bluuebunny/crossref_metadata_2025 huggingface dataset:
Earthquake response at Grangemouth
Authors: Papastamatiou D. , Pappin J. W. , Richards J. A. , Sweeney M.
Published: October 2009

The Grangemouth industrial zone in Scotland is on an area of deep soft clay. Extensive site investigations related to industrial development which included seismic cone testing enabled accurate numerical calculations to be carried out to assess the response of this soft site to earthquake excitation. The site is surrounded by the permanent LOWNET seismological array, which together with a temporary seismic station at the site enabled comparison between numerical predictions and instrumental experimental evidence. The comparisons confirmed the predominance of the site dynamic response in earthquake ground surface motions. They also enabled a site-specific design response spectrum to be developed with greater confidence.

La zone industrielle de Grangemouth (Ecosse) est située sur une argile molle profonde. Les études extensives réalisées in-situ en vue d'un développement industriel comprenent des essais sismiques au cône. Elles permettent de réaliser des calculs numériques précis afin de connaître la réponse de ce sol mou aux excitations sismiques. Le site est entouré par le dispositif sismique permanent Lownet qui, associé à une station sismique temporaire, permet de comparer les prévisions numériques aux résultats expérimentaux et instrumentaux. Les comparaisons confirment la prédominance des réponses dynamiques du site dans les mouvements sismiques de surface du sol. Elles permettent également de déterminer avec une plus grande fiabilité un modèle de spectre de réponse spécifique du site.
Behaviour of embedded model screw anchors in soft clays
Authors: Rao S. Narasimha , Prasad Y. V. S. N. , Veeresh C.
Published: October 2009

In recent years helical anchors have been used extensively in the construction of transmission tower foundations, pipelines and braced excavations. This Paper describes an experimental programme carried out to show the behaviour of multiple helical anchors at different embedment ratios in soft marine clays. The number of helical plates, their diameters and spacings are varied. Pullout tests were conducted by anchors installed in a soft marine clayey bed prepared in test tanks and at embedment ratios of 0-10. The results indicate that the anchor capacity increases with embedment ratio. The uplift capacity at any embedment ratio is explained in terms of the contribution of cohesive resistance between the top and bottom helical plates, the bearing resistance of the top helical plate alone and the shaft adhesion above. Based on embedment ratio and observations during testing, the anchors are classified as shallow, transit and deep anchors. Formulations are suggested for estimating and calculating the capacities of helical anchors which agree well with the results of previous investigators.

Depuis quelques années, les ancrages hélicoïdaux ont été largement utilisés dans la construction de fondations de tours de transmission, de conduites et d'excavations armées. L'article décrit le programme expérimental mis en oeuvre pour montrer le comportement d'ancrages hélicoïdaux, dans des argiles molles marines, pour différents encastrements. Le nombre des plaques hélicoïdales, leur diamètre et l'espacement entre plaques sont variables. Des essais d'arrachement ont été réalisés sur des ancrages mis en place dans des lits d'argile molle marine préparés dans des cuves expérimentales, et ce pour des valeurs d'encastrement variant de 0 à 10. Les résultats obtenus montrent que la charge admissible des ancrages augmente avec le rapport d'encastrement. La charge verticale pour différents rapports d'encastrement peut être expliquée par une contribution de la résistance de cohésion entre le sommet et la base des plaques hélicoïdales, par la résistance ultime au sommet de la plaque et par l'adhérence latérale au dessus de celle-ci. A partir des rapports d'encastrement et des observations faites au cours des essais, les ancrages ont été répartis en trois groupes: ancrages superficiels, intermédiaires et profonds. Des équations permettant d'estimer et de calculer la charge des ancrages hélicoïdaux sont proposées. Elles se révèlent être en bon accord les résultats trouvés par les autres chercheurs.
Dynamic soil—pile—foundation—structure interaction: records and predictions
Authors: Makris N. , Gazetas G. , Delis E.
Published: October 2009

The problem of soil—pile—foundation—superstructure interaction is examined, and a simple rational procedure to analyse the response of a structure supported on pile groups is presented. This procedure combines theories for the computation of the dynamic impedances and kinematic—seismic response factors of pile foundations with a multi-degree-of-freedom structural model. The procedure is applied to compute the response of a bridge in Rio Dell, California, which was shaken by the M8=7·0 Petrolia earthquake in 1992. The predicted response agrees well with recorded data. The significance of considering the frequency-dependence of the pile foundation impedances in the analysis of the response of the superstructure is discussed.

L’article s’intéresse aux problemes générés par les interactions sol—pieu fondation—superstructure et présente une proc6dure rationelle simple permettant déanalyser la réponse déune structure fondée sur groupes de pieux. Cette procé dure combine les théories disponibles, permettant le calcul des impédances dynamiques et des facteurs de réponse sismique déune fondation sur pieux, à un modèle structural à n degrés de liberté. La procédure a ét´ appliquée à un pont du Rio Dell, en Californie, qui a été soumis en 1992 au séisme de Pétrolia de Ms = 7·0. La réporte prévue correspond bien aux raleun observ´es. L’article montre &avute;galement quéil est importance de considèrer, lors de l’analyse de la r6ponse de la superstructure, que la fréquence est fonction de l’impedance des pieux.
An assessment of a model of heat and moisture transfer in unsaturated soil
Authors: Thomas H. R. , Li C. L. W.
Published: October 2009

An assessment of the validity of a theoretical formulation of coupled heat and moisture in non-deforming unsaturated soil is presented. This was achieved by comparison of results from the theoretical formulation with those obtained from controlled laboratory heating experiments. The work centred on one material, a highly compacted medium sand, for which the thermophysical parameters had been established independently of the heating experiments. A solution of the theoretical formulation was achieved by means of a numerical analysis, using the finite difference method. Very good correlations were achieved between experimental and numerical results. Confidence in the ability of the theoretical formulation to describe fully the physical processes involved is thus enhanced. Application of these conclusions to problems of heat and moisture transfer in non-deforming, cohesionless soils in general is now considered possible. The numerical results were achieved using parallel computing techniques. This methodology was shown to perform very efficiently, yielding a simulation of the full range of the transient behaviour for all the experiments considered. The potential of parallel computing systems for the solution of a computationally demanding problem of this type is thus revealed.

Ľexposé évalue la validité d'une formulation théorique du couplage chaleur-humidité dans un sol non déformant non saturé. Cette évaluation repose sur la comparaison des résultats de la formulation théorique aux résultats d'essais contrôlés de chauffage en laboratoire. Les travaux se sont concentrés sur un matériau: un sable moyen fortement tassé, dont les paramètres thermo-physiques avaient été établis indépendamment des essais de chauffage. On a résolu la formulation théorique à ľaide analyse numérique en utilisant la méthode des différences finies. On a obtenu de triés bonnes corrélations entre les valeurs expérimentales et les valeurs calculées. On a maintenant une plus grande certitude que les formules théoriques peuvent décrire complétement les processus physiques qui entrent en jeu. On pense qu'il est maintenant possible d'appliquer ces conclusions en général aux problèmes du transfert de chaleur et d'humidité dans des sols non déformants sans cohésion. On a eu recours à des techniques de calcul parallèles pour obtenir les valeurs théoriques. Cette méthodologie s'est avérée triès efficace et a permis de simuler la gamme complète des comportements transitoires dans tons les essais envisagés. Cela montre qu'il est possible d'utiliser des systèmes de calcul parallèles pour résoudre un problème de ce type, qui est fort exigeant sur le plan du calcul.
Use of in situ measurements of ground inclination for determining shallow elastic parameters
Authors: Rodríguez-Zúñiga J. L. , Gaulon R. , Blum P. A. , Sánchez-Sesma F. J.
Published: October 2009

We present the application of high-resolution ground inclination measurements to estimate some elastic properties in shallow stratified terrain. The direct problem for the solution of vertical and radial displacements under static loads is illustrated by means of the well-known Boussinesq problem for the elastic half-space. More realistic (stratified) configurations are taken into account by means of the stiffness matrix method proposed by Kausel and Roesset. In order to test our procedure some inclination surveys were performed in the virgin Texcoco Lake zone in Mexico City. Results are presented for the shear wave velocity and depth of the uppermost strata. A good fit between theoretical and observed inclinations was obtained. This leads to improved estimates of the ground parameters studied. Comparisons with results from independent seismic wave refraction profiles and cone resistance values validate our procedure. The agreement between the results from measurements of the ground surface inclination and results from other common, established techniques shows that the former technique provides a good estimate of ground elastic parameters.

Nous montrons comment des mesures à haute résolution du pendage permettent d'estimer certains paramètres d'élasticité de couches superficielles stratifiées. Le probléme direct de la résolution des déplacements verticaux et radiaux sous l'effet de charges statiques est illustré à l'aide de la formule bien connue de Boussinesq pour la masse élastique semi-infinie. On tient compte de configurations stratifiées plus réalistes en utilisant la matrice de rigidité proposée par Kausel et Roesset (1981). Pour Vérifier notre méthodologie, nous avons effectué des relevés de pendage dans la zone vierge du lac Texcoco à Mexico. Nous présentons les résultats obtenus pour la vitesse de l'onde de cisaillement et la profondeur des couches superficielles. Les valeurs théoriques du pendage concordent bien avec les valeurs observées, ce qui veut dire que notre méthode permet d'estimer avec plus de précision les paramétres du terrain étudié.Elie est validée par des comparaisons avec les résultats d'études ind6pendantes de profils de réfraction des ondes sismiques et des valeurs de résistance en pointe. La concordance entre les résultats des mesures du pendage des couches superficielles et les résultats d'autres techniques bien établies montre que les premiéres offrent une bonne estimation des paramétres d'élasticité du sol.
The Rankine Lecture
Authors: Blight G. E.
Published: October 2009

The 37th Rankine Lecture of the British Geotechnical Society was given by Professor G. E. Blight MScEng, DScEng(Witwatersrand), PhD, DScEng (Lond), DScEng(Cape Town) at Imperial College of Science, Technology and Medicine on 19th March, 1997. The following introduction was given by J. B. Burland.
Interpretation of direct shear box testing of sands as quasi-simple shear
Authors: Shibuya S. , Mitachi T. , Tamate S.
Published: October 2009

Interpretation of the direct shear box (DSB) test implicitly assumes a simple shear mode of deformation, but this assumption has not been fully verified, in particular in tests on sands. This paper describes a laboratory investigation, which was commissioned to find an optimum configuration of a DSB apparatus for measuring the strength and dilatancy characteristics in direct simple shear. The examination was made in a newly developed DSB apparatus using dry specimens of two standard sands: Toyoura sand and silver Leighton Buzzard sand. Boundary effects, such as the wall friction, the size of the opening between the two halves of the shear box and the constraint imposed by the loading platen, were each independently examined in pilot tests to determine their influence on the measurements of strength and angle of dilatancy. The optimum configuration was determined through careful examination of the boundary stresses and strains of rectangular specimens subjected to shearing under drained and constant-volume conditions, and also by comparing the results with those of comparative torsional simple shear and plane strain compression tests. On the basis of the test results obtained using an optimum configuration of the DSB device, the stress dilatancy of the sands was characterized by a non-associated rule based on a classical energy theory for the interrelationship between the angle of shearing resistance and the angle of dilatancy.
Stability analysis of embankments: comparison of limit analysis with methods of slices
Authors: Jiang G.-L. , Magnan J.-P.
Published: October 2009

Limit analysis has been firmly established over the past decades and is now considered to be an accurate method for predicting failure mechanisms and for calculating limit loads. A new finite element procedure has been developed, and is briefly described in this paper, to determine automatically the optimal failure mechanism for geometrically complicated structures under applied loads. In limit analysis, the objective is generally to determine the collapse load, whereas the factor of safety is calculated in methods of slices. This paper also shows how the factor of safety introduced in the limit equilibrium analysis can be systematically incorporated into limit analysis. Several computations of stability of embankments were carried out to compare the limit analysis results with those obtained by methods of slices based on the limit equilibrium analysis. Through this investigation, some differences and similarities between these two theories can be demonstrated. The numerical results demonstrate that limit analysis by the present finite element method generally gives factors of safety more accurate than or as accurate as those obtained by methods of slices.
Bifurcation and shear band propagation in sands
Authors: Saada A. S. , Liang L. , Figueroa J. L. , Cope C. T.
Published: October 2009

Under simple or combined stresses, homogeneous sand specimens exhibit localization of deformation followed by shear band formation. This phenomenon has been extensively studied under plane strain loading conditions. This paper studies the initiation and propagation of the shear bands that develop in thin long hollow cylinders of sand subjected to a combination of axial torsional and spherical stresses. Digital image processing techniques are used to observe and measure the displacements and the initiation and development of the shear bands. The effects of the inclination of the principal stresses on the axis of symmetry, the relative density, the confining pressure and granulometry are examined. Strain measurements within the shear bands open the door to a more complete description of the mechanical behaviour of the material, in particular beyond the peak, in the so-called strain softening zone.

L'application de contraintes simples ou complexes à des échantillons homogènes de sable donne lieu à une localization de la déformation sous forme de bandes de cisaillement. Ce phénomène a été largement étudié dans des conditions de déformations planes. Dans cet article on utilise des cylindres creux de sable soumis à des contraintes axiales, torsionelles, et hydrostatiques pour étudier la formation et la propagation de ces bandes de cisaillement. Des techniques basées sur l'analyse digitale d'images sont utilisées pour observer ainsi que pour mesurer les déplacements et l'initiation des bandes. On examine l'influence de l'inclinaison des contraintes principales sur l'axe de Symmetrie, de la densité relative, de la contrainte hydrostatique, et de la granulometrie. La mesure des déformations a l'intérieur des bandes de cisaillement permet de faire une description plus complète du comportement mécanique du matériau; en particulier au-delà du maximum et dans la zone de ramolissement.
A probabilistic approach to sand particle crushing in the triaxial test
Authors: Nakata A. F. L. , Hyde M. , Hyodo H. , Murata
Published: October 2009

Single-particle crushing tests have been carried out on the component minerals of a sand and the results have been compared statistically with those obtained for individually marked particles placed in triaxial samples and then subjected to isotropic consolidation and shear tests. The single-particle crushing strength was defined for breakage of asperities and for whole-particle fracture. The results were analysed and compared using particle survival probability curves. Maximum characteristic stresses were estimated for the individual particles embedded in the test specimens using a simplified analysis and then survival probabilities at these stress levels were abstracted from the curves for the single-particle tests. A statistical comparison with the observed particle breakages showed good agreement. A particle breakage factor was defined in terms of the evolution of the particle size grading curve with respect to the smallest particle size and related to the survival probability curve for the breakage of asperities. The degree of crushing as measured by the change in particle size distribution curves seems to be related to the size of the yield surface, with larger evolved yield surfaces causing more particle breakage.

Nous avons réalisé des essais de broyage à une seule particule sur les minéraux composant un sable et nous avons comparé les résultats de maniére statistique avec ceux obtenus pour des particules marquées individuellement et placées dans des échantillons sur trois axes puffs soumis à une consolidation isotrope et à des essais de cisaillement. Nous avons défini la résistance à écrasement des particules seules pour la fracture des aspériés et pour la fracture de toute la particule. Nous avons analysé les résultats et les avons comparés en utilisant des courbes de probabilité de survie des particules. Nous avons évalué des contraintes caractéristiques maximum pour les particules individuelles enfouies dans les spé cimens d’essai en utilisant une analyse simplifiée ; ensuite, nous avons soustrait de ces courbes les probabilités de survie à ces niveaux de contrainte pour les essais à une seule particule. Une comparaison statistique avec les fractures de particules observées montrait une bonne concordance. Nous avons défini un facteur de fracture de particule en termes d’évolution de la courbe de graduation des particules par rapport à la plus petite pardcule et relativement à la courbe de probabilité de survie pour la fracture des aspériés. Le degré de broyage mesuré par le changement des courbes de distribution des dimensions de particules semble tÊtre lié à la taille de la surface de fiéchissement, les surfaces les plus grandes causant davantage de fracture de particule.
A cyclic elasto-plastic constitutive model for sand considering a plastic-strain dependence of the shear modulus
Authors: Oka F. , Yashima A. , Tateishi A. , Taguchi Y. , Yamashita A.
Published: October 2009

A cyclic elasto-plastic constitutive model based on a non-linear kinematic hardening rule for sand is proposed. Three points are incorporated into the model: a new flow rule, a cumulative strain-dependent characteristic of the plastic shear modulus and a fading memory characteristic of the initial anisotropy of the constitutive model. In order to verify its effectiveness, the proposed model was evaluated by means of the results of a series of hollow-cylinder torsional shear tests with and without an initial shear stress after isotropic and anisotropic consolidation. The liquefaction strength curve, the effective stress path and the stress—strain relation during cyclic loading are well reproduced by the proposed model.

KEYWORDS: constitutive relations; liquefaction; plasticity; repeated loading; sands.

Nous proposons ici un modèle constitutif élastoplastique cyclique basé sur une règle de durcissement cinématique non linéaire du sable. Trois points sont incorporés dans le modèle: une nouvelle règle d'écoulement, une caractéristique cumulative dépendant de la déformation du module de cisaillement plastique et une caractéristique de mémoire évanescente de l'anisotropie initiate du modèle constitutif. Afin de vérifier son efficacité, nous évaluons le modèle proposé en utilisant les résultats d'une série d'essais de cisaillement torsionnel cylindrique creux avec et sans contrainte tangentielle initiale après consolidation isotrope et anisotrope. La courbe de résistance à la liquéfaction, le chemin de contrainte effective tout comme la relation contrainte-déformation pendant le chargement cyclique sont bien reproduits par le modèle proposé.
A study of low-energy dynamic compaction: field trials and centrifuge modelling
Authors: Merrifield C. M. , Davies M. C. R.
Published: October 2009

This paper describes research into understanding the efficiency of the low-energy dynamic compaction process, and the development of a novel technique of real-time monitoring that can demonstrate soil improvement in quantitative engineering units during the process. The research, undertaken in the field and using a 500 gTonne geotechnical centrifuge, investigates the validity of applying the principles of the WAK (wave-activated stiffness [K]) test analysis to monitor the progress of compaction, allowing the process to be halted once the required degree of improvement has been reached. The analytical procedures underpinning the interpretation of the compaction process data in the time and frequency domain are presented, including the derivation of dynamic stiffness, depth of compaction, and damping factors associated with the combined footing/soil system. The methods of instrumentation and data acquisition are described for both field and centrifuge test programmes, along with the procedures adopted for real-time signal conditioning and data recognition. The results of the field and centrifuge test programmes are discussed, and conclusions are drawn on the effectiveness of the compaction process, confirming the validity of the WAK test analysis in the prediction of improvement in soil stiffness with increasing number of blows.
An instrumented trial of vibro ground treatment supporting strip foundations in a variable fill
Authors: Watts K. S. , Johnson D. , Wood L. A. , Saadi A.
Published: October 2009

Full-scale instrumented load tests have been carried out to study the installation and performance of vibro stone columns supporting a strip foundation in a variable fill and the performance of a similar strip foundation on untreated ground. The results from site investigation and laboratory testing are presented, and the vibro design principles—in particular the use of a modification to a standard formula that reflects the radial densification of soil around the stone column—are outlined. The treated foundation performance is compared with predicted behaviour; calculated settlements are in reasonable agreement with measured values, but stress measurements suggest that current design assumptions significantly overestimate the degree of stress concentration on the stone columns. The degree of radial densification of fill around the stone columns varied according to installation technique and soil type. The implications of the trial observations for existing design methods are considered.
Analytical study of saturation effects on seismic vertical amplification of a soil layer
Authors: Yang J. , Sato T.
Published: October 2009

An analysis is presented of saturation effects on the amplification of a single soil layer to vertical earthquake excitation. Rigorous solutions for various responses are derived based on Biot's theory and the concept of homogeneous pore fluid. The transfer function of the layer is described as a function of degree of saturation, soil properties, layer thickness and loading frequency. Numerical examples are given to illustrate the influence of saturation on the motion amplification. The present study indicates that partial saturation of soils may always lead to a larger amplification compared with a full saturation model, and consequently provides a physical insight into an array observation on vertical site amplification during the Kobe earthquake of 1995.
Partially saturated tailings sand below the phreatic surface
Authors: Fourie A. B. , Hofmann B. A. , Mikula R. J. , Lord E. R. F. , Robertson P. K.
Published: October 2009

An opportunity to re–examine the liquefaction potential of hydraulically placed tailings sand has been provided by the Canadian Liquefaction Experiment (CANLEX). As part of this experiment, undisturbed samples of tailings sand were recovered after freezing the tailings in situ. Examination of undisturbed cores of frozen tailings sand clearly showed that the specimens were not fully saturated. This was confirmed by both physical measurements and laboratory tests in which gas was recovered from thawing specimens and analysed by gas chromatography. The gas was mainly air although a small amount of microbial gas was also present. Cryogenic scanning electron microscopy and confocal laser scanning microscopy were used to further confirm the existence of occluded gas bubbles. Triaxial undrained compression tests were carried out on undisturbed tailings specimens that were not back–saturated prior to shearing, in order to preserve the in–situ degree of saturation. Occluded air bubbles within the tailings sand, even if only in very small percentages by volume, are shown to have a marked effect on the response to undrained loading of the pore pressure within the tailings specimens. It is suggested that the liquefaction potential of tailings sand that could be expected to be contractive under undrained loading may be reduced by the occurrence of occluded gas bubbles within the voids. While it is not possible to quantify these effects accurately until further laboratory testing of both unsaturated and saturated loose tailings specimens has been conducted, this attribute could modify present engineering design. In this respect, obtaining undisturbed samples of granular soil is an important component of evaluating the liquefaction susceptibility of a specific deposit.
Sidere: numerical prediction of large-strain consolidation
Authors: Bartholomeeusen G. , Sills G. C. , Znidarčić D. , Van Kesteren W. , Merckelbach L. M. , Pyke R. , Carrier W. D. , Lin H. , Penumadu D. , Winterwerp H. , Masala S. , Chan D.
Published: October 2009

Large-strain consolidation theory is widely used for the management of dredged disposal sites. The theory is universally accepted to deal with this problem, though the determination of the material properties is not yet standardised. Decisions made on this level can lead to the prediction of a totally different consolidation history. This paper describes the results of a prediction exercise, performed using a batch of sediment from the river Schelde (Antwerpen, Belgium). Numerical modellers were given the data of four calibration experiments and were then asked to predict another experiment. Settling column experiments (0·2–0·6 m in height) with density and pore pressure measurements provided the basis for the calibration data. The prediction demonstrated the significance of the soil compressibility at low effective stresses, when time-dependent behaviour is observed.
Interactions between two rough spheres, water bridge and water vapour
Authors: Molenkamp F. , Nazemi A. H.
Published: October 2009

Micromechanical considerations of the interactions between the granular skeleton of an unsaturated granular soil and the contained moisture involve the classical interaction model consisting of a water bridge in contact with two rigid smooth spheres of equal radius, at a separation determined by their actual surface roughness, and surrounded by a gas with a vapour pressure at equilibrium with the water. In this paper the water volume and the interparticle contact force are related to the water suction, the water–solid surface contact angle, and the size and roughness of the spheres in dimensionless terms. The dimensionless water suction is also related to the corresponding relative humidity of the water vapour. The calculated equilibrium relations are shown to possess non-uniqueness, which is interpreted in terms of soil mechanical properties while recognising that for low saturations in natural processes the humidity of the pore air is the independent parameter. The developed analytical solutions show the classical toroidal approximation to be reasonable. These solutions are applied in a companion paper to clarify the concept of an intergranular stress induced by both pore suction and related surface tension.
Stability of seismically loaded slopes using limit analysis
Authors: Loukidis D. , Bandini P. , Salgado R.
Published: October 2009

Numerical limit analysis is used to assess the stability of slopes subjected to seismic loading. The soil is assumed to follow the Mohr–Coulomb failure criterion. The lower and upper bound theorems are formulated as linear problems to be solved using linear programming techniques. Based on finite element discretisation of the slope, the velocity field is optimised to find the lowest upper bound, and the stress field is optimised to obtain the highest lower bound. Limit equilibrium computations and log-spiral upper bound solutions were also performed for comparison purposes. Additionally, finite element analyses were done for selected cases. Results from the limit equilibrium and finite element methods are in excellent agreement with the rigorous lower and upper bounds for all cases studied. The slip surfaces obtained from both the limit equilibrium and log-spiral upper bound methods lie within the plastic zones obtained for the slopes from both finite element and numerical limit analysis. Plots are presented of the horizontal pseudo-static acceleration ratio kc = ac/g required to cause collapse of simple homogeneous slopes as a function of the slope inclination and shear strength parameters.
Modelling the osmosis effect on solute migration through porous media
Authors: Manassero M. , Dominijanni A.
Published: October 2009

In spite of an increasing number of publications that deal with the osmotic phenomenon that occurs within mineral barriers for pollutant control, the related models and their applications are not always correct, and they some times present inconsistencies between the initial assumptions and the results obtained. In order to investigate this topic thoroughly, a model has been proposed to describe the osmosis effect on solute migration within fine-grained porous media. This model is based on sound fundamental principles of thermodynamics, and complies with the basic physics postulates such as mass conservation and momentum balance. Its basic assumptions are incompressibility of the solid skeleton and the solvent, and infinite dilution of the solute. The osmotic phenomenon has been considered together with advective and diffusive one-dimensional transport of a bulk electrically neutral or uncharged solute under isothermal conditions, and the material constants of the governing differential equations are linked to the well-known parameters used in current geotechnical and chemical engineering practice. Therefore the proposed model can easily be used to assess the influence of the osmotic efficiency (ω) on the performances of mineral barriers for subsoil pollutant control, referring in particular to geosynthetic clay liners (GCL), whose behaviour, at low solute concentrations, can be considered very close to that of an ideal semi-permeable membrane. The proposed model has been tested using limit values of the input parameters in order to verify its consistency in terms of the physical meaning of the related outputs. The proposed theoretical approach has also been used to re-interpret some experimental data taken from specialised literature. The interpretation of the results, in terms of osmotic efficiency (ω), effective solute porosity (n*), bulk diffusion coefficient (D) and tortuosity factor (τ), seems to be intrinsically consistent and reliable. Nevertheless, the encouraging results of the proposed model require further ad hoc experimental tests in the laboratory before its definitive validation and calibration.
Evolution of shear bands in sand
Authors: Gudehus G. , Nübel K.
Published: October 2009

Localisation of deformation in narrow shear bands is a fundamental phenomenon of granular material behaviour. When modelling granular materials, shear localisation has therefore to be considered. The model must include an adequate constitutive law with an intrinsic length determining the thickness of the localised shear zones, and a representation of microscopic inhomogeneities triggering shear localisation. In the framework of a Cosserat continuum the behaviour of non-cemented granular material can be described by a hypoplastic law including the evolution of non-symmetric stresses and couple stresses. Void ratio fluctuations are introduced by a physically justified probability density function. The assumption is that fluctuations are minimal in the densest state, and maximal in the critical state. It is shown that shear bands can evolve spontaneously in the interior of a granular body even under homogeneous stress or displacement boundary conditions. Experimental verifications are given. Numerical results are compared with laboratory tests performed with a Cornforth and a Hamblytype biaxial apparatus. Shear localisation in the experiment is visualised by means of an optical method called particle image velocimetry. Further numerical results are compared with experimental results taken from publications.
Uplift capacity of rapidly loaded strip anchors in uniform strength clay
Authors: Thorne C. P. , Wang C. X. , Carter J. P.
Published: October 2009

The behaviour of horizontal strip anchors buried in clay is examined in this paper. A brief critique of the various approaches suggested for the design of these anchors is presented, with emphasis placed on estimation of the ultimate load that these anchors can withstand when loaded rapidly in uplift under undrained conditions. Possible mechanisms of failure are reviewed, including shear and tensile failure within the soil and the development of suction within the pore fluid, and the results of finite element predictions are compared with experimental data for ultimate loads. The analyses reveal that the behaviour of strip anchors in uplift is a function of the following non-dimensional parameters: H/B, γH/c and uc/c, where H is the depth of embedment of the anchor, B is the width of the strip anchor, γ is the unit weight of the soil, c is its undrained shear strength, and uc is the magnitude of the maximum tensile stress that can be sustained by the pore water in the soil. It is demonstrated that the ultimate uplift capacity is dependent on the availability of water at the surface of the soil and within the soil beneath the strip anchor. The analyses also show that shallow anchors in relatively strong soil tend to fail by the development of tensile failure in the soil above the anchor. The ultimate capacity of these shallow anchors is a function of the undrained shear strength of the soil, its self-weight and the tensile capacity of the pore fluid. By contrast, the failure mechanism for deeply buried anchors where the initial vertical total stress at the plate exceeds 7c involves only localised shear failure around the anchor, and as a result the ultimate capacity effectively becomes a function only of the undrained shear strength of the soil.
An experimental investigation of the mechanical behaviour of an unsaturated gneiss residual soil
Authors: Futai M. M. , Almeida M. S. S.
Published: October 2009

The paper presents compression and triaxial tests conducted under controlled suction in horizons B and C of a residual soil gneissic rock profile from south-east Brazil. Horizon B, found at the surface, consists of a 2 m thick reddish lateritic clayey soil layer, whereas horizon C is a saprolitic soil layer that reaches great depths. The block samples representing horizons B and C were manually taken from depths of 1 m and 5 m respectively. The test programme carried out consisted of isotropic and anisotropic compression tests as well as drained and constant water content triaxial tests. Tests were performed under saturated and unsaturated conditions at controlled suction. Strength parameters c and ϕ were shown to increase with matric suction. The critical state parameters were shown to vary with suction, which also expanded the yield curve. Data obtained may be useful for the development of soil constitutive models for unsaturated soils.
A clustered overlapping sphere algorithm to represent real particles in discrete element modelling
Authors: GARCIA X. , LATHAM J.-P. , XIANG J. , HARRISON J.P.
Published: October 2009

An algorithm is presented for representing irregular particles as clusters of overlapping spheres, for use within discrete element method (DEM) simulations of particulates. The algorithm is sufficiently fast to be implemented on desktop computers. Although volume and moment of inertia comparisons of resulting clusters with prototypical geometric data show that in the region of 50 to 100 spheres may be needed to represent a particle, actual DEM simulations of an unstable pile of simulated particles show that only 10 or so spheres may be sufficient to capture the mechanics of the system.
Effect of degree of hydration upon creep of mortars containing calcium lignosulphonate
Authors: Khalil S. M. , Ward M. A.
Published: October 2009

Synopsis

The influence of calcium lignosulphonate admixture upon the creep characteristics of two mortars, made with cements having different C3A contents, has been studied. The degree of hydration of the mixes at loading and throughout the loading period was the main parameter. For any mix, with or without admixture, the creep strain is the same for a given increase of hydration under load, provided that all the mixes are loaded at the same degree of hydration and the same stress-strength ratio. This suggests that the age at loading only affects creep in so far as it is related to the degree of hydration and development of strength. Creep after a certain time has two components: ‘non-hydrating creep’, which corresponds to the state of hydration at loading without further hydration under load, and ‘maturing creep’, which is related to the progress of hydration while under load.
Experimental investigation of the collapse of renforced concrete curved beams
Authors: Badawy H. E. I. , McMullen A. E. , Jordaan I. J.
Published: October 2009

Synopsis

The applicability of methods of plastic analysis to reinforced concrete curved beams is investigated and the results of experiments on seven straight and eight curved beams are presented. The straight beams were tested under different combinations of bending, torsion and shear, and the results are used to determine the intersection points of two yield surfaces (proposed in an earlier investigation) with the bending, torsion and shear axes and to check the validity of the surfaces. Of the curved beams tested, four were reinforced identically but were tested under different end conditions. In the other four, both the transverse reinforcement and the end conditions were varied so as to study changes in the mode of failure and the ultimate load. Comparison of the test results with the results predicted by the plastic analysis shows good agreement.
Influence of specimen geometry upon weight change and shrinkage of air-dried concrete specimens
Authors: Hobbs D. W.
Published: October 2009

Synopsis

Results are given of an investigation into the influence of specimen geometry and curing period upon the weight change and shrinkage of plain concrete specimens dried at 65% R.H. and 20°C. The concretes had water/cement ratios of 0·35, 0·47 and 0·59. It is shown that both specimen geometry and curing period have a marked influence upon weight change at all drying periods, and that shrinkage may be represented by the function f(At/V)t where A is the exposed surface area, V is the specimen volume and t is the drying period.
Structural idealization for deep beams with web openings
Authors: Kong F. K. , Sharp G. R.
Published: October 2009

Synopsis

The exact analysis of reinforced concrete deep beams with web openings presents formidable problems. However, the ultimate shear strengths of such beams can be predicted with reasonable accuracy by using a simple structural idealization. The idealization was based on pilot tests on 24 beams, but has now been checked against a further 32 tests covering a much wider range of web openings and web-reinforcement patterns. An improved shear strength equation is presented and design hints are given.
Limestone and siliceous aggregate concretes subjected to sulphuric acid attack
Authors: Hughes B. P. , Guest J. E.
Published: October 2009

Synopsis

The paper reports tests to determine the relative rates of erosion of siliceous-gravel and limestone-aggregate OPC concretes subjected to sulphuric acid concentrations of 0·0016% and 0.02% by weight. Care was taken to simulate conditions not too divorced from practice. The limestone-aggregate concrete eroded to present a relatively smooth surface with no detritus. In contrast, the siliceous-aggregate concrete eroded to form a very irregular surface with considerable aggregate detritus. The rates of erosion of the siliceous-aggregate concrete were very sensitive to the quality of the cement paste matrix, whereas the rates for the limestone-aggregate concrete were relatively insensitive. The behaviour of the limestone-aggregate concrete can be exploited in certain applications. There is no increasing surface roughness or accumulation of debris to reduce flow in channels, and damage with scrapers in sedimentation tanks can be minimized with a smoother surface. Design for erosion with limestone concretes entails estimating the thickness of a sacrificial layer of concrete appropriate for the rate of acid attack and the design life of the structure.
Detecting the progress of internal cracks in concrete by using embedded graphite rods
Authors: Lee N. K. , Mayfield B. , Snell C.
Published: October 2009

Synopsis

The observed shape of the concrete plug extracted in a pull-out test on a resin grouted block-ended bolt anchorage had previously suggested a theoretical failure model. The hypothesis proposed a two-part fracture mode with the lower, internal failure surface being of primary importance. The experiments described here were designed to test the proposal by using brittle electrical conductors to monitor the progress of the internal cracking.
Possible influence of small additions of pfa, gbfs and limestone flour upon expansion caused by the alkali–silica reaction
Authors: Hobbs D. W.
Published: October 2009

Synopsis

Experimental results are presented which show that replacing 5% by weight of Portland cement by four pulverized-fuel ashes, a ground granulated blastfurnace slag or a limestone flour has little effect upon the expansion of mortar bars tested at their critical alkali-reactive silica ratio.
Effect of sulphate content on the hydration and strength of cement/fly ashsystems with and without a water-reducing admixture
Authors: Haque M. N. , Ward M. A. , Langan B. W.
Published: October 2009

Synopsis

Earlier studies of the optimum SO3, contents of cements in the presence of chemical admixtures have been extended to mixes containing cement (both OPC and SRPC), sub-bituminous high-lime fly ash and water-reducing admixture. The hydration character istics have been studied by means of conduction calor imetry; and measurements of the compressive strength of mortars up to 56 days have been used to assess optimum SO3, contents. The optimum SO3, content of the plain cement mixes in the presence of the admixture was 1% higher than the as-received cement. The optimum SO3, content of the cement/fly ash/admixture mixes was found to be close to that of the as-received cements, It is suggested that, where large volumes of a concrete containingjy ash and admixture are to be produced, it may he worthwhile determining the optimum SO3, con tent of the particular mix, to assess whether adjusting the SO3, content of the mix at the batching plant may be cost and energy-efective.
Three-dimensional stress distribution in concrete masonry prisms and walls
Authors: Khalil M. R. A. , Shrive N. G. , Ameny P.
Published: October 2009

Synopsis

Three-dimensional finite element analysis is used to study the stress distribution at working stress levels in masonry constructed of hollow concrete blocks. The stress analysis is performed on models of ungrouted and grouted concrete block prisms and walls. The effects of the following factors are examined: grouting, mortaring style, capping, platen restraint, shell taper of concrete blocks, core alignment of walls constructed in running bond, and mortar stiffness. The stress patterns are used to evaluate the validity of certain masonry failure theories.

The stress distribution in a running-bond wall, where the cores of the blocks do not align vertically, is found to be significantly different from the distribution in a stack-bonded prism. Substantial improvement in the performance of walls in running bond is attainable if the cores are aligned and the taper of the core is made as small as practicable.
Effects of embedded reinforcement on measured strength of concrete cylinders
Authors: Loo Y. H. , Tan C. W. , Tam C. T.
Published: October 2009

The effects of embedded steel bars on the strength of concrete cylinders as affected by various parameters were investigated. These parameters were the size and the length/diameter ratio of the cylinders, the positioning of the steel bar, the bar size and the cube strength of concrete. For a length/diameter ratio of 1·0, the experimental results differed significantly from the calculated values based on the correction formula recommended in BS 1881, Part 120. The inclusion of steel up to 4% by volume in 100 mm × 100 mm cylinders did not have any detrimental effect, but for deformed high tensile steel bars of 13–20 mm diameter, increases of up to 9% in the measured strengths over those of the control specimens were observed.
Creep of high–strength concrete and normal–strength concrete
Authors: Marzouk H.
Published: October 2009

The development and use of high–strength concrete has been evolutionary. High–strength concrete is used for tall buildings, bridges, long–span structures and offshore platforms. Very little information is available on the creep of high–strength concrete compared with that of normal concrete at room and low temperatures. Test results are presented of creep strains at room temperature of high–strength concrete (70 Mpa) and normal concrete (40 MPa) subjected to stresses of 25, 50 and 75% of their 28 day strength for one year. Also provided are creep results of test specimens exposed to temperatures of 20, 0 and — 10°C for 91 days. In general, creep strains of high–strength concrete are smaller than those of normal concrete at all corresponding stress/strength ratios. The relation of creep to stress–strength ratio at room temperature was found to be linear for the two grades of concrete. Test results revealed that low temperatures had a minor effect on the magnitude of creep strains for both types of concrete. The creep mechanism of high–strength and normal concrete can be explained mainly by the diffusion of absorbed moisture, while at low temperatures both the gel deformation and absorbed moisture diffusion can cause a large change in the energy of the system, and accordingly creep strains were slightly increased.