bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of a sample containing a shear surface from a recent landslip, south Cotswolds, UK
Authors: Anson R. W. W. , Hawkins A. B. 
Published: October 2009

The paper reports analysis of a block sample taken from a trial pit, hand dug across the shear surface of an active landslide in the south Cotswolds. The slide is located on the Upper Fuller's Earth, some 50m downslope of the overlying Great Oolite limestone, the weathering of which has produced ooliths and gravel-sized fragments which are incorporated within the slipped mass. Sampling at 5 mm intervals confirmed the inverse relationship between the natural moisture content and calcite content. In order to assess the significance of changes in moisture content in the fine fraction, the influence of the non-sorptive calcite was removed and a normalized moisture content profile established. Examination of the lower shear surface using scanning electron microscopy confirmed the parallel orientation of the clay minerals for a thickness of some 1 μm. This thin veneer extended over areas of granular material, highlighting the importance of obtaining representative samples when shear strength assessment is undertaken. Le papier rend compte de 1'analyse d'un échantillon de bloc prélevé dans un pmts d'exploration creusée à la main à travers la surface de cisaillement d'un glissement de terrain actif dans le sud des Cotswolds. Le glissement est situé sur la terre à foulon supérieure, é quelque 50 m en contrebas du calcaire oolithique (Great Oolite) sus-jacent; dont l'altération a produit des oolithes et des fragments de la taille de gravillons incorporés dans la masse glissée. Les prélèvements d'échantillons, à intervalles de 5 mm, ont confirmé la relation inversement pro-portionelle entre la teneur en eau naturelle et la teneur en calcite. Pour pouvoir évaluer l'importance des changements de la teneur en eau dans la fraction fine, on a éliminé l'influence de la calcite non adsorbante et établi un profil de teneur en eau normalisé. L'examen de la surface de cisaillement inférieure par microscopie électronique à balayage, a confirmé l'orientation paralléle des minéraux d'argile sur une épaisseur de quelque 1 μm. Cette fine couche s'étendait sur les zones de matériaux granulaires, soulignant ainsi l'importance de l'obtention d'échantillons représentatifs lorsqu'on étudie la résistance au cisaillement.
Assessing a soft soil tunnelling numerical model using field data
Authors: Bernat S. , Cambou B. , Dubois P. 
Published: October 2009

The aim of this paper is to assess a numerical soft soil tunnelling model, using field data. The lining of the tunnel to be studied was a fairly thick, very rigid structure. Given the low level of applied stresses, lining deformation was slight, and the deformation around the tunnel essentially concerned the annular space created between the soil and the lining during tunnelling. This void was partially filled with injected grout. The primary purpose of this paper is to examine models that demonstrate soil–tunnelling interactions. An empirical ‘deconfinement factor λ’ is then used to represent stress reduction around tunnels during construction. In the first model it is simply assumed that soil stresses around the tunnel reduce linearly by a factor λ. The second analysis refines this notion and considers a temporary 'reconfinement' stage in order to represent both the grouting behind the lining once it is installed, and the hydrostatic pressure that acts on the impervious tunnel (pushing the lining up into the grout). Comparisons between these models and field data measurements obtained in three fully instrumented areas of the Lyons-Vaise metro site will be discussed. Cet article a pour but d'évaluer un modèle numérique pour la construction d'un tunnel dans un sol meuble, en utilisant des données de terrain. Le revêtement du tunnel à étudier était une structure assez épaisse et très rigide. Étant donné que les contraintes appliquées étaient faibles, la déformation du revêtement était 1égère et la déformation autour du tunnel était liée essentiellement a l;espace annulaire créé entre le sol et la paroi pendant la construction. Ce vide était partiellement rempli de coulis injecté. Cet article a pour objet, principalement, d'examiner les modèles qui montrent les interactions entre le sol et l;action de creusement du tunnel. Nous utilisons ensuite un ‘facteur de d6confinement λ, obtenu de mamère empirique, pour représenter la baisse de contrainte autour des tunnels pendant la construction. Dans le premier modèle, nous présumons simplement que les contraintes dans le sol autour du tunnel baissent de fa¸on linéaire d'un facteur λ. La seconde analyse raffine cette notion et considère une étape de ‘re-confinement’ temporaire afin de représenter à la fois l'injection de coulis derrière la paroi une fois que celle-ci est installée et la pression hydrostatique qui agit sur le tunnel étanche (déplacement vertical du revetement à l'intéreur du coulis). Nous ommentons la comparaison entre ces modèles et les mesures obtenues sur le terrain dans trois zones entièrement instrumentées sur le site du métro de Lyon-Vaise.
Rigorous plasticity solutions for the bearing capacity of two-layered clays
Authors: Merifield R. S. , Sloan S. W. , Yu H. S. 
Published: October 2009

This paper applies numerical limit analysis to evaluate the undrained bearing capacity of a rigid surface footing resting on a two-layer clay deposit. Rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity. Both methods assume a perfectly plastic soil model with a Tresca yield criterion and generate large linear programming problems. The solution to the lower bound linear programming problem is obtained by modelling a statically admissible stress field, whereas the upper bound problem is solved through modelling a kinematically admissible velocity field. Results from the limit theorems typically bracket the true collapse load to within approximately 12%, and have been presented in the form of bearing capacity factors based on various layer properties and geometries. A comparison is made between existing limit analysis, empirical and semi-empirical solutions. This indicates that the latter can overestimate or underestimate the bearing capacity by as much as 20% for certain problem geometries. Dans cet exposé, nous servons d'analyses limites numériques pour évaluer la capacité porteuse non drainée d'une assise à surface rigide reposant dur un dépöt argileux à deux couches. On obtient des limites rigoureuses pour la capacité porteuse ultime en employant des é1éments finis en conjonction avec les théorèmes de limite à borne supérieure et inférieure de la plasdcité classique. Les deux méthodes supposent un modéle de sol parfaitement plastique avec un critère d'élasdcité Tresca et entraïnent de gros problèmes de programmation linéaire. On obtient la solution au problème de programmation linéaire de limite inférieure en faisant la maquette d'un champ de contrainte admissible en statistique tandis que le problème de limite supérieure est résolu par la mise en maquette d'un champ de vélocité admissible en cinétique. De manière typique, les résultats de théorèmes limites cernent dans une marge d'environ 12% la vraie charge d'affaissement et sont présentés sous forme de facteurs de capacité porteuse basés sur les propriétés et géométries des diverses couches. Nous comparons les analyses limites existantes, les solutions empiriques et les solutions semiempiriques. Cette comparaison indique que ces dernières peuvent surévaluer ou sousestimer de 20% la capacité porteuse dans le cas de certaines géométries à problème.
A micromechanics-based methodology for evaluating the fabric of granular material
Authors: Pan Y. -W. , Dong J. -J. 
Published: October 2009

A micromechanics approach can successfully model the stress–strain–strength relation of a granular material once the microcharacteristics of the material have been obtained. However, it is usually difficulty to determine the fabric of natural granular materials. Using a stress-dependent micromechanics model, the elastic properties can become a function of the geometric and kinetic fabric. Also, the wave velocity can be related to the elastic properties. Consequently, this paper proposes a methodology for evaluating the fabric of a granular assembly from a set of measured wave velocities. The methodology contains three elements: (a) a stress-dependent micromechanics elastic model, (b) an anisotropic elastic wave propagation theory and (c) an optimization procedure. It is verified by calibrating available wave velocity data of a glass assembly and washed mortar sand. The methodology is further applied to study the microstructural evolution of the washed mortar sand under biaxial stresses. Two aspects of fabric change can be observed: (a) concentration of contact normals in the major principal direction and (b) a residual fabric after subsequent loading/unloading. Une approche micromécanique permet de faire une maquette de la relation tension-allongementrésistance ďun matériau granulaire une fois que ses micro caractérisdques ont W obtenues. Cependant, il est habituellement difficie de déterminer la structure des matériaux granulaires naturels. Si ľon utilise une maquette micromécanique tributaire de la tension, les propr!étés élastiques peuvent devenir fonction de la structure géométrique et cinédque. De plus, la vitesse des ondes pent Être apparentée aux propriétés é1astiques. C'est pourquoi, dans cette étude, nous proposons une méthodologie permettant ďévaluer la structure &caorn;un assemblage granulaire à partir &acorn;un lot de vitesses ďondes mesurées. La méthodologie contient trois éléments: (a) une maquette élastique micromécanique tributaire de la tension, (b) une théorie de propagation des ondes élastiques et anisotropes et (c) une procé& dure ďoptimisation. Nous vérifions en les calibrant les données disponibles sur les vitesses ďondes ďun assemblage de boule de verre et ďun sable de morder lavé La méthodologie sert ensuite à étudier ľévolution microstructurale du sable de morder lavé soumis à des tensions biaxiales. On observe alors deux genres de changements de structure: (a) une concentration des perpendiculaires de contact dans la direction majeure principale et (b) une structure résiduelle aprés des charges/décharges consécutives.
Intergranular state variables and stress–strain behaviour of silty sands
Authors: Thevanayagam S. , Mohan S. 
Published: October 2009

Relative contributions by the coarser and finer grains in a silty sand to its stress–strain response are affected by the intergranular matrix structure. The nature of this contribution is illustrated using an intergranular matrix phase diagram in terms of void ratio (e), fines content (FC), and intergranular and interfine void ratios (es and ef). New intergranular state parameters (ψs, ψf) and (es, ef) are introduced as state variables to characterize silty sands; es and ef dictate the steady-state characteristics of silty sand at low and high fines contents, respectively; ψs and ψf reflect the plastic compressibility characteristics at low and high fines contents, respectively. Using these state variables, the anticipated stress–strain–strength behaviour of silty sand in comparison to that of the host sand is presented. Similar stress-strain behaviour is expected at the same es and initial confining stress σ′c, with a few exceptions. At a constant void ratio e, es increases while ef decreases with addition of fines; a silty sand passes through different states. First, at low fines content, es (< emax,HS, the maximum void ratio of the host sand, case 1), and high ef the stress–strain behaviour is primarily governed by intergranular friction between the coarser grains. The steady-state line (SSL) is primarily dependent on es and is fairly independent of σ′c; When compared at the same es and at the same σ′c(or at the same ψ or ψs), the silty sand and the host sand show similar (not identical) stress–strain behaviour; with addition of fines, as es increases, the collapse potential increases and the stress–strain response becomes weaker. Second, with further addition of fines, when es approaches or exceeds emax,HS, the SSL is influenced by es and σ′c. When es is near emax,HS (case 2), the stress–strain curves for silty sands are similar at the same es and the same σ′c (or at the same ψ or ψs), but different from and stronger than that of the host sand. At very loose states (es > emax,HS; case 3), the stress–strain curves, normalized with respect to σ′c, are similar at the same es (or at the same ψ or ψs). Third, with further addition of fines beyond a threshold value, ef becomes sufficiently low (case 4); the fines impart a significant influence, while the role of intergranular (coarser-grain) friction diminishes; the silty sand is expected to behave similarly (not identical) to the host fines at the same ef and ψf ; at this stage, with further addition of fines, the collapse potential decreases.
Collapse load of deep reinforced concrete beams
Authors: Kumar Prabhat 
Published: October 2009

Synopsis A truss model is analysed to estimate the collapse load of a deep beam with a shear-span|effective-depth ratio of less than 1·0. The expressions for collapse load in the flexural and shear-proper modes of failure, as well as expressions for the value of the reinforcement ratio separating them are derived and verged against the available test results. Good agreement is found. An analysis of the beams containing web reinforcement is also presented and verified against the available test results with good agreement. Finally the design of deep beams in practice is considered and a design example is given.
Creep, shrinkage and elastic strain in concrete bridges in the United Kingdom, 1963–71
Authors: Tyler R. G. 
Published: October 2009

Synopsis Long-term creep and shrinkage measurements carried out on concrete bridges in England in the period 1963–71 are summarized. The concretes used were mainly of the 50 N/mm2 class. Typically, on the full scale, shrinkage was shown to be about 200 × 10−6 and the creep factor, defined as the ratio of creep to elastic strain to time infinity at the centroid of a prestressed concrete member for a decaying prestressing force, to be about 2·0. The most likely cause of cracking soon after casting was shown to be the early-age thermal movement caused by the hydration of the cement. Results show that creep and shrinkage usually increase linearly with the logarithm of time, with cyclic seasonal variations. The effect of the seasons upon the calculation of movements is discussed.
The strain capacity of compression-zone concrete subjected to short-term loading
Authors: Phipps M. E. 
Published: October 2009

Synopsis Values and distribution of concrete compression strain from prism and structural member tests have been reported by many investigators. Much of the information indicates that strain measurements in concrete are irregular and unpredictable. In this paper, tests are described which show that, for eccentrically loaded plain concrete prisms, the surface compression strain over the length of the failure zone can be assessed to within ± 20%. This strain is shown to be dependent upon the depth to the neutral surface and the depth of any tension concrete adjacent to the compression concrete. The length of the compression failure zone is related to the depth to the neutral surface, but does not appear to be affected by adjacent tension concrete. In studying the effects of different depths of compression and tension concrete, a theory of failure for concrete in compression was evolved. This theory suggests that the strain capacity of concrete in compression, and so the deformation capacity of structural concrete in general, is dimension- or size-dependent.
The disintegration of concrete containing sulphate-contaminated aggregates
Authors: Samarai Mufid A. 
Published: October 2009

Synopsis Problems related to concreting in the Middle East and similar localities have renewed interest recently in the disintegrating effect of sulphate-contaminated aggregates. The paper describes a research programme initiated to study the influence of sulphate-contaminated fine aggregates upon the strength and volume changes of cement mortars. Experimental details are given of tests carried out on more than three thousand specimens. Factors such as type of cement, sulphate content and tricalcium aluminates were fully studied. Allowable limits for the SO3 content that can be incorporated into the concrete without adversely affecting its properties were established.
Ultrasonic assessment of concrete strength at early ages
Authors: Elvery R. H. , Ibrahim L. A. M. 
Published: October 2009

Synopsis This paper describes tests carried out to examine the relationship between ultrasonic pulse velocity and cube strength of concrete from ages of about 3 h over a curing temperature range from 1 to 60°C. It is found that this relationship is practically independent of water/cement ratio and temperature but influenced by both aggregate content and type of cement. Strength estimation from pulse velocity was found to be less reliable for velocities less than about 2 km/s than it is for higher velocities. Prediction of 28 day cube strength from early-age pulse velocity is possible with some limitations, particularly with regard to temperature effects.
A study of the applicability to the fatigue of concrete of the Palmgren-Miner partial damage hypothesis
Authors: Tepfers Ralejs , Fridén Claes , Georgsson Leif 
Published: October 2009

Synopsis This investigation provides some information concerning the applicability to the fatigue of concrete of the Palmgren-Miner partial damage hypothesis. The results do not contradict this hypothesis. The tests were performed on small concrete cylinders at high load-alternation frequencies. A Wöhler curve plotted for the concrete cylinders shows that fatigue in these occurs in the same way as in large specimens subjected to lower load-alternation frequencies. Fatigue of concrete due to non-alternating variable load pulses can be calculated from an expression relating to the Wöhler curve for concrete, combined with the Palmgren-Miner partial damage hypothesis.
Tests on concrete beams with mixed types of reinforcement
Authors: Taylor R. , Mills P. E. , Rankin R. I. 
Published: October 2009

Synopsis Tests are reported on twenty-five concrete beams in which the reinforcement at the soffit of each beam consisted of a combination of a structural steel channel and very-high-strength reinforcement. In some cases, this very-high-strength reinforcement took the form of prestressing strand. The tests fall into two parts, one relating to the flexural strength of the beams, the other relating to their shear strength. In all cases, the behaviour of the beams was similar to that of normal reinforced concrete. For the beams failing in flexure, it was found that the strain-compatibility method of calculation in CP 110 predicted the failure load quite accurately, even though stresses in the reinforcement attained values up to three times the maximum at present permitted in the code of practice. The beams failing in shear were somewhat stronger than the requirements for shear in CP 110 would suggest.
Compressive strength and ultimate strain of concrete under impact loading
Authors: Hughes B. P. , Watson A. J. 
Published: October 2009

SYNOPSIS A drop-hammer test has been used to measure the compressive strength, ultimate strain, energy absorption and deformation modulus of concrete cubes under impact loading. By assuming a trapezoidal function for both the hammer impact pulse and the cube impedance function, hypothetical load and strain records have been derived which are similar to the initial experimental records measured on an oscilloscope. Concretes with varying mix proportions and two different coarse aggregates were examined and the results for compressive strength and ultimate strain are reported.
Deformation and fracture of plain concrete
Authors: Lowe P. G. 
Published: October 2009

SYNOPSIS Despite a great volume of investigation of the deformation and fracture of concrete, there appears to be no coherent model available to explain the observations. In this paper there is attempted an explanation of the available experimental data derived from 'triaxial' testing of concretes in terms of a theory of simple elastic deformation and tensile strain fracture. It is argued that there is sufficiently good agreement between theory and a number of the prominent features of the experimental data to warrant further investigation and elaboration of the general theme of strain rather than stress limitation as the primary feature of concrete fracture behaviour.
A mathematical description of the deformational behaviour of concrete under complex loading
Authors: Kotsovos M. D. , Newman J. B. 
Published: October 2009

Synopsis A mathematical description of the deformational behaviour of concrete under any type of short-term static loading is developed, using a model material with the same strength characteristics. The mechanical properties of the model are defined by analysing experimental data obtained at Imperial College from tests on concrete under various states of multiaxial stress. The testing techniques used have been validated by comparing the results obtained with those produced by other institutions investigating the behaviour of concrete under similar stress conditions but with different apparatus. In the analysis, each stress and strain state is resolved into a hydrostatic and a deviatoric component and it is assumed that any non-linear material behaviour is dictated mainly by fracture processes occurring under increasing stress.
Further development of the two-point test for workability and extension of its range
Authors: Tattersall G. H. , Bloomer S. J. 
Published: October 2009

Synopsis Apparatus has been developed to measure the flow curve of concretes of medium to high workability. An impeller in the form of an interrupted helix is rotated uniaxially in the concrete by means of a hydraulic transmission and the torque is determined from measurement of the oil pressure. The flow curves conform closely to the Bingham model and, by suitable calibration, it is possible to express values of yield stress and plastic viscosity in fundamental units.
The effect of aggregate concentration upon the strength and modulus of elasticity of concrete
Authors: Stock A. F. , Hannantt D. J. , Williams R. I. T. 
Published: October 2009

Synopsis The paper presents details of art investigation into the effect of aggregate concentration upon the strength and modulus of elasticity of concrete in both uniaxial tension and uniaxial compression. The test results relate to cement paste and to mixes containing 20 to 80% by volume of a graded aggregate. Emphasis was placed on accurate determination of the specific gravity and absorption of the constituent aggregate size fractions in an attempt to maintain a constant free water Icement ratio in the various mixes. The specimens were continuously rotated during the setting period in order to minimize settlement of the aggregate particles. The results suggest that the strength of cement paste in tension and in compression is reduced by the addition of 20% by volume of graded aggregate, falling to a minimum value at a volume fraction of 30 to 35% and then increasing with further addition of aggregate. In contrast, the modulus in tension and in compression increases with the addition of aggregate and the measured values are compared with theoretical predictions based upon the laws of mixtures.