bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption intensity measurements of the second overtone band of NO
Authors: Chandraiah G. , Gillard P.
Published: April 2011

The absolute intensity A3–0 of the second overtone band of NO has been measured using helium and argon as pressure broadening gases at mixture densities up to 360 amagat. The absolute intensity, obtained from the integrated absorption coefficients of NO–He and NO–Ar gaseous mixtures at high pressures, is found to be (4.08 ± 0.21) × 10−2 cm−2 amagat−1. From the line intensity measurement data of Meyer, Haeusler, and Barchewitz and the absolute intensity obtained with the NO–He gaseous mixtures, the rotationless matrix element R3–0 (0) of the 3–0 band of NO is calculated and its value is 7.75 × 10−4 D. This value of R3–0 (0) is combined with previous results on the NO 1-0 and 2-0 bands to obtain a dipole moment expression accurate to M3. The following expansion for the dipole moment function in the ground state of NO is determined: M (x) = −0.166 + 2.56x−1.94x−1.20x3 D, where x is the relative internuclear separation (r−re)/re.
Propagation d'un élément de matrice K nucléaire dans un potentiel coulombien écranté
Authors: Lagrange Ch.
Published: April 2011

We investigate at low energies propagation methods of a nuclear K matrix element through a screened Coulomb potential. From thermal energies up to a few kiloelectronvolts, the method we have adopted allows us to handle the numerical evaluation of atomic and nuclear collisions at low energies with great confidence.
Gravité quantique et modèles de matrices
Authors: Sénéchal David
Published: April 2011

A review of the main results recently obtained in the study of two-dimensional quantum gravity is offered. The analysis of two-dimensional quantum gravity by the methods of conformal field theory is briefly described. Then the treatment of quantum gravity in terms of matrix models is explained, including the notions of continuum limit, planar approximation, and orthogonal polynomials. Correlation fonctions are also treated, as well as phases of the matrix models.
Coherent-state path integral operator ordering, and regularization: A simple example
Authors: Voon Lok C. Lew Yan
Published: April 2011

For a restricted class of potential problems, the Feynman path integral in the coordinate representation circumvents operator-ordering ambiguities. We will show that, in the coherent-state representation, the traditional continuum time path integral cannot resolve this issue. Using a simple solvable model, we carry out a careful analysis of the continuum limit with regularization. The latter is found to be necessary to address the operator-ordering issue.
A study of pre-equilibrium emission in α-induced reactions on 121,123Sb
Authors: Singh B. P. , Bhardwaj H. D. , Prasad R.
Published: April 2011

Excitation functions for the 121Sb (α, n)+ 123Sb(α, 3n),,21Sb(α, 2n)+ 123Sb(α, 4n), 121Sb(α, 4n), 121Sb(α, 3np), and 123Sb(α, n) reactions are measured in the energy range 30–60 MeV using the stacked foil technique. In the cases of the 121Sb(α, n)+ 123Sb(α, 3n) and 121Sb(α, 2n)+ 123Sb(α, 4n) reaction pairs, the excitation functions for individual reactions were deduced using theoretical calculations. Excitation functions are also calculated theoretically using the compound-nucleus model with and without the inclusion of a pre-equilibrium emission. As expected, inclusion of a pre-equilibrium contribution based on the exciton model along with compound-nucleus calculations using the Hauser–Feshbach formalism reproduces well the measured excitation functions. Analysis of the data indicates a preference for a first chance neutron emission over charged-particle emission, and interesting trends in the energy and mass-number dependence of the pre-equilibrium fraction are observed.
The quark confinement in extended gauge theory
Authors: Rana J. M. S. , Chandola H. C. , Rajput B. S.
Published: April 2011

To investigate the possible physical implications of the topological structure of non-Abelian dyons in connection with the issue of quark confinement in quantum chromodynamics (QCD), extended gauge theory is formulated in SU(2) and SU(3) gauge groups from the corresponding restricted chromodynamics (RCD) by reactivating the suppressed dynamical degrees of freedom and constructing the gauge potential in terms of the binding gluons (the RCD piece) and the valence gluons (the reactivated piece). It is shown that in this extended QCD, the confinement mechanism of the corresponding RCD remains intact. The physical spectrum contains color-singlet generalized electric glueballs made of valence gluon pairs as well as the generalized magnetic glueballs as massive collective modes of the condensed vacuum.
Phonon dispersion studies in liquid Na–Cs alloy
Authors: Rao R. V. Gopala , Venkatesh R.
Published: April 2011

The Ashcroft empty-core model is used to derive the partial potentials of Na-Cs alloy through a pseudopotential approach. The potential functions are calculated at different concentrations of Cs. From the partial potentials an effective potential is computed. It is in general found that the mixed potential [Formula: see text] lies in between that of the pure metals, namely, [Formula: see text] and [Formula: see text]. The effective potential along with g(r) of the alloy is used to evaluate the longitudinal- and transverse-phonon frequencies in the momentum space through the use of Takeno and Goda's equations. It is found that longitudinal-phonon frequencies ωL(k) show collective excitations even at large values of k while the transverse phonons ωT(k) reach a constant value quickly. Further it is found that the first minimum in the ωL(k) curve appears to coincide with the first peak position in the total structure of the alloy. This is found to be true at all concentrations. Similar observations have been made by other researchers. As a typical illustration the elastic moduli, namely, C11 and C44 are evaluated by different methods for 50 at.% Cs. These methods involve the use of the first and second derivatives of the effective potential. The values calculated show a fair interconsistency proving the veracity of the derived potential function.
The Rayleigh–Taylor instability in magnetic fluids and nonlinear interfacial waves
Authors: Elhefnawy Abdel Raouf F.
Published: April 2011

The nonlinear evolution of a horizontal interface separating two magnetic fluids of different densities, including surface tension effects, is investigated. The fluids are considered incompressible and inviscid, being stressed by the force of gravity, the normal magnetic field, and a constant acceleration in a direction normal to the interface. The method of multiple-scale perturbations is used to obtain two nonlinear Schrödinger equations describing the behavior of the perturbed system. The stability of the perturbed system is discussed both analytically and numerically, and the stability diagrams are obtained. We also obtain the nonlinear cutoff wave number, which separates the region of stability from that of instability.
Considerations of a classical model for spontaneous emission in a nonhomogeneous medium
Authors: Reid André , Piché Michel
Published: April 2011

The classical model for spontaneous emission from a source embedded in a nonhomogeneous medium is examined in a new light. It is shown that the general solution may be expressed in terms of an effective polarizability associated with the transition being modeled. The case of a transition occurring in the vicinity of a perfect mirror is then studied as an illustration. Analytical expressions for the frequency shift and changes in the transition rate as a function of distance are found.
Amplitude distribution statistics of acoustic emission signals
Authors: Ficker T.
Published: April 2011

A satellite structure of the statistical distribution of amplitudes of passive acoustic emission signals is described. Amplitudes of each signal are divided into defined groups, called generations, which represent certain acoustic emission modes. For each generation the corresponding amplitude distribution is determined. All these distributions show a clear satellite structure that is approximated by the weighted average of the Gaussian distributions centered on the satellites.
Causality of relativistic many-particle classical dynamics theories
Authors: Moore R. A. , Qi D. W. , Scott T. C.
Published: April 2011

At the present time, the relativistic many-particle classical dynamics theory of the Fokker–Wheeler–Feynman type for isolated systems admits to two contradictory and mutually exclusive interpretations, noncausal versus causal. This work resolves this contradiction by demonstrating definitively that the mathematical structure of this theory is inconsistent with the assumption of noncausality. The demonstration is effected by identifying the fundamental difference in the input assumptions responsible for the two interpretations, by presenting general arguments proving the deterministic nature of the equations of motion, and by giving explicit examples that not only display the deterministic nature of the equations of motion but also their causal character, namely, being solvable by a stepwise forward in time integration using solely past information. One concludes, first, that the assumption of noncausality, and related deductions, is invalid and must be rejected and, second, that one has, at last, the relativistic generalization of many-particle nonrelativistic classical dynamics based on a Hamilton's principle and with a Lagrangian structure. Thus, one can sensibly proceed to examine the physical implications.
Pulsed electro-optic modulation for efficient, active continuous-wave laser mode-locking
Authors: Flood C. J. , Giuliani G. , Driel H. M. van
Published: April 2011

We demonstrated efficient active mode-locking of a Nd:YAG laser using broad bandwidth, pulsed electro-optic modulation. A 10 GHz, LiTaO3 traveling wave phase modulator, driven by 300 ps FWHM electrical pulses with less than 1 mW of drive power, was used to generate detector-limited, mode-locked laser pulses of less than 50 ps duration at 76 MHz. Shorter modulator drive pulses are possible and near bandwidth-limited mode-locked pulses should be attainable. The use of pulsed modulation rather than conventional sinusoidal modulation permits both pulse width and pulse build-up time reductions and generally makes active mode-locking competitive with passive mode-locking for relatively low-gain and narrow-bandwidth lasers.
WKB approximation for the rotating Morse oscillator
Authors: Varshni Y. P.
Published: April 2011

The WKB approximation is applied to the rotating Morse oscillator. Results are presented for the ground state of the H2 molecule and are compared with those obtained by several other methods. The WKB method gives the best results for v > 5. At smaller values of v, the WKB results are only slightly less accurate than the best ones.
The Feynman chessboard in a box
Authors: Ord G. N.
Published: April 2011

We propose a formulation of the Feynman chessboard model, which explicitly allows for spatial inhomogeneity. We use this formulation to solve the model for a particle confined to a periodic box. The resulting propagator is the Dirac propagator expressed as a Fourier series.
Superfluidité excitonique dans Cu2O
Authors: Mysyrowicz A. , Fortin E.
Published: April 2011

The transit time of excitons through several millimeters of Cu2O is measured by the photovoltaic effect. A sudden reduction of velocity dispersion at high particle density and low temperature is attributed to superfluid excitonic motion.
Simple semi continuous holographic optical elements
Authors: Lemelin Guylain , Lessard Roger A.
Published: April 2011

Using a binary computer-generated hologram (BCGH) made of different thin stripes, one can modify its phase and amplitude pattern and in turn correct and redirect a scanning beam. If the scanning beam is larger than one single stripe, the segmented phase function looks like a continuous one for the incident beam and a smooth curve is reconstructed in space. We show a very simple BCGH that permits the study of the interesting characteristics of this type of computer generated hologram (CGH) at low cost. Numerical as well as experimental results are discussed. This method is very promising in developing large-scale CGHs, holographic display systems, and optical interconnects.
Optimization of the surface morphology of GaAs epitaxial layers grown by close-spaced vapor transport
Authors: Huang Z. , Guelton N. , Cossement D. , Guay D. , Saint-Jacques R.G. , Dodelet J. P.
Published: April 2011

GaAs epitaxial layers were grown on (100) GaAs and vicinal substrates (2° off (100) toward (110)) by close-spaced vapor transport (CSVT) using water vapor as transport agent. We demonstrate that the temperature at which water vapor is injected into the reactor, Tinj, is a criticial parameter for the layer morphology. Furthermore, the optimum Tinj, is a function of water partial pressure, [Formula: see text]. For each [Formula: see text], there is a Tinj range for which specular layers are obtained. This range is defined for [Formula: see text] Torr (1 Torr = 133.3 Pa). The only defects appearing on the specular layers grown on (100) GaAs substrates are oval hillocks (structureless oval defects, and occasionally oval plateaus and oval defects with a faceted central core head). All oval hillocks have their long axis, L1, parallel to < 110 >. By measuring L1 and L2 (the short axis of the defect, perpendicular to L1), lateral growth rates of GaAs are obtained. They vary with [Formula: see text]. At high [Formula: see text], [Formula: see text] is 1 at low water vapor pressure. All oval hillocks result from the contamination of the substrate surface. By using vicinal GaAs substrates, the oval hillock density was decreased to about 500 cm−2, a result similar to that obtained with molecular beam epitaxy.
Charge-induced effects in the spectra of mixtures of solid H2, D2, and HD
Authors: Miller J. J. , Brooks R. L. , Hunt J. L.
Published: April 2011

Proton-beam irradiation of mixtures of solid hydrogens, specifically H2 in D2 and H2 in HD, were studied using infrared absorption spectroscopy. Mixture ratios from 5–50% H2 in D2 near 4.2 K represent the ratios of most interest. This study allows direct comparison of the Stark-shifted lines (caused by negative charges, Q1− of H2and D2 in the same sample. These lines occur in different spectral regions but were thought to have a common cause. Analysis of spectral intensities, as well as timing behaviour as the proton beam is turned off, indicates that the mechanisms giving rise to charge-induced effects are somewhat more complicated than previously thought.
Photoelectronic properties of YBa2Cu3O6
Authors: Ullrich Bruno , Kulaç Ibrahim , Pint Harald
Published: April 2011

The photocurrent and luminescence properties of thin (1 μm) YBa2Cu3O6 films on sapphire at 77 and 300 K are reported. We demonstrate that the luminescence mechanism of YBa2Cu3O6 depends considerably on the wavelength of the excitation used. Completely different luminescence responses are observed with the 351 and 458 nm lines. A fair agreement, like that in semiconductors with band-to-band transitions, is found between photocurrent and luminescence excited by the 458 nm line. The influence of high electric fields (≤ 5 780 V cm−1) on the photocurrent and luminescence of YBa2Cu3O6 is investigated for the first time. Similar effects on photon-induced tunneling phenomena (Franz–Keldysh effect) are observed. However, we show that the observed effects cannot be explained by photon-induced tunneling phenomena only since the influence of an electric field on the band structure of YBa2Cu3O6 is not only restricted to a bending of bands but modifies the band structure in a more complex manner.
High-temperature burn-up of a homogeneous combustible gas mixture from an instantaneous heat source.
Authors: Frolov Alexei M.
Published: April 2011

The high-temperature burn-up problem is studied for an instantaneous heat source inside a combustible gas mixture. Three geometric forms of the heat source are considered: point, straight line, and plane. The appropriate bum-up equation is derived in each case and a simple analytical procedure is given to predict the high-temperature burn-up of a homogeneous combustible gas mixture. The results obtained apply to a high-temperature burn-up in the deuterium–tritium mixture.
On nonintegral E corrections in perturbation theory: application to the perturbed Morse oscillator
Authors: Kobeissi Hafez , Kobeissi Majida , Trad Chafia H.
Published: April 2011

A new formulation of the Rayleigh–Schrödinger perturbation theory is applied to the derivation of the vibrational eigenvalues of the perturbed Morse oscillator (PMO). This formulation avoids the conventional projection of the Ψ corrections on the basis of unperturbed eigenfunctions [Formula: see text], or the projection of the nonhomogeneous Schrödinger equations on [Formula: see text], it gives simple expressions for each E correction [Formula: see text] free of summations and integrals. When the PMO is characterized by the potential U = UM + UP (where UM is the unperturbed Morse potential), the eigenvalue of a vibrational level ν is given by: [Formula: see text]. According to the new formulation the correction £, [Formula: see text] is given by [Formula: see text], where σp(r) is a particular solution of the nonhomogeneous differential equation y″ + f y = sp; here [Formula: see text], sp is well known for each p: for p = 0, [Formula: see text]; for [Formula: see text]. For the numerical application one single routine is used, that of integrating y″ + f y = s, where the coefficients are known as well as the initial values. An example is presented for the Huffaker PMO of the (carbon monoxide) CO-X1Σ+ state. The vibrational eigenvalues Eν are obtained to a good accuracy (with p = 4) even for high levels. This result confirms the validity of this new formulation and gives a semianalytic expression for the PMO eigenvalues.
Vibration–rotation calculations for using a Morse-based discrete variable representation
Authors: Watson James K. G.
Published: April 2011

The Hamiltonian operator for the X3 symmetric triatomic molecule, using Eckart axes with the three internuclear distances as internal coordinates, is derived and applied to numerical calculations of the vibration–rotation spectrum of [Formula: see text]. A C2ν-symmetrized discrete variable representation based on Morse functions is employed for the J = 0 vibrational problem. The unphysical points with ri < 0 or ri + rj < rk are avoided by giving them a large potential energy (106 cm−1). This procedure is not exact, but is adequate for vibrational levels well below the barrier to linearity. The matrices of the complete Hamiltonian in a D3h-symmetrized basis of products of the lowest 50 vibrational eigenvectors with the complete set of rotational functions for each J are set up and diagonalized, and the eigenvectors are used to calculate line strengths. Initially, the well-known potential surface of Meyer et al. (1986) was employed. Subsequently, 7 of the 30 coefficients in this potential were adjusted to give a least-squares fit to the published observed lines of [Formula: see text].
The effect of a radial magnetic field on the stability of Couette flow
Authors: Ali M. A.
Published: April 2011

The effect of a radial magnetic field on the stability of an electrically conducting incompressible fluid between two concentric rotating cylinders is considered. The eigenvalue problem for determining the critical Taylor number TC and the corresponding wave number aC is solved numerically for different values of ±μ(= Ω2/Ω1), (where Ω1, and Ω2 are me angular velocities of the inner and outer cylinders, respectively) and for different gap sizes. It is observed that the radial magnetic field stabilizes the flow. This effect is more pronounced for cylinders that are corotating as compared with counter-rotating cylinders or the situation where only the inner one is rotating.
An efficient fulleride production system
Authors: Datars W. R. , Galts S. , Olech T. , Ummat P. K.
Published: April 2011

A complete system for the production of the fullerides C60 and C70 is described. Emphasis is placed on efficient, continuous production of high-quality materials. Carbon soot with a content of 2–5% of a mixture of C60 and C70 is prepared from carbon rods with an arc furnace. The mixture is separated from the carbon by using a Soxhlet extractor. The C60 and C70 are separated with a chromotography column in which the solvent is cycled continuously. The separated C60 is purified by sublimation. The C70 is separated from heavier fullerides with a second chromotography procedure. Single crystals of C60 are prepared from pure C60 powder by slow sublimation. The C60 is characterized by mass spectroscopy, X-ray diffraction, and Raman and infrared spectroscopy. Typical data obtained with these techniques are shown.
Backside gettering of Cu by porous Si
Authors: Roorda S. , Morin B. , Soudée E. , Gujrathi S. C.
Published: April 2011

Porous Si can act as a getter for Cu. In this experiment, Cu was deposited on the front surface of a Si wafer, after a part of the back surface of the same wafer had been rendered porous. Following a vacuum anneal treatment (900 °C, 2 h), ion scattering shows that some Cu has diffused through the Si wafer and that up to 0.8 × 1016 atoms cm−2 can be gettered in the porous Si layer opposite the deposited Cu.
Analysis of the (5d8 + 5d76s)–5d76p transitions of seven-times-ionized bismuth: Bi VIII
Authors: Kildiyarova R. R. , Joshi Y. N. , Lumsden M. A. , Raassen A. J. J.
Published: April 2011

The spectrum of bismuth was photographed in the 400–1200 Å (1 Å = 10−1 m) wavelength region on a 3 m normal incidence spectrograph using a triggered spark source. The 5d8, 5d76s, and 5d76p configurations of Bi VIII were analysed. The missing 1S0 level of the 5d8 configuration, 27 of 38 levels of the 5d76s configuration, and 30 additional levels of the 5d76p configuration were established. One previously identified level at 338 016 cm−1 (J = 3) was revised to 338 701 cm−1. Two hundred and sixty-three lines were classified in the 5d76s–5d76p transition array, and 26 additional lines were classified in the 5d8–5d76p transition array. The least-squares-fitted parametric calculations interpret the observed spectrum satisfactorily. The scaling factors of the energy parameters were compared in the isoelectronic sequence from Au IV to Bi VIII.
Two-photon widths from the Bethe–Salpeter wave function
Authors: Guiasu Ileana , Koniuk Roman
Published: April 2011

Two-photon widths of pseudoscalar quarkonium are calculated using a Bethe–Salpeter wave function, recently proposed by Gromes. The results are compared to the standard, nonrelativistic quark-model predictions. The nonrelativistic quark model requires a phenomenological mass-dependent factor to bring its calculated pion width in agreement with the experimental data. We find that the Bethe–Salpeter approach, even using a very simple model wave function, gives results that are close to the experimental data for the pion and at the same time the successful nonrelativistic quark-model predictions for heavier systems are not disturbed.
Systematic study of persistent currents in small systems: geometry and interactions
Authors: Johnson B L , Kirczenow G
Published: April 2011

The persistent current is calculated via an exact numerical diagonalization technique for both one- and two-dimensional-model geometries, with an emphasis on the effects of interactions. We find that the interactions can enhance the persistent current for the case of strong diagonal disorder by screening the on-site disorder potential. The screening effect is demonstrated by showing that for a particular configuration of disorder the many-body ground-state, which, for strong disorder, in the absence of interactions will fully occupy only the lowest energy sites, becomes more homogeneous with increasing interaction strength. We also show that the persistent-current vs.flux curves take on the qualitative character of the noninteracting, no-disorder curves for the same structure and filling, which is consistent with the screening mechanism.PACS Nos. 71.10.+x,31.10.+z
Article
Authors: Karshenboim S G
Published: April 2011

We examine the Uehling correction to the energy level of some states in the hydrogen-like muonic atom without any expansion over Zα. The result as a function on n is obtained in closed analytic form for a state with l=n-1 and j=l+1/2. PACS Nos.: 31.20D and 12.20D
Increasing pull-out capacity of granular pile anchors in expansive soils using base geosynthetics
Authors: Kumar B R. Phani , Rao N Ramachandra
Published: April 2011

Granular pile anchors are innovative and effective in resisting the uplift pressure exerted on the foundation by a swelling expansive soil. In a granular pile anchor, the foundation is anchored at the bottom of the granular pile to an anchor plate with the help of a mild steel rod. This renders the granular pile tension-resistant and enables it to offer resistance to the uplift force exerted on the foundation by the swelling soil. This resistance to uplift or pull-out load depends mainly upon the shear parameters of the pile-soil interface and the lateral swelling pressure of the soil, which confines the pile radially and prevents it from being uplifted. The resistance to uplift can be increased by placing a base geosynthetic above the anchor plate so that it forms an integral part of the granular pile anchor. The increase in resistance is due to the friction mobilized between the geosynthetic and the confining media when the uplift load acts on the pile and the geosynthetic moves along with the pile. Hence it depends on the friction between the geosynthetic and the confining media and the area and stiffness of the geosynthetic. This paper discusses the effects of these parameters on pull-out load, rate of heave, and relative ground movement near the pile surface.Key words: expansive soil, granular pile anchor, base geosynthetic, ground movement, rate of heave, pull-out load.
Constitutive models of frozen soil
Authors: He Ping , Zhu Yuanlin , Cheng Guodong
Published: April 2011

The constitutive models on viscoelastoplasticity and the damage to frozen soil presented in this paper can be used to analyze the relationship of stress and strain, under complicated stress states, and damage development and the failure process of the internal structure of frozen soil. The models successfully predict the whole process of creep, including the failure stage. Both strengthening and weakening effects of confining pressure, namely increasing the friction force between soil particles and decreasing the frozen force between ice and the soil particles due to pressure melting of ice, are considered in the constitutive models.Key words: viscoelastoplasticity, damage development, constitutive model, frozen soil.
Prediction of the horizontal load-displacement curves of pile groups based on the results of single pile tests
Authors: de Sousa Coutinho António GF
Published: April 2011

This paper presents the prediction of horizontal load-displacement curves of pile groups based on the results of single pile tests. Although the same basic model is employed, two different approaches are taken: one assumes soil to be linear elastic-plastic, and the other assumes it to be elastic nonlinear. The model is calibrated on the basis of the results of a full-scale single pile test. Special emphasis is placed on model calibrations, since the success of any prediction method depends on a careful characterization of the soil. Some new approaches for determining the soil parameters are presented. Two methods for predicting load-displacement curves, one from each model approach, are then proposed and discussed. Special emphasis is placed on group efficiency in the elastic-plastic method and on the boundary conditions of the single pile and the pile group in the elastic nonlinear method. Using the soil characteristics from the model calibrations, the load-displacement curves for a given pile group are then predicted. These predictions are compared with the results of a full-scale pile group test carried out at the same site as that of the single pile test. Agreement between the predictions and the test results tends to validate the methods proposed.Key words: displacement predictions, pile groups, model calibration, pile tests.
Modelling hydraulic conductivity in a small centrifuge
Authors: Singh Devendra N , Gupta Ashok K
Published: April 2011

Hydraulic conductivity modelling has been carried out using various conventional laboratory 1g tests and centrifuge tests for different compaction states of a silty soil. It has been shown that hydraulic conductivity is modelled adequately in the centrifuge.Key words: silty soil, hydraulic conductivity, centrifuge modelling, falling-head tests, consolidation tests, scale factor.
A method for assessing the relative likelihood of failure of embankment dams by piping
Authors: Foster Mark , Fell Robin , Spannagle Matt
Published: April 2011

A method for estimating the relative likelihood of failure of embankment dams by piping, the University of New South Wales (UNSW) method, is based on an analysis of historic failures and accidents in embankment dams. The likelihood of failure of a dam by piping is estimated by adjusting the historical frequency of piping failure by weighting factors which take into account the dam zoning, filters, age of the dam, core soil types, compaction, foundation geology, dam performance, and monitoring and surveillance. The method is intended only for preliminary assessments, as a ranking method for portfolio risk assessments, to identify dams to prioritise for more detailed studies, and as a check on event-tree methods. Information about the time interval in which piping failure developed and the warning signs which were observed suggest that the piping process often develops rapidly, giving little time for remedial action. In the piping accidents, the piping process reached some limiting condition allowing sufficient time to draw down the reservoir or carry out remedial works to prevent breaching.Key words: dams, failures, risk, probability, piping.
Finite element modeling of hexagonal wire reinforced embankment on soft clay
Authors: Bergado D T , Teerawattanasuk C , Youwai S , Voottipruex P
Published: April 2011

A full-scale test embankment was constructed on soft Bangkok clay using hexagonal wire mesh as reinforcement. This paper attempts to simulate the behavior of the full-scale test embankment using the finite element program PLAXIS. The agreement between the finite element results and the field data is quite good. The important considerations for simulating the behavior of the reinforced wall embankment were the method of applying the embankment loading during the construction process, the variation of soil permeability during the consolidation process, and the selection of the appropriate model and properties at the interface between the soil and reinforcement. The increased reinforcement stiffness tends to increase the reinforcement tension and increase the embankment forward rotation. The reinforcement tensions increased with the compression of the underlying soft foundation. The appropriate interface properties between the backfill soil and the hexagonal wire mesh reinforcement corresponding to the interaction mechanism at working stress conditions were dominated by the direct shear mechanism. The direct shear interaction coefficient of 0.9 was used.Key words: soil reinforcement, hexagonal wire mesh, finite element analysis, field embankment.
A sliding block model for the runout prediction of high-speed landslides
Authors: Miao Tiande , Liu Zhongyu , Niu Yonghong , Ma Chongwu
Published: April 2011

A sliding block model is developed for predicting the runout of high-speed slide-like landslides, based on the analysis of the dynamic mechanism of high-speed landslides. This model adopts the limit equilibrium analysis approach and incorporates mass dynamics and soil deformation into the calculation of soil movements. The critical state is considered as the initial stress state, and the interslice forces are obtained considering the equivalence of deformation energy. It is possible, applying this model, to simulate the whole travel process of the soil mass from the onset of the landslide and to predict the travel speed of the soil mass and the hazard area of the landslide. Application of the model to the Sale Mountain landslide and the Tianshui Forging Machine Factory landslide in China gives reasonable results in comparison to the field observations. The calculated results illustrate that (i) the fundamental causes of the high speed are the decline of the resultant friction force during sliding and the rapid and large fall of the centre of gravity of the back part of the slide mass; and (ii) the slide mass generally moves as a whole during the middle sliding stage, and the front part of the slide mass is often in a state of relaxation, even extension, at the end of the movement.Key words: high-speed landslides, dynamic analysis, runout distance, block model.
Prediction of residual driving stresses in piles
Authors: Costa Licia Mouta da , Danziger Bernadete Ragoni , Lopes Francisco de Rezende
Published: April 2011

Residual driving stresses in piles are determined with a new stress-wave program. The program has some interesting features, such as the displacement stabilization accomplished by an analysis for a longer time, until zeroing particle velocity at the pile toe. A parametric study of the development of residual stresses in a steel pile shows interesting aspects related to the effects of toe resistance, shaft friction resistance distribution, and driving energy. A comparison is made between the application of available solutions and the new program.Key words: residual stresses, pile driving, foundation, analysis.
The performance of a laboratory facility for evaluating the structural response of small-diameter buried pipes
Authors: Brachman R WI , Moore I D , Rowe R K
Published: April 2011

The performance of a new laboratory facility for testing small-diameter buried pipes (less than 300 mm diameter) subject to the biaxially compressive earth pressures expected to prevail under deep and extensive overburden is examined. The new facility consists of a prism of soil 2.0 m wide × 2.0 m long × 1.6 m high contained within a stiff steel structure. Laboratory tests were performed in the new test facility to examine the appropriateness of the boundary conditions imposed during testing. Overburden pressures are successfully simulated with a pressurized air bladder. Boundary friction was limited to only minimal effects with lubricated polyethylene sheets. The stiffness of the lateral boundary is sufficiently large to induce lateral stresses close to those for zero lateral strain conditions. Overall, the effects on the pipe arising from the idealizations involved in the laboratory model were found to be small. The application of the new test cell is illustrated by using it to assess the response of a small-diameter landfill leachate collection pipe under two different backfill conditions. This comparison showed that the structural response of the pipe is significantly impacted by the coarse gravel backfill used in landfill drainage layers. Maximum pipe deflections and strains were nearly twice as large when tested in the coarse gravel compared with the sand backfill. Much greater variations of deflection and strain were also measured with the coarse gravel when compared with the sand backfill due to local bending effects from the coarse gravel.Key words: buried pipes, soil-structure interaction, laboratory testing, leachate collection pipes.
Influence of laterally loaded sleeved piles and pile groups on slope stability
Authors: Ng C WW , Zhang L M , Ho K KS
Published: April 2011

Many high-rise buildings, bridges, and transmission towers are constructed on steep slopes in Hong Kong and are supported by large-diameter piles. These structures may be subjected to large lateral loads, such as those caused by typhoons, earthquakes, and high-speed vehicles. The margin of safety of the slope may decrease as a result of stresses transferred from the piles to the slope. To minimize the transfer of lateral load from the buildings to the shallow depths of the slope, an annulus of compressible material (sleeving) is sometimes formed between the piles and the adjacent soils. In this paper, a three-dimensional analysis is carried out to investigate the effects of unsleeved and sleeved single piles and pile groups on the stability of a cut slope. Mechanisms of load transfer from the piles to the slope are studied. The stability of the slope is evaluated using the strength reduction technique. The evolution of slope failure is examined and the factors of safety for both initiation of instability and global failure of the slope are identified from the numerical analyses. The sleeving technique is found to be capable of significantly reducing the stresses in the shallow depths of the slope in front of the piles, thus improving the local stability of the slope, but offers limited benefit with respect to global stability.Key words: laterally loaded pile and pile group, sleeving, slope stability, three-dimensional analysis, load transfer mechanism, factor of safety.
Defining an appropriate steady state line for Merriespruit gold tailings
Authors: Fourie A B , Papageorgiou G
Published: April 2011

Failure of the Merriespruit gold tailings dam in 1994 in South Africa was unusual in that never before had a gold tailings dam in South Africa failed in such a catastrophic fashion. Conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading, primarily because of the method of deposition which allows significant consolidation to occur due to sun-drying. This paper demonstrates that the concept of a steady state line, which separates dilative from contractive behaviour upon undrained loading, is applicable to Merriespruit tailings. Four particle-size distributions of Merriespruit tailings were tested to determine the influence of the percent finer than 75 µm on the position of the steady state line. The tailings with the greater percentage of fines gave a steady state line that plotted above all the others, which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low-fines tailings samples. The difficulty of defining a unique steady state line for a particular tailings, due to errors in measurement of initial sizes, is illustrated and it is recommended that error bands be assigned to any steady state line. In a companion paper, evidence from the post-failure investigation is combined with the test results in this paper to explore the likelihood of static liquefaction as the cause of the Merriespruit flow failure.Key words: static liquefaction, tailings, steady state, flow failure.
An investigation of scaling and dimensional analysis of axially loaded piles
Authors: Sedran Gabriel , Stolle Dieter FE , Horvath Robert G
Published: April 2011

This paper investigates the use of the concepts of similarity and dimensional analysis to interpret results from reduced-scale models of axially loaded piles embedded in sand. These concepts are reviewed in the light of a pilesoil system and its response to static or half-sine impulsive loading. It is suggested that constitutive similarity between model and prototype responses can be fulfilled without scaling gravity, provided that a stress scaling factor equal to one is selected. The scaling factors are validated with numerical simulations via finite element analyses by comparing the results from full-scale and special reduced-scale pilesoil models. It is also shown that a frustum confining vessel has the potential to provide more realistic scaled responses than are obtained with the classical 1g devices. A series of pile test responses are simulated for different pile lengths and different coefficients of lateral earth pressure. A set of scaling factors is presented and a particular set of dimensionally homogeneous π groups is proposed to characterize the behaviour of the pilesoil system. Simulated responses are interpreted using the proposed π groups to obtain functional relations relevant to the pilesoil problem.Key words: reduced-scale modelling, dimensional analysis, similarity, model piles, sands.
Groundwater control around a large basement
Authors: Ervin M C , Morgan J R
Published: April 2011

Melbourne's Crown Casino was constructed on a site bordering the Yarra River and underlain by problem soils of the Coode Island Silt Formation. The development needed to provide two levels of basement car park over the entire site. An innovative approach to groundwater control around the excavation was required to avoid depressurisation of adjoining soils, leading to settlements. Analysis showed a conventional bentonite cut-off wall would still allow depressurisation by lateral flow through the Coode Island Silt during the construction period. The high cost and construction difficulty of a very low permeability wall mitigated against it. An hydraulic wall was proposed in conjunction with a conventional cut-off wall. This comprised a curtain of wick drains surrounding the cut-off wall and charged with water. Control of seepage through an underlying aquifer by a cut-off wall was considered, but a more cost-effective method using recharge by wells was adopted when shown necessary. Monitoring of groundwater pressures around the site showed that the maximum change in water pressure was less than 1 m head, the design criterion. Part way through construction, recharge was initiated when monitoring of the deep aquifer showed pressure reduction attributed to vertical leakage through a basalt tongue.Key words: excavation, basements, groundwater, clays, settlement, monitoring.
Analytical model of interaction between hexagonal wire mesh and silty sand backfill
Authors: Bergado D T , Voottipruex P , Srikongsri A , Teerawattanasuk C
Published: April 2011

The interaction behavior between hexagonal wire mesh and silty sand backfill can be evaluated from pullout tests. The pullout resistance of the hexagonal wire mesh reinforcement consists of two components, namely friction resistance and passive bearing resistance. The friction resistance  relative displacement relationship of a hexagonal wire mesh can be simulated by a linear elastic  perfectly plastic model. The passive bearing resistance of an individual bearing member can be modelled by a hyperbolic function. The friction resistances for galvanized and PVC-coated hexagonal wire mesh were 25 and 21%, respectively, of the total pullout resistance. A new analytical model for predicting the pullout resistance of hexagonal wire mesh reinforcement has been proposed. The proposed solution can estimate the maximum pullout force at different reinforcement levels from observed horizontal movement of a hexagonal wire mesh reinforcement.Key words: hexagonal wire mesh, necking phenomena, bearing resistance, analytical model, pullout box, bearing resistance.
A numerical study of the bearing capacity factorNγ
Authors: Zhu D Y , Lee C F , Jiang H D
Published: April 2011

Values of the bearing capacity factor Nγare numerically computed using the method of triangular slices. Three assumptions of the value of ψ, the base angle of the active wedge, are analyzed, corresponding to the following three cases: (1) ψ = ϕ, the internal friction angle; (2) ψ = 45° + ϕ/2; and (3) ψ has a value such that Nγis a minimum. The location of the critical failure surface is presented and the numerical solutions to Nγfor the three cases are approximated by simple equations. The influence of the base angle on the value of Nγis investigated. Comparisons of the present solutions are made with those commonly used in foundation engineering practice.Key words: shallow foundation, bearing capacity, bearing capacity factor, limit equilibrium.
Use of in situ penetration tests in pavement evaluation
Authors: Konrad J -M , Lachance D
Published: April 2011

This paper presents the results of an extensive field investigation of several instrumented road sections in the Province of Quebec, Canada. Falling-weight deflectometer tests, static load tests on embedded plates at different depths, large dynamic cone penetration (DCP) tests, and piezocone tests (CPTU) were performed to study the mechanical response of the pavement. A correlation between elastic deformation modulus inferred from the plate load tests and DCP penetration index was obtained for nine different sites. A correlation between the equivalent elastic modulus of uniform subgrade soils and piezocone tip resistance was also established using data from the falling-weight deflectometer. A procedure for calculating the deflection basin for any pavement system placed over a more complex subgrade stratigraphy was proposed using these correlations. The proposed procedure was validated on two sites and its performance was adequate, since the calculated deflection basins agreed well with the measured deflection basins.Key words: penetration test, piezocone, deflection, pavement, in situ.
An efficient search method for finding the critical circular slip surface using the Monte Carlo technique
Authors: Malkawi AI Husein , Hassan W F , Sarma S K
Published: April 2011

Locating the critical slip surface and the associated minimum factor of safety are two complementary parts in a slope stability analysis. A large number of computer programs exist to solve slope stability problems. Most of these programs, however, have used inefficient and unreliable search procedures to locate the global minimum factor of safety. This paper presents an efficient and reliable method to determine the global minimum factor of safety coupled with a modified version of the Monte Carlo technique. Examples are presented to illustrate the reliability of the proposed method.Key words: factor of safety, method of search, critical slip surface, circular, global, Monte Carlo.
Hydraulic conductivity of bentonite permeated with acid mine drainage
Authors: Kashir Mansor , Yanful Ernest K
Published: April 2011

Bentonite, especially sodium bentonite, is used extensively either by itself or as a component of soil mixtures in many geoenvironmental engineering applications, including the construction of waste-containment barriers. An important aspect of the design of such barriers is the compatibility assessment of the soil barrier with the intended waste. A series of laboratory hydraulic conductivity (K) experiments were conducted to assess the compatibility of a sodium bentonite paste with acid mine drainage (AMD). The K of the water-permeated bentonite was observed to be of the order of 2 × 109cm/s. Permeation of the bentonite with AMD increased K slightly by almost one order of magnitude to an average value of 1 × 108cm/s as a result of the contraction of electrical double layers surrounding clay particles. The application of a confining stress (3050 kPa) to the samples minimized the increase in K. Confining stress likely compressed the samples and reduced the size of the voids created by double-layer contraction, resulting in lower K. Effluent chemical profiles obtained during the K tests indicated the appearance of some cations and elements contained in the AMD permeant, at its original concentration (influent concentration) after a few pore volumes of AMD permeation. Iron and aluminum likely precipitated as oxyhydroxide and oxysulphate minerals. The pH of the effluent decreased from 7.6 during water permeation to 3.0 after only three pore volumes of AMD permeation, reflecting the limited capacity of the bentonite to neutralize acidic solutions. Zinc was slightly attenuated by adsorption (3.15 mequiv./100 g of dry bentonite) but was reported in the effluent, after approximately nine pore volumes. The results are relevant to the design and construction of bentonite slurry walls around acid-generating tailings and acid water containment ponds at mine sites.Key words: hydraulic conductivity, swelling, waste containment, confining stress, heavy metals, ionic strength, saturation index.