, which drained a small catchment that had been artificially increased by a factor of three. The debris avalanche entered the channel of Hummingbird Creek and triggered a debris flow. Velocities were back-calculated using the forced vortex equation and multiplied by the cross-sectional area to obtain peak discharge estimates that ranged from 600 to 1000 m3/s. Approximately 92 000 m3 of sediment was deposited during this event, which makes it the largest nonvolcanic debris flow recorded in British Columbia to date. A three-dimensional runout model was used to simulate this event. Results are in fair agreement with the observed behaviour. This study emphasizes the need to carefully manage forest resources with high downstream risks and the need for hazard assessments prior to development on alluvial fans.Key words: debris avalanche, debris flow, DAN model, hydroclimatic, peak discharge, British Columbia.
Modélisation numérique des mouvements de terrain meuble induits par un tunnelier
Authors: Benmebarek S , Kastner R
Published: April 2011

The construction of shallow tunnels causes movements that can affect existing structures, inducing unacceptable disorders. These disorders can not only result from settlements but also from horizontal displacements. In the case of tunneling with pressurized face shield boring machines, ground movements are found to be the result of complex interactions between soil, construction stages, and shield drive parameters. In this context, the direct prediction of final ground movements by empirical, or analytical, and numerical approaches has proven to be insufficient. It is therefore necessary to develop and to validate more accurate simulation tools to allow assessment of the magnitude and distribution of soil movements in relation to construction stages. By experimental results of two sections of the Lyons D line subway extension (1993-1995), the authors examine various numerical procedures, in this paper. A two-dimensional procedure, taking into consideration various stages of construction, is proposed. The confrontation of this approach to experimental results shows the necessity of corrections due to three-dimensional effects of various tunneling stages.Key words: tunnels, shield, settlement, monitoring, grout, numerical modeling, back-analysis.
Three-dimensional finite element analyses of embedded retaining walls supported by discontinuous earth berms
Authors: Gourvenec Susan M , Powrie William
Published: April 2011

A series of three-dimensional finite element analyses has been carried out to investigate the effect of the removal of sections of an earth berm supporting an embedded retaining wall. For the particular wall-berm geometry and ground conditions considered in these analyses, relationships between the wall movement, the length of berm section removed, the spacing between successive unsupported sections, and the time elapsed following excavation are presented and discussed. The analyses show that, for a given elapsed time, wall movements are proportional to the length of the excavated berm section provided that the unsupported sections are sufficiently widely spaced. If the spacing between unsupported sections is reduced below some critical value, wall movements then depend on both the length of and distance between the excavated berm sections.Key words: finite element analyses, diaphragm walls, earth berms, construction sequence, three-dimensional effects.
CANLEX full-scale experiment and modelling
Authors: Byrne P M , Puebla H , Chan D H , Soroush A , Morgenstern N R , Cathro D C , Gu W H , Phillips R , Robertson P K , Hofmann B A , (Fear) Wride C E , Sego D C , Plewes H D , List B R , Tan S
Published: April 2011

A major aim of the Canadian Liquefaction Experiment (CANLEX) was to verify analysis procedures for predicting liquefaction phenomena. Towards this purpose, two loading events were carried out: a field event comprising a clay embankment built over a loose sand foundation layer, and a centrifuge test performed on a model of a sand embankment structure. Both the field event and the centrifuge model were planned so as to induce a static liquefaction failure and were instrumented to observe their response in terms of displacement and pore pressure. The fundamental mechanical characteristics of the foundation layer were determined from laboratory element tests (triaxial and simple shear). These tests formed the basis for the stress-strain modelling used in the numerical analyses. Two fundamentally different modelling techniques were used. One involved a fully coupled plasticity model, and the other involved a model based on a collapse-surface approach. The model and prototype structures were then analyzed and the predicted results in terms of displacements and pore pressures were compared with the measured values. The results from both approaches were found to be in reasonable agreement with the measurements, provided allowance was made for direction of loading and drainage effects were accounted for.Key words: liquefaction, field experiment, embankment, centrifuge model, elastic-plastic model.
Characterization of a smear zone around vertical drains by large-scale laboratory tests
Authors: Sharma J S , Xiao D
Published: April 2011

Installation of prefabricated vertical drains using a mandrel causes disturbance of clay surrounding the drain, resulting in a "smear" zone of reduced permeability. In this paper, an attempt is made to characterize the smear zone using large-scale laboratory model tests. Two tests, simulating the cases of "no smear" and "with smear," were conducted. Excess pore-water pressures were monitored at seven different locations along the radial direction. In addition, undisturbed samples were collected at various locations in the clay layer for conducting oedometer tests. The distribution of excess pore pressure due to drain installation gave a clear indication of the extent of the smear zone. The effect of reconsolidation on the properties of clay was found to be much greater than that of the remoulding of the clay. The extent of the smear zone was also confirmed from the change in permeability of the clay layer in the smear zone obtained from oedometer tests. The radius of the smear zone is about four times that of the mandrel, and the horizontal permeability of the clay layer in the smear zone is approximately 1.3 times smaller than that in the intact zone.Key words: consolidation, permeability, smear zone, soft clay, vertical drains.
Dynamic analysis for laterally loaded piles and dynamicp-ycurves
Authors: Naggar M Hesham El , Bentley Kevin J
Published: April 2011

Pile foundations are often subjected to lateral dynamic loading due to forces on the supported structure. In this study, a simple two-dimensional analysis was developed to accurately model the pile response to dynamic loads. The proposed model incorporates the static p-y curve approach (where p is the static soil reaction and y is the pile deflection) and the plane strain assumptions to represent the soil reactions within the frame of a Winkler model. The p-y curves are used to relate pile deflections to the nonlinear soil reactions. Wave propagation and energy dissipation are also accounted for along with discontinuity conditions at the pile-soil interface. The inclusion of damping with the static unit transfer curves results in increased soil resistance, thus producing "dynamic p-y curves." The dynamic p-y curves are a function of the static p-y curve and velocity of the soil particles at a given depth and frequency of loading. The proposed model was used to analyze the pile response to the lateral Statnamic load test, and the predicted response compared well with the measured response. Closed-form solutions for dynamic p-y curves were established by curve fitting the dynamic soil reactions for a range of soil types and loading frequencies. These solutions can be used to model soil reactions for pile vibration problems in readily available finite element analysis (FEA) and dynamic structural analysis packages. A simple spring and dashpot model was also proposed to be used in equivalent linear analyses of transient pile response. The proposed models were incorporated into an FEA program (ANSYS) which was used to compute the response of a laterally loaded pile. The computed responses compared well with the predictions of the two-dimensional analysis.Key words: dynamic, transient, lateral, piles, p-y curves, inertial interaction.
Parameter determination for nonlinear stress criteria using a simple regression tool
Authors: Li Li , Gamache Michel , Aubertin Michel
Published: April 2011

In geotechnique, laboratory test results are often employed to estimate the parameter values required for the application of criteria commonly used to define specific stress states such as yielding, failure, and residual strength. Many of these criteria rely on a nonlinear formulation relating the different stress tensor components (or the corresponding invariants). There are many regression techniques that can be selected to obtain corresponding parameters based on experimental results. Some of these can be fairly complex but, considering the intrinsic variability of the available data on geomaterials, relatively simple methods are usually deemed sufficient. In that regard, one should favor methods directly available from common software packages. In this paper, the authors present a simple analysis procedure based on Microsoft Excel®which can be applied to different two- and three-dimensional stress criteria. As an example, the technique is applied to the failure strength of rock samples using two nonlinear criteria.Key words: rock mechanics, failure criterion, curve fitting, regression analyses, parameter determination.
The effect of temperature on adsorption of organic compounds to soils
Authors: Sleep Brent E , McClure Paul D
Published: April 2011

Column experiments were performed at 2225°, 50°, and 92°C to study the effect of temperature on the sorption of toluene, perchloroethylene, and naphthalene to a silty gravel-till aquifer material. A one-dimensional numerical model incorporating kinetic adsorption with gamma-distributed rate constants was developed and fit to the data. As temperature was increased from 2225° to 90°C, sorption coefficients decreased by 35, 40, and 60% for toluene, perchloroethylene, and naphthalene, respectively. The means and variances of the gamma distributions for sorption rate constants both increased as temperature increased. The increases in variance were attributed to the short contact times of the experiments and the increased sorption rates at higher temperatures. The decreases in sorption coefficients and increases in sorption rate constants as temperature is increased suggest that thermal remediation techniques such as hot-water and steam flushing may accelerate the removal of sorbed organic soil contamination.Key words: sorption, nonequilibrium, temperature dependence, thermal remediation.
Earthquake-induced deformation analyses of the Upper San Fernando Dam under the 1971 San Fernando Earthquake
Authors: Wu Guoxi
Published: April 2011

A nonlinear effective stress finite element approach for dynamic analysis of soil structure is described in the paper. Major features of this approach include the use of a third parameter in the two-parameter hyperbolic stress-strain model, a modified expression for unloadingreloading modulus in the MartinFinnSeed pore-water pressure model, and an additional pore-water pressure model based on cyclic shear stress. The additional pore-water pressure model uses the equivalent number of uniform cyclic shear stresses for the assessment of pore-water pressure. Dynamic analyses were then conducted to simulate the seismically induced soil liquefaction and ground deformation of the Upper San Fernando Dam under the 1971 San Fernando Earthquake. The analyses were conducted using the finite element computer program VERSAT. The computed zones of liquefaction and deformation are compared with the measured response and with results obtained by others.Key words: effective stress method, finite element analysis, Upper San Fernando Dam, earthquake deformation, VERSAT.
Static response of fly ash columnar improved ground
Authors: Porbaha A , Pradhan T BS , Kishida T
Published: April 2011

This study presents the results of a series of monotonic undrained triaxial compression tests on clay specimens improved by columnar reinforcement. The process of loading and stress redistribution of a fly ash  clay specimen (FCS), in comparison with a sandclay specimen (SCS), is examined in terms of stressstrain characteristics, generation of excess pore-water pressure, effective and total earth pressures, development of stress concentration, and the normalized undrained shear strength of the improved soil. It was found, predictably, that the deviator stress of the composite specimens was influenced by the consolidation stress, replacement area ratio, and properties of the column material. The stress concentration at the top of the composite ground which depends on the loading stage reaches a peak after the consolidation state and is reduced due to stress redistribution between the column and the soft ground. In terms of improvement effects, the mean shear strengths of FCS and SCS relative to the clay specimen are three and seven times greater, respectively, for a replacement area ratio of 49%.Key words: composite ground, fly ash, soil improvement, soft ground, triaxial test.
Axial compressive capacity of driven piles in sand: a method including post-driving residual stresses
Authors: Alawneh Ahmed Shlash , Nusier Osama , Husein Malkawi Abdullah I , Al-Kateeb Mustafa
Published: April 2011

In this paper, empirical formulae were developed between the well-known pile bearing capacity factors (Nqand β) and parameters which include friction angle of sand, relative density, average effective vertical stress, and deformability of the soil below the pile toe. The developed empirical formulae were totally based on a database comprised of 28 well-documented compressive pile load tests collected exclusively from geotechnical literature. The actual measurements of shaft and end-bearing resistances of each pile in the database were adjusted to account for post-driving residual loads. Calculation of pile bearing capacity factors (Nqand β) was based on the adjusted shaft and end-bearing resistances rather than the actual unadjusted measured resistances for residual loads. Comparison of predicted and measured compressive capacity of an independent database comprised of 18 pile load tests showed that the developed formulae yield a reasonably accurate estimate of compressive pile capacity in cohesionless soils.Key words: driven piles, residual load, toe resistance, shaft resistance.
Stress distributions and paths in clays during pressuremeter tests
Authors: Silvestri V , Diab R
Published: April 2011

This paper presents a novel analysis for the interpretation of pressuremeter tests in clay. No prior knowledge of the constitutive properties of the material is required. Shear, radial, and tangential stresses are determined at various distances from the probe and for different levels of cavity strain. Total and effective stress paths followed by material elements within the deformed soil are represented on shear stress  normal stress diagrams. The analysis is applied to the interpretation of pressuremeter tests carried out in both the field and the laboratory.Key words: pressuremeter tests, clays, novel analysis, stressstrain curves, stress distributions, stress paths.
Seismic passive earth pressure coefficients for sands
Authors: Kumar Jyant
Published: April 2011

By taking the failure surface as a combination of the arc of a logarithmic spiral and a straight line, passive earth pressure coefficients in the presence of horizontal pseudostatic earthquake body forces have been computed for an inclined wall placed against cohesionless backfill material. The presence of seismic forces induces a considerable reduction in the passive earth resistance. The reduction increases with an increase in the magnitude of the earthquake acceleration. The effect becomes more predominant for loose sands. The obtained results compared well with those reported in the literature using curved failure surfaces. However, the results available in the literature on the basis of a planar failure surface are found to predict comparatively higher passive resistance.Key words: earth pressures, earthquakes, limit equilibrium, plasticity, retaining walls, sands.
Soil behavior during freezing and thawing using variable and constant confining pressure triaxial tests
Authors: Simonsen Erik , Isacsson Ulf
Published: April 2011

Although variable confining pressure (VCP) triaxial tests are generally preferred to constant confining pressure (CCP) triaxial tests due to the more realistic stress application, VCP tests have never been utilized when investigating freezethaw effects on unbound road materials. In this study, three soils were investigated for resilient behavior during freezing and thawing utilizing both VCP and CCP triaxial testing. The soils were tested at selected temperatures between +20 and 10°C during one full freezethaw cycle. The results were analyzed in terms of the traditionally used resilient modulus and Poisson's ratio, as well as volumetric and shear components, and indicate a significant difference in moduli computed from CCP and VCP data. However, resilient moduli display compatible values when interpreted in terms of mean values of deviator stress and mean normal stress. With regard to freezevthaw effects on resilient moduli, the results are inconsistent with previous findings. However, this can be explained by the different test conditions applied.Key words: freezethaw, triaxial tests, unbound pavement materials, subgrade soils, resilient modulus.
Coefficient of consolidation from the linear segment of the t1/2 curve
Authors: Feng Tao-Wei , Lee Yi-Jiuan
Published: April 2011

The coefficient of consolidation is commonly determined by fitting the Terzaghi theoretical time factor, T, versus average degree of consolidation, U, relationship to the measured oedometer consolidation curve. A simplified version of the Taylor t1/2 method is proposed in this paper. Since the theoretical T1/2 versus U relationship is linear up to 60% consolidation, the measured t1/2 consolidation curve may also present a linear segment that ends at 60% consolidation. Samples of 10 natural soft clays with liquid limits ranging from 40 to 152% were used to carry out conventional oedometer tests with consolidation increments in the recompression range, spanning the preconsolidation pressure, and in the compression range. Based on the oedometer test results, the effects of secondary compression on the shape of the t1/2 consolidation curve are evaluated and found limited between 60% and 90% consolidation. In the proposed simplified t1/2 method, the time of 60% consolidation is recognized from the lower end of the linear segment and is used together with the Terzaghi theoretical time factor of 0.286 and the maximum drainage distance of the oedometer specimen to determine the coefficient of consolidation. A large amount of the oedometer coefficient of consolidation data obtained from the simplified t1/2 method are in good agreement with those from the Taylor t1/2 method and are within one to two times those from the Casagrande logarithm of t method.Key words: laboratory tests, coefficient of consolidation, curve fitting method, settlement.
One- and two-dimensional seismic analysis of solid-waste landfills
Authors: Rathje Ellen M , Bray Jonathan D
Published: April 2011

The results from one-dimensional (1D) and two-dimensional (2D) dynamic response analyses are compared to determine the reliability of the common practice of using 1D analysis to evaluate the seismic response of solid-waste landfills. Results indicate that 1D analysis generally provides a reasonably conservative estimate of the seismic loading and earthquake-induced permanent displacement for deep sliding surfaces, such as along the base liner. However, caution is warranted for shallower sliding surfaces, where 2D topographic amplification often results in larger values of seismic loading and permanent displacement than that predicted by 1D analysis. The 1D2D analysis comparison is not just a function of geometry, but is also dependent on the different numerical formulations typically employed in each procedure (e.g., 1D wave propagation versus 2D finite element). Comparisons of accelerations along the landfill surface indicate that 1D analysis consistently under predicts the maximum horizontal acceleration (MHA) along the slope near the crest of the landfill. However, the seismic loading is shown to vary systematically with normalized cover slope length, with the maximum equivalent acceleration for the full cover slope being about 40% of the peak acceleration at the crest. Based on the results of this study, a simplified procedure is proposed for scaling 1D results to account for 2D topographic amplification and cover slope averaging when evaluating the seismic performance of landfill cover systems.Key words: solid-waste landfill, dynamic response, seismic loading, finite element analysis, Newmark sliding block analysis, damping.
Computer tomographic analysis of undisturbed samples of loose sands
Authors: Pralle Norbert , Bahner Malte L , Benkler Josef
Published: April 2011

Spontaneous flows of very loose sand deposits pose a serious environmental problem in abandoned lignite mines. Large areas in eastern Germany are not safe for public access. Slight disturbances have triggered large settlement flows, causing loss of lives and structures. To better understand the mechanisms of fast settlement flows, undisturbed samples from depths between 10 and 15 m below ground level were retrieved using the soil-freezing method. Conventional laboratory and computer tomographic soil analyses were performed on these samples. The results reveal a very low degree of saturation and large gas-filled macropores responsible for considerable density fluctuations within the phreatic zone. These spatial porosity variations are thought to strongly contribute to the collapsibility of loose sands.Key words: spontaneous liquefaction, undisturbed sampling, soil freezing, computer tomography, density fluctuations, gas inclusions.
Effect of zeolitization on physicochemico-mineralogical and geotechnical properties of lagoon ash
Authors: Kolay P K , Singh D N
Published: April 2011

A common method to dispose of ash generated from coal-fired thermal power plants is to mix the ash with water and place the ashwater slurry in ponds or lagoons. Such a disposal system allows for the ashwater interaction. Alkalis present in the ash react with water, leading to zeolitization of the ash and changes in its overall properties. To simulate such interaction, controlled experiments have been conducted on a typical Indian lagoon ash, and the effect of zeolitization on the physicochemicomineralogical properties has been studied. The effect of zeolitization on the geotechnical properties of the ash has also been investigated in detail. It is believed that such investigations are essential for bulk utilization of the lagoon ash, particularly as a fill material, where properties like compaction, consolidation, and hydraulic conductivity are very important.Key words: lagoon ash, physical properties, chemical composition, mineralogy, geotechnical characteristics, zeolitization.
Some Factors Controlling the Predictability of Stress-Strain Behaviour of Clay
Authors: Ladanyi B , LaRochelle P , Tanguay L
Published: April 2011

A graphical interpolation method which had previously been used for predicting the behaviour of sand in triaxial test conditions has been modified to become applicable to a remoulded saturated clay.The method consists in covering a given region of the principal stress plane by the results of a number of drained compression tests whose stress paths are related to a common consolidation line and are sufficiently close to each other so as to enable intermediate values of different parameters to be found by simple interpolation.The method was applied to a remoulded saturated clay both in normally consolidated and overconsolidated state, and an attempt was made to predict by interpolation the behaviour of the clay in undrained shear and K0-consolidation test respectively.By comparing the predicted behaviour of the clay with that observed in actual tests, a fair agreement was found for undrained tests, whereas for the K0-consolidation test the agreement was poor.It is suggested that the predicting of the behaviour of the clay in a given type of test on the basis of a general picture obtained from a series of tests of a different type is possible provided that in both types of tests the type of consolidation, the sign of the isotropic and deviatoric components of the strain tensor, and the rate of strain are respectively the same.
Correlating Freeze-Up and Break-Up with Weather Conditions
Authors: Williams G P
Published: April 2011

The results of studies on the relation between freeze-up, break-up and weather conditions for a small fresh-water lake in the Ottawa area are reported. Techniques using air temperature records for estimating when a solid ice-cover will form on the lake are investigated. .A formula using weather records is also developed for estimating the time taken for ice to melt from the lake. The usefulness of these relationships for estimating “freeze-up” and “break-up” dates for rivers and lakes is discussed.
Clay Layer Fabric and Oedometer Consolidation of a Soft Varved Clay
Authors: Quigley R. M. , Ogunbadejo T. A.
Published: April 2011

The oedometer consolidation properties of the clay layers of varved sediments from New Liskeard, Ontario have been presented and interpreted with reference to current ideas on soil fabric, bonding, and environment of deposition. The sensitive, brittle nature of the clays is expressed by Cc values as high as 1.35 and "S" shaped consolidation curves. Preconsolidation above any previous possible overburden pressure is explained by bonding of a net random, flocculated fabric as measured by X-ray diffraction methods. Rates of secondary consolidation up to 4.5%/log cycle at loads close to the preconsolidation pressure reflect structural breakdown of the soil fabric within a very critical range of stress and strain.The flocculated soil structure at New Liskeard is compared with the more parallel fabric of the compositionally similar stratified glacial clays at Welland, Ontario. It is suggested that both deposits developed flocculated soil structures during deposition but that the Welland clays were deposited and loaded more rapidly so that time dependent bonding could not develop to resist compression and retain the open structure as at New Liskeard and most other slowly deposited varved clays in eastern Canada. A literature review is presented in support of these ideas.
Performance of a 48-in. Warm-oil Pipeline Supported on Permafrost
Authors: Rowley R. K. , Watson G. H. , Wilson T. M. , Auld R. G.
Published: April 2011

An experimental pipeline loop, 2000 ft (609.8 m) long and 4 ft (1.22 m) in diameter, was constructed on the Mackenzie Valley Pipe Line Research Limited test site near Inuvik, N.W.T. Oil at 160 °F (71 °C) was circulated through the loop from February 1971 until January 1972 and performance of the continuous gravel berm and intermittent pile bent support systems and ice-rich permafrost foundation monitored.Instrumentation was placed on and around the pipeline to measure settlement and temperature. Site climatological data were also compiled. Settlement and other movements were monitored by periodically taking elevations at the ground surface and on survey rods attached directly to the pipe. Temperatures were measured using both resistance thermal device (R.T.D.) and thermistor type sensing elements. Measured changes in the foundation soil thermal regime were compared with performance as predicted by a two-dimensional thermal simulator model.The observed pipeline loop performance is discussed and compared with predictions for both foundation thawing and settlement. Applicability of the thermal simulator model used and the support piling behavior is also discussed.
Concrete to Bedrock Bond Testing by Jacking from Bottom of a Bore Hole
Authors: Gibson G. L. , Devenny D. W.
Published: April 2011

A low cost in situ method of testing the bond between concrete and bedrock is described. The test can be performed in exploration bore holes as part of a detailed site investigation.A hydraulic jack is placed at the bottom of a specially prepared bore hole and a concrete plug cast above it. After the concrete has cured, pressure is applied to the jack until the concrete plug slips. Bond stress is computed by dividing the applied load by the peripheral area of the plug.The test provides realistic bond values for the design of rock sockets as well as useful information for the bidding contractors.