bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of cement concrete with mineral admixtures
Authors: Bapat J. D.
Published: October 2009

The scope of manufacturing blended cements in India and the resultant saving in energy consumption were identified. The characterisation of the two main mineral admixtures, namely fly ash (FA) and blast furnace slag (BFS), was based on their chemical and mineralogical composition and their particle characteristics. It was found that all the three factors are important from the point of view of selection of appropriate mineral admixture for blending with cement. The durability performance of concrete with blended cements was improved in terms of its resistance to the three deteriorating factors, namely alkali±silica reaction (ASR), sulphate attack and the corrosion of steel reinforcement. The improved resistance towards the ASR was due to the higher retention of alkalis and the refinement of pore structure, and is due to formation of secondary calcium silicate hydrate (C-SH) during the hydration of FA or BFS components in cement. Its resistance towards the Na2SO4 expansion is on account of lower content of free Ca(OH)2, besides the refinement of pore structure. Its lower resistance towards the strength reduction in MgSO4 environment, like ordinary portland cement (PC), is attributed to the deleterious reaction of Mg++ cations with C-S-H. In general, blended cements having tricalcium aluminate (C3A) contents in the range of 5–8% and the FA content of 25–30% or the BFS content above 60%, show moderate to good sulphate resistance. The higher corrosion resistance is attributed to the refinement of pore structure resulting in lower chloride and oxygen diffusivity, greater chloride binding capacity and higher electrical resistivity of the concrete made with blended cements. In comparison to concrete with OPC only, early and extended curing are required to obtain higher long term strength and better durability performance: the economic considerations show that the use of blended cement in concrete is the cheapest alternative available to control reinforcement corrosion.
Measurement of porosity as a predictor of the durability performance of concrete with and without condensed silica fume
Authors: Claisse P. A. , Cabrera J. G. , Hunt D. N.
Published: October 2009

The objective of this article is to investigate the use of porosity as a predictor of the properties of concrete that control its durability. In particular concretes containing silica fume (SF) have been investigated. Four different mixes were made, two containing SF and two control mixes without SF. The mixes were tested using three different curing conditions and three different test ages. The porosity was measured with helium intrusion, mercury intrusion and by calculation from weight loss observations. A wide range of durability related properties were measured and the results correlated with the porosities. It is concluded that the porosity is an excellent predictor for the transport properties but less good for actual corrosion rates. It is also indicated that models developed for concretes without SF should be used with great caution for SF concretes.
Reaction of rice husk ash with OPC and portlandite
Authors: Ordóñez L. M. , Payá J. , Coats A. M. , Glasser F. P.
Published: October 2009

Sandwiches made of pelleted rice husk ash (RHA) and an OPC/hydrated lime mixture were immersed in distilled water for 7 and 28 days at 25° and 40 ± 1°C to study interdiffusion occurring during pozzolanic reaction. For this purpose BSE microphotographs and chemical image maps for Si, Ca, K, Na, Fe, Al and S were made across the reaction interface of pellets. Furthermore, porosities of RHA pellets were determined. BSE and Ca maps show the formation of a reaction product layer within the space formerly occupied by RHA. This layer is composed of C-S-H and is thicker in RHA/hydrated lime (125–150 μm) than in RHA/OPC (20–40 μm) pellets after 7 days. Its thickness does not much increase after 7 days. In a fixed time, reaction extends to greater depth at 20°C than 40°C, indicating that the pozzolanic reaction rate is not accelerated by temperature in this range.
Prediction of cement paste pore water pressure variations during setting period
Authors: Amziane S. , Andriamanantsilavo N.
Published: October 2009

Results from tests,using 1–10 m formworks, conducted to examine the evolution of pore water pressure in a fresh cement paste during setting are presented. Experiments reveal that, from the initial state up to cancellation, profiles of both pore water pressure and total lateral pressure are hydrostatic. Simultaneously, the evolution kinetics of both pressures are identical. Consequently, the variation of the lateral pressure envelope during setting is modelled using the Richards equation. Modelling requires the identification of two parameters (permeability of the fresh cement paste and a source term) that describe water requirements during setting. The permeability coefficient is examined through a drainage experiment, coupled to the inverse analysis for identification of the coefficients resulting from the solution of the Richard's equation. Using the parameters identified, the results of the numerical simulation of the pressure variations into the formwork, are in good agreement with the experiment.
Non-contact resistivity measurement for characterisation of the hydration process of cement-paste with excess alkali
Authors: He Z. , Li Z. J.
Published: October 2009

A non-contacting electrical resistivity measurement device was used to investigate the influence of excess alkali on the hydration process of cement paste. The experiment was conducted with several specimens with different water/cement ratios and alkali contents. It was found that the resistivity curves measured using the method can be used to identify different hydration stages, such as dissolving period, competition period, setting period and hardening period. To verify the results of the resistivity measurement, hydration heat rates of cement pastes were measured using a JAF calorimeter. It was found that the resistivity curve and the curve of heat evolution rate of cement were closely related and thus can be used to examine a hydration process. The study showed that the hydration process of a cement paste could be influenced significantly by alkali content and caution must be exercised to control its influence on the early age properties of cement-based materials.
Exploratory data analysis of trace elements in clinker
Authors: Abonyi J. , Tamás F. D. , Tritthart J.
Published: October 2009

Analysis of trace element measurement data from clinker may lead to insights into raw material properties and could be used to solve practical problems, namely to determine the origin of the clinker (i.e. the manufacturing works). For this purpose, several hundred clinkers from nine countries were analysed by replicated quarterly samples to determine their Mg, Sr, Ba, Mn, Ti, Zr, Zn and V contents. This paper presents a survey of simple exploratory data analysis procedures that have been found to be particularly useful in the qualitative analysis of clinker trace element contents. Data presentation box and quantile-quantile plots are proposed and used to analyse the relationships between different factories and different trace elements.
Canal reservoirs in Great Britain
Authors: Brown David Henthorn
Published: October 2009

This paper considers the development of canal reservoirs in Great Britain from a historical perspective and reflects how they developed in the light of changing requirements and engineering advances. Ninety-two reservoirs, with an average age of 188 years, remain the responsibility of British Waterways. There are many more which have found other uses or been discontinued.
History of high-alumina cement. Part 2: Background to issues
Authors: Neville A.
Published: October 2009

Part I of this paper (Engineering History and Heritage, 2009) dealt with the Stone Committee Report as a solution to the problem of failure of HAC Concrete in structures. This part discusses the reasons why the problems arose: in a nutshell, ignorance of the behaviour of HAC and relentless pressure to sell HAC as a problem-free material.
Model studies of ring foundations on geogrid-reinforced sand
Authors: Laman M. , Yildiz A.
Published: October 2009

An experimental investigation into the ultimate bearing capacity of ring foundations supported by a sand bed with and without geogrid reinforcement is reported. The parameters investigated are optimum ring width, the effect of depth of first reinforcement, the number of reinforcement layers, and the effect of reinforcement layer length on the ultimate bearing capacity of ring foundations. The results of the experimental study proved that the reinforcement had a considerable effect on the ultimate bearing capacity of the ring foundations. It was also proved that ultimate bearing capacity values can, depending on the reinforcement geogrid arrangement, be improved by up to three times that of the unreinforced case. It was shown that a ring foundation with the optimum width showed similar performance to that of full circular foundation with the same outer diameter on the ring foundations for both the unreinforced and reinforced cases.
Use of the inclined plane test in measuring geosynthetic interface friction relationship
Authors: Reyes Ramirez R. , Gourc J. P.
Published: October 2009

The inclined plane test is commonly used when studying the stability of sloping geosynthetic liner systems under conditions of low normal stress. Emphasis is placed on analysis of the initial sliding phase in a standard test, prior to reaching the non-stabilised sliding phase, which is generally disregarded by designers. Comparative tests for two different geomembrane materials reveal that it is possible to clearly distinguish different interface behaviours under field conditions. Subsequently, two new test procedures using the inclined plane device are proposed: a creep test that could lead to reconsidering the significance of the threshold angle of friction, ϕgg, determined from a standard inclined plane test; and an abrasion test that could be used when studying geosynthetic slope stability in the field, in order to take into account the geosynthetic laying conditions.
FEM simulation of the failure of reinforced sand slopes subjected to footing load
Authors: Kotake N. , Tatsuoka F. , Tanaka T. , Siddiquee M. S. A. , Huang C.-C.
Published: October 2009

The results from a series of laboratory model tests on unreinforced sand slopes and those reinforced with reinforcing strips that were brought to bearing capacity failure by vertical and central loading using a rigid strip footing placed on the slope crest were simulated numerically by the FEM. In the FEM analysis, the effects of the following factors were taken into account: (a) confining pressure; (b) anisotropy; (c) non-linear pre-peak strain-hardening and strain-softening; (d) dilatancy; and (e) strain localisation into a shear band or bands having a thickness in proportional to the particle size. The FEM simulation for both unreinforced and reinforced sand slopes was generally in good agreement with the physical experimental results with respect to the load–settlement relationships, the strain fields showing failure modes, and the distributions of reinforcement tensile force for the different reinforcement arrangements examined. The stress fields from the FEM analysis are also presented.
Liquid flow equations for drainage systems composed of two layers including a geocomposite
Authors: Giroud J. P. , Zhao A. , Tomlinson H. M. , Zornberg J. G.
Published: October 2009

The focus of this paper is on applications (e.g. some leachate collection layers in landfills) where a drainage system consists of a geocomposite overlain by a sand layer. If the geocomposite does not have sufficient flow capacity to convey all the collected liquid, a fraction of the liquid flows in the sand layer. In such drainage systems, the maximum liquid thickness should be calculated to check that the flow capacity of the sand is not exceeded, and the maximum head should be calculated to check that it is less than the maximum head prescribed by regulations. This paper presents a method for calculating the maximum liquid thickness and the maximum head in drainage systems composed of two layers, with the lower layer being a geocomposite. Equations give the maximum liquid thickness and the maximum head as a function of the rate of liquid supply, the hydraulic conductivities of the two layers, the length of the drainage system, and the slope. Design examples are presented.
State-of-the-art report: GCL shear strength and its measurement
Authors: Fox P. J. , Stark T. D.
Published: October 2009

This paper presents a comprehensive source of information on the shear strength and shear strength testing of geosynthetic clay liners (GCLs). Essential concepts of shear stress–displacement behavior and shear strength interpretation are presented, including long-term performance issues, followed by detailed discussions on the laboratory measurement of the shear strength of GCLs and GCL interfaces. The paper also provides recommendations for the selection of design failure envelopes for stability analyses and checklists to assist users in the specification of GCL shear testing programs. North American practice is emphasized and discussions are focused primarily within the context of landfill bottom liner and cover systems. Conclusions are drawn with regard to GCL shear strength behavior and current GCL strength testing practice, improvements for GCL strength testing and reporting are suggested, and future research needs are identified.
Low-temperature air channel testing of thermally bonded PVC geomembrane seams
Authors: Stark T. D. , Choi H. , Thomas R. W.
Published: October 2009

The objective of this paper is to develop a procedure for air channel testing of dual-track thermal seams at low sheet temperatures and recommendations for reducing destructive testing of field PVC geomembrane seams. This objective is accomplished by developing relationships between seam peel strength and seam burst pressure for sheet temperatures ranging from 0.6°C to 25.6°C during field air channel testing. This paper refines the original correlation presented by Thomas et al. using data for low sheet temperatures, and develops a polynomial equation that can be used to convert the sheet temperature during field air channel testing to the air channel pressure required to satisfy the specified seam peel strength instead of graphically finding the air channel pressure from an Arrhenius analysis. Thus the proposed relationship and equation allow the seam peel strength to be determined from the field air channel testing without conducting destructive tests.
Seismic stability of a reinforced-soil structure constructed after the mid-Niigata prefecture earthquake
Authors: Shinoda M. , Watanabe K. , Kojima K. , Tateyama M. , Horii K.
Published: October 2009

ABSTRACT: The mid-Niigata prefecture earthquake in 2004 damaged a number of structures, including embankments, earth slopes and retaining walls. This paper describes a selected collapsed earth slope constructed in a valley eroded by the Shinano River with low-permeability backfill soil. The failure mechanism of the earth slope is shown by the high response acceleration at the crest owing to the low stiffness and strength of the backfill soil. The paper also describes numerical techniques to evaluate the performance of the structure constructed before and after the earthquake. For the selected earth slope, the response acceleration during the earthquake and the groundwater level before the earthquake were estimated by finite element (FE) analysis. Deformation analysis was conducted using Newmark's sliding-block analysis, which implements the estimated groundwater level and response acceleration of the structure subjected to the earthquake by the above FE analysis. According to the results of the numerical analysis, it is important for geosynthetic reinforcement to increase the stiffness of the reinforced soil to allow for a decrease in the deformation at the crest of the structure. The numerical analysis in this study revealed that the performance of the reinforced retaining wall constructed after the earthquake is significantly better than that of the collapsed earth slope constructed before the earthquake.
A new type of integral bridge comprising geosynthetic-reinforced soil walls
Authors: Tatsuoka F. , Hirakawa D. , Nojiri M. , Aizawa H. , Nishikiori H. , Soma R. , Tateyama M. , Watanabe K.
Published: October 2009

ABSTRACT: Integral bridges, comprising a continuous bridge girder (i.e. deck) integrated to a pair of abutments without using hinged and movable shoes (i.e. bearings), have been constructed to alleviate several inherent drawbacks of conventional bridges. It is shown that this conventional type of integral bridge still has the following problems: (1) large residual settlements in the backfill, developing a bump immediately behind the abutments, and the development of high residual earth pressure on the back of the abutments by seasonal thermal expansion and contraction of the girder, as well as by traffic loads on the backfill; and (2) large detrimental deformation of the backfill by seismic loads. To alleviate these problems, it is proposed to reinforce the backfill with geosynthetic reinforcement that is firmly connected to the full-height rigid facings (i.e. abutments). A newly proposed integral bridge, called the GRS integral bridge, is constructed in stages: first, geosynthetic-reinforced backfill; second, pile foundations (if necessary); third, full-height rigid (FHR) facings (i.e. abutments); and finally a continuous girder integrated to the top of the two abutments, without using shoes. A series of static cyclic loading tests, laterally on the facing and vertically on the crest of the backfill, and shaking-table tests were performed on models of the conventional and new types of integral bridge, as well as two conventional bridge types comprising RC gravity-type abutments and geosynthetic-reinforced soil-retaining walls, both supporting a girder via shoes. The test results showed high static and dynamic performance of the GRS integral bridge, despite its simple structure and construction procedure, and therefore its low construction cost.
Effects of temperature and stress on the short- and long-term compressive behavior of expanded polystyrene
Authors: Yeo S.-S. , Hsuan Y.G.
Published: October 2009

ABSTRACT: The short- and the long-term compressive behavior of an expanded polystyrene (EPS) geofoam were both evaluated to assess the effects of temperature and stress. The short-term compressive strength decreased bi-linearly as temperature increased with a transition point at the temperature of 43oC. For the long-term compressive creep behavior, three accelerated creep test methods were used in the evaluation: stepped isothermal method (SIM), time–temperature superposition (TTS), and time–temperature–stress superposition (TTSS). The results from these three tests were compared with that of the conventional creep test at room temperature. Due to the 43°C transition in the short-term compressive strength, the predicted creep strains from SIM and TTS, employing a higher temperatures than 43°C, were found to be much higher than those from the conventional test. Furthermore, the activation energies were significantly different at temperatures above and below 43°C. On the other hand, the creep strains predicted from the TTSS tests were similar to those from the conventional method. The TTSS tests employed test temperatures below 44°C. Instead of using elevated temperatures, higher stress levels were used to accelerate the creep. A modified four-parameter Weibull model was developed to predict the linear and non-linear creep behavior, and a good agreement was found with test data from TTSS and the conventional method.
Effect of polypropylene tape fibre reinforcement on swelling behaviour of an expansive soil
Authors: Viswanadham B.V.S. , Phanikumar B.R. , Mukherjee R.V.
Published: October 2009

ABSTRACT: The objective of this study was to examine the influence of discrete and randomly distributed fibres on heave of an expansive soil. One-dimensional swell tests were conducted on a remoulded expansive soil with and without fibres. In this study, fibre content was varied as 0.25 and 0.5% and fibre length as 30, 60 and 90 mm. A twin semi-circular-shaped fabricated mould with a front Perspex sheet was developed for testing. Digital imaging technique was used to observe heave of the soil in both unreinforced and fibre-reinforced conditions. Displacement profiles obtained from image analysis were used for interpreting swell or upward movement profiles of the specimens. Heave observed in the digital image analysis was compared with that obtained from dial gauge readings. Reduction in heave was directly proportional to fibre content and fibre length. Reduction in heave was the maximum at low aspect ratios at both fibre contents of 0.25 and 0.5%. Test results revealed that fibre length is a key factor that influences the reinforcing effect of fibre. Discrete and randomly distributed fibres were found efficacious in reducing heave.
The California Bearing Ratio Method for The Design of Flexible Roads and Runways
Authors: Davis E. H.
Published: October 2009

Introduction

One of the most important applications of soil mechanics to road and airfield engineering is to the calculation of the thickness and strength of pavement which has to be placed on a soil formation to provide a stable riding surface. Such calculation is known as pavement design.

For the purposes of pavement design, types of construction are divided into two classes: rigid pavements which are partly or entirely composed of concrete, and gexiile pavements which are composed of bituminous materials usually on a base of macadam or pitching. This paper is solely concerned with the design of flexible pavements.

In recent years a considerable number of methods of pavement design has been proposed for flexible pavements. Some of these methods are empirical and are based on experience of the performance of different roads or runways. Others are based on theoretical considerations of the stresses or strains involved and the remainder are based on a combination of the theoretical and empirical approaches. All the methods relate the thickness of construction to the strength of the soil on which the pavement is founded (the subgrade) and to the traffic conditions, the severity of which is usually given in terms of the maximum wheel load of the traffic using the pavement.

The many methods available can give widely different results. The theoretical aspects involved are not yet fully understood so that it is probably true to say that at present the empirical type of method generally gives more reliable results than the theoretical type. It should be realised that until comparatively recently the design of roads and runways often took little account of the type and condition of the soil foundation and that the use of any rational method of design represents an important advance in road and airfield engineering.

It was considered at the Road Research Laboratory that the. first aim should be to produce a reliable empirical method of pavement design for British conditions; the more theoretical approach has not, however, been neglected and a mathematical theory of thestresses in layered elastic systems has been developed by Fox (Ref. 1) and experimental work is in hand to check the values given by this theory.

Experience with a number of methods of pavement design has shown that an empirical method, known as the California bearing ratio (C.B.R.) method, was likely to prove the most suitable for use in this country, and this method was therefore selected for study. The present paper describes this method, and the investigations that have been made at the Road Research Laboratory to determine its reliability and the best procedure for its use.
The Soil of a Dirt Racetrack
Authors: Chapman L. J.
Published: October 2009

Synopsis

This short article describes the soil and sawdust mixture used as a cushion on a horse-racing track in Toronto, Canada. It consists of 12 per cent clay. 30 per cent silt, 55 per cent fine sand and 3 per cent coarse sand. A 3-inch layer of this soil mixed with a layer of hemlock sawdust 1 inch thick has given good service for 5 years. It was recénditioned after 4 years with another 1-inch dressing of sawdust.

L'article décrit briè le mélange de terre et de sciure employé sur le circuit d'un champ de courses à Toronto, Canada. Le mélange est composé de 12 pour cent d'argile, 30 pour cent de limon, 55 pour cent de sable fin et 3 pour cent de gros sable.

L'emploi d'une couche de trois pouces de profondeur de ce mèlange avec une couche de un pouce de sciure de sapin du Canada a donné de bons résultats pendant cinq ans. Après quatre ans, le circuit fut remis en ètat par l'addition d'une couche suppl`mentaire de un pouce de sciure.
Some Tests on Bored Piles in London Clay
Authors: Golder H. Q. , Leonard M. W.
Published: October 2009

Synopsis

The paper, describes, and gives the results of three loading tests carried out on bored piles constructed in the London clay at kensal Green Gas Works. Two of the tests were carried up to the ultimate load of the piles.

During the boring for the piles, samples of clay were taken for teats. and in two of the borings, loading tests were carried out on plates placed at the bottom of the boring at three different depths.

Further strength tests on clay from the same site are quoted, and a correlation is made between the shear strength and the loading tests. The results of the loading tests on piles do not agree with the value given by the Meyerhof-Murdock formula.

Further loading tests on bored piles in London clay at other sites are quoted in which the test load satisfactorily carried (not the ultimate load) is con- siderably higher than the ultimate given by Meyerhof and Murdock.

A method of design suggested by the Authors is stated.

Cette communication décrit et donne les résultats de trois essais de charge effectués sur des pieux forés, enfoncés dans l'argile de Londree a` usine à gaz de Kensal Green. Deux des essais ont été effectés jusqy'a` la charge limite des pieux. Pendant le forage, dee échantillons d'argile ont été prélevés, et en deux des sondages, des essais de charge out été effectués sur des plaquea se trouvaut au fond du sondage à trois profondeurs différentes. On cite d'autres essais de résistance sur l'argile provenant du même terrain, et on établit une corrélation entre la résistance au cisaillement et les essais de charge. Les résultats des essais de charge sur les pieux ne s'accordent pas avec la valeur donnée par la. formule Meyerhof-Murdock. On cite des essaie supplémentaires sur des pieux forésenfoncés dane l'argile de Londres en d'autres terrains, Où la charge d'essai portée d'une façon satisfaisante (non la charge limite) est beaucoup plus élevée. que la charge limite citée par Meyerhof et Murdock. Une méthode de construction proposée par les auteurs est donnée
Foundation of Structures on Over-Consolidated clay Layers in São Paulo
Authors: Vargas Milton
Published: October 2009

Synopsis

The problem of determining the settlement and bearing capacity of building and bridge foundations on partially-saturated, over-consolidated clay layers is approached in this Paper from an experimental point of view. The data for this study have been provided by the fast development of the city of São Paulo, Brazil, which is built on an extremely heterogeneous clayey formation. Emphasis is given to the relation between geological formations and foundation problems, each stratum having its peculiarities, a consideration of great importance in the solution of specific problems. As would be expected, the φ= 0 method for determination of the bearing capacity of foundation on these clays is not always quite valid. Although settlements of foundations on over-consolidated clay layers are not important they can be predicted with fair accuracy if certain assumptions are made.

Le problème qui consiste à déterminer l'effet detassement et la capacité de portage des fondations de bâtiments et de ponts sur des couches argileuses en partie saturées et surtassées est traité dans cet Article d'un point de vue expérimental. Les donées pour cette étude ont été fournies par le développement rapide de la ville de São Paulo, au Brésil, cette ville étant bâtie sur une formation argileuse très hétérogène. L'auteur y souligne en particulier le rapport entre les formations géologiques et les problèmes de fondations, chaque couche géologique ayant ses particularités dont l'étude est d'une grande importance pour la solution de problèmes déterminés. Comme on peut le prévoir, la méthode φ = 0, pour le calcul de la capacité de portage des fondations sur une telle argile, n'est pas toujours tout à fait valable. Bien que le tassement des fondations sur des couches d'argile surtassée ne soit pas de grande importance, on peut cependant en prédire l'ampleur avec quelque précision, si certaines suppositions sont faites.
A Rapid Method Of Determining in-situ CBR Values
Authors: Robinson P. J. M. , Lewis Tobias
Published: October 2009

Synopsis

The Paper relates how difficulties in using the CBR test led to the trial of two other types of soil bearing test in an effort to reduce the time taken to determine the bearing capacity in situ of an area of soil. Preliminary trials showed one of these, the 3-in. plate failure load test, to possess potentially satisfactory performance. Further experiments showed that the relationship: log10 (CBR) = 0·76837 log10 (plate load in lb.) – 1·64422 exists. When applying this in field work it should be remembered that the 3-in. plate measures the CBR value at a different depth below the surface from the CBR plunger.

Nous exposons ci-dessous comment des difficultés dans l'emploi de l'essai CBR nous a menés à l'épreuve de deux autres méthodes de déterminer la force portante du sol afin de réduire le temps nécessaire pour déterminer la force portante d'un périmètre de terrain in situ. Des essais préliminaires ont démontré que l'un d'entre ceux-ci, l'essai de charge de rupture sur un cercle de 3 pouces, a une fonction potentiellement satisfaisante. Les examens supplémentaires ont révéléque le rapport: log10 (CBR) = 0·76837 log10 (la charge sur le cercle en livres) – 1·64422 extste. Quant à l'application de ceci dans les travaux sur le terrain, il faut se rappeler que le cercle de 3 pouces mesure la valeur CBR à une profondeur différente à celle du plongeur CBR.
A Comparison of Values of liquid Limit Determined with Apparatus Having Bases of Different Hardness
Authors: Norman L. E. J.
Published: October 2009

Synopsis

A comparison has been made of the values of liquid limit of five clay soils determined with apparatus having bases of different hardnesses including one with a base of plastic material known as Micarta No. 221, stated to have the hardness required by the American standard test, and an apparatus with a base the hardness of which was as specified in the British specification, B.S. 1377: 1948. Tests were all made to determine the effect of any difference in the measured value of liquid limit on the “activity” of the clay soils and their shear strengths.

The American Micarta base was considerably harder than the hardness required by the British Standard, and the machine with the Micarta base gave values of liquid limit which were, in terms of moisture content, 3 to 4% less than those obtained with the machine with the base having the B.S. hardness. The effect of this difference on the “activity” of the clay soils was a 9 to 16% decrease in “activity” when the machine with the Micarta base was used.

The shear strengths of the five clay soils were 25 to 50% greater at the liquid limits measured with the machine with the Micarta base than at the liquid limit measured with the machine with the base having the B.S. hardness.

On a comparé les valeurs de limite de liquidité de cinq sols argileux, déterminées par appareils à bases de duretés différentes, dont une à base en matière plastique connue sous le nom de Micarta No. 221, certifiée comme ayant la dureté demandée l'épreuve américaine normale, et un appareil à base dont la dureté était celle spécifiée dans la spécification britannique, B.S. 1377: 1948. Les essais furent tous faits pour déterminer l'effet de toute différence dans la valeur mesurée de la limite de liquidité sur “l'activité” des sols argileus et leurs résistances au cisaillement.

La base américaine Micarte était considérablement plus dure que la dureté demandée selon la norme britannique et la machine à base Micarta donna des valeurs de limite de liquidité qui étaient en termes de teneur en eau, 3 à 4% inférieurs à ceux obtenus avec la machine à base de dureté B.S. L'effet de cette différence sur “l'activité” des sols argileux fut une diminution de 9 à 16% de “l'activité” lorsqu'on utilisa la machine à base Micarta.

Les résistances au cisaillement des cinq sols argileux étaient 25 à 50% plus grandes aux limites de liquidité mesurées avec la machine à base Micarta qu'à la limite de liquidité mesureé avec la machine a base de duretè spécification britannique.
Experiments on Model Piles with Enlarged Bases
Authors: Cooke R. W. , Whitaker Thomas
Published: October 2009

Synopsis

Although the behaviour of bored piles in London Clay is fairly well understood there is very little published data on the behaviour of the deep cylinder foundations with enlarged bases which are now being used to support some of the taller buildings in London. The model experiments described in the Paper were made to provide some information on the bearing capacity of this type of foundation and, in particular, to determine the proportions of the load carried by the shaft and the base. The models, which were of brass, had a shaft diameter of and both the length of the shaft and the diameter of the base were varied. A load cell was incorporated in the shaft to measure the base reaction. The tests were made by the constant rate of penetration method.

The tests showed that the resistance of the shaft was mobilized at very small penetration movements (about 0·5% of the shaft diameter) while penetrations of the order of 10·15% of the diameter of the base were necessary to develop the ultimate bearing capacity of the base given by Nc = 9. The results suggest that the minimum penetration movement at ultimate bearing capacity is obtained with the longest possible shaft and smallest diameter base.

Quoique le comportement des pilotis sondés dans l'argile londonienne soit assez notoire, très peu de détails ont été publiés au sujet des fondations à cylindres profonds avec bases dilatées, que l'on adopte actuellement pour soutenir un certain nombre des bâtiments plus élevés de Londres. Les essais sur maquette faisant l'objet de cette étude visaient à fournir des renseignements sur la portée de ce genre de fondations et, notamment, à déterminer la distribution de la charge sur le fût et sur la base. Les fûts des maquettes en bronze avaient ¾ pouce de diamètre et les longueurs furent variées comme les diamètres de la base. Les fûts incorporaient des cellules de charge pour mesurer les réactions de base. Les essais furent effectués par le systéme de vitesse de pénétration constante.

Les essais ont démontré que la résistance du fût se mobilise à la suite de mouvements de pénétration trés faibles (environ O·5% du diamètre du fût), tandis que des pénétrations de l'ordre du 10–15% se sont avérées nécessaires pour développer la portée limite de la base, donée par Nc = 9. Les résultats indiqueraient que le mouvement de pénétration minimum à la charge limite est atteint par le fût le plus long possible avec le diamètre de base le plus petit.
The Effect of Climatic Factors on Subgrade Moisture Conditions
Authors: Russam Kenneth , Coleman J. D.
Published: October 2009

Synopsis

The Paper describes recent research conducted at the Road Research Laboratory upon subgrade moisture conditions, with the aim of extending to a wider range of climates the research already carried out on moisture conditions beneath British pavements. Measurements made under several road and airfield pavements in both tropical and semi-tropical countries are considered. Where the water-table is close to the surface it is shown to be the main factor in determining the moisture condition of the subgrade irrespective of climate. Where the water-table is deeper, or non-existent, the relation between the subgrade moisture condition and the climatic water balance is examined, and evidence is presented for a relation between the suction of soil moisture in the subgrade and the Thornthwaite Moisture Index.

Cet article décrit des recherches récentes faites au Laboratoire de Recherches Routiéres (Road Research Laboratory) sur les conditions d'humidité des sous-sols, dans le but d'étendre à une plus grande variété de climats les recherches déjà faites sur les conditions d'humidité sous les revêtements britanniques. On y traite des mesures recueillies sous plusieurs revêtements de routes et de terrains d'aviation dans des pays tropicaux ainsi que dans des pays semi-tropicaux.

On montre qu'où la nappe aquifère est près de la surface elle est le facteur primordial permettant de définir les conditions d'humidité du sous-sol quelque soit la climat. Lorsque la nappe aquifère est plus profonde, ou non existante, on examine la relation entre les conditions d'humidité des sous-sols et l'équilibre d'eau climatique, et on offre les preuves d'une relation entre la suction de l'eau contenue dans le sous-sol et l'index de teneur en eau Thornthwaite
Thermal Conductivity of Saturated Leda Clay
Authors: Penner E.
Published: October 2009

Synopsis

The thermal conductivity of saturated remoulded Leda clay, a soil of post-glacial marine origin, increased from 5·5 to 7 B.t.u. in/sq.ft hour°F for an increase in dry density of 20 lb/cu.ft (75–95 lb/cu.ft) and decreased from 7 to 6 B.t.u. in/sq.ft hour°F for an increase of clay size particles from 39 to 60%.

The undisturbed soil appeared to have a higher thermal conductivity in the direction normal to the ground surface than in the remoulded condition, but insufficient results are available on which to base conclusions.

Extrapolating the thermal conductivity to 100% solids gave a value of 1l·8 B.t.u. in/sq.ft hour°F.The use of the value for the solid fraction in De Vries's method for predicting the conductivity gave reasonable agreement with measured results.

La conductibilité calorifique d'argile de Leda remoulée saturée, sol d'origine marine de perioda pré-glacière, a augmenté de 5,5 à 7 unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit pour un accroissement en densité sèche de 20 livres par pied cube (75–95 livres par pied cube) et a diminué de 7 à 6 unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit pour un accroissement de dimensions des particules d'argile de 39 à 60%.

Le sol intact a révélé une conductibilité thermique plus haute dans la direction perpendiculaire à la surface du sol dans une condition remaniée, mais les résultats obtenus sont insuffsants pour en tirer des conclusions.

En extrapolant la conductibilité thermique à 100% les solides ont donné une valeur de 11, s unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit. L'emploi de la valeur pour la fraction solide d'apres la méthode De Vries pour prédire la conductibilité s'accorde raisonnablement avec les résultats relevés.
Transient Development of the Free Surface in a Homogeneous Earth Dam
Authors: Brahma Suresh P. , Harr Milton E.
Published: October 2009

Synopsis

A general solution has been developed whereby the free surface can be predicted at any time in a homogeneous earth dam, founded on an impervious base, with any orientation of the upstream slope, given the history of the reservoir fluctuations.

Detailed solutions are obtained for reservoirs with constant head-water levels and with linear variations of head-water level for various inclinations of the upstream slope. Recognizing super- position to be valid, the effects of any history of head-water reservoir fluctuations may be studied (piecewise) as a series of linear steps. The results are reduced into graphical form and a systematic procedure is presented which renders the solutions easy to use.

Comparison between analytical results and experimental results obtained from a Hele-Shaw viscous flow model strongly indicates that the solutions presented may be used with some confidence with the exception of the portion of the free surface in the vicinity of the impervious base of the dam.

On a développé une solution générale selon laquelle on peut prédire à tout instant la surface libre sur un barrage de terre homogéne, construit sur une base imperméable avec n'importe quelle orientation sur la pente en amont, étant donné l'histoire des fluctuations du réservoir.

On a obtenu des solutions détaillées pour des réservoirs à niveau d'eau de charge constants et ayant des variations lineaires de niveau d'eau de charge pour diverses inclinaisons de la pente en amont. En admettant que la superposition soit valable, les effets des fluctuations passées de réservoir d'eau de charge peuvent être étudiées sous forme d'une série de marches linéaires. Les résultats sont condensés sous forme graphique et on expose une procédure systématique qui rend les solutions d'usage facile.

La comparaison entre les resultats analytiques et les resultats experimentaux obtenus avec un modèle à écoulement visqueux Hele-Shaw montrent nettement que les solutions présentées peuvent être utilisees avec une certaine confiance sauf pour la partie de la surface libre au voisinage de la base imperméable du barrage.
Foundations of the Tower of Pisa
Authors: Terracina Fernando
Published: October 2009

Synopsis

Having stated that consolidation is the main phenomenon in the Tower's underground, two causes are pointed out for the Tower's inclination: the difference in soil consistency on the sides of an east-west axial plane, and the inequality of the contact pressures as a consequence of the induced eccentricity of the load. In the Paper the historyof the second factor through the centuries is reconstructed. The increasing pressures on the southern side have increased the strength and reduced the compressibility, leading toan inversion of the primitive differences: therefore, to avoid danger, a partial redressing of the Tower would be better than the strengthening of the soil. Shifting of the inclination to 90/ (from the present 10%) will very likely be sufficient to bring all soil pressures below the equilibrium values corresponding to the present densities and to achievestabilisation. The straightening could be obtained by boring soil under the Tower on the northern side; and that would be possible according to various schemes, one of which is given below.

Après avoir établi que le phénombne principal qui s'est verifie dans le sol sousjacent la Tour est la consolidation, on distingue deux ordres de causes de I'inclinaison de la Tour: un originaire, 1'eterogénéite du sol des deux cotés d'un plan axial est-ouest, l‘autre dérivé l'excentricité de la résultante des pressions sur la base. L'histoire de ces pressions est reconstruite et on en tire la conséquence que l'eéterogénéité existante à l'époque de la construction est actuellement renversée, c'est à dire que maintenant au coté bas le sol, a une compressibilité beaucoup moindre et une résistance beaucoup plus grande que celles de l'autre coté. Par conséquence pour éliminer tout danger, plutôt qu'améliorer le sol, on devrait reduire les differences de pression en redressant partiellement la Tour; en portant l'inclinaison de lO%, (telle qu'elle est actuellement) a 9% par exemple, on conduirait très probablement toutes les pressions audessous des valeurs d'équilibre correspondantes aux densit´s actuelles et l'on obtiendrait ainsi lastabilisation dCfinitive de la Tour. Le redressement pourrait être obtenu par enléevement de matériau au coté haut; une des modalités possibles pour l'enlèvement est indiquée.
A New Consolidation Cell
Authors: Rowe Peter W. , Barden Laing
Published: October 2009

Synopsis

A consolidation cell is described in which the total stress is applied by means of hydraulic pressure acting across a convoluted rubber jack. This arrangement improves control of the drainage conditions, allowing the separation of the instant of loading from the commencement of drainage and permitting the measurement of initial pore pressures. Back pressures are readily applied.

A range of cell sizes meet the need to test larger samples of non-uniform deposits. The cell allows both vertical and radial flom tests for consolidation or direct permeability measurements.

On décrit une cellule de consolidation dans laquelle la contrainte totale est appliqudée au moyen de pression hydraulique agissant par un vérin à caoutchouc convoluté. Cet arrangement améliore le contrôle des conditions de drainage, permcttant la séparation de l'instant de charge du commenccmcnt du drainage ct par conséquent la mesure des pressions interstitielles initiales. Les centre-pressions sont appliquées rapidement.

Une gamme de dimensions de cellules satisfait au besoin d'essais de plus grands éhantillons de dépôts non-uniformcs. La cellule permet les essais d'écoulement verticaux ainsi que radiaux pour les mesures de consolidation ou de perméabilité directe.
Experimental Determination of the Shape Factors and the Bearing Capacity Factors of Sand
Authors: de Beer E. E.
Published: October 2009

Synopsis

In order to determine the values of the shape factors to be introduced in the formula of ultimate bearing capacity of shallow foundations, an extensive series of tests on small footings resting on fine sand was performed at Ghent. To obtain a homogeneous and given density the sand was placed in a fully automatic way, under control of the output and the height of fall of the sand. To eliminate the depth effect the overburden pressure was realized by air pressure in inflated rubber bags covering the surface of the sand.

From the tests formulae for the shape factors sq, sc and sγ are deduced. It appears that the shape factor sγ in the weight term is independent of the angle of friction, while the shape factors sq and sc are not.

In the formulae given for s and sc the influence of the state of strain is implicitly included; however, different formulae are given depending on whether the effect of the curvature of the intrinsic curve on the introduced shear strength parameters has been considered or not.

Afin de déterminer les coefficients de forme à introduire dans la formule de la capacité portante limite sous des fondations directes, un très grand nombre d'essais sur petites semelles reposant sur un sable fin ont été effectués à Gand. Afin d'obtenir une densite donnée, homogène, le sable a été placé d'une façon complètement automatique, permettant de régler la hauteur de chute et le débit. Afin d'éliminer l'influence du coefficient de profondeur, la surcharge latérale a été réalisée au moyen d'une pression d'air dans des sacs en caoutchouc recouvrant la surface du sable.

A partir des essais des formules ont été établies pour les coefficients de forme sq, sc et sγ. On constate que le coefficient de forme sγ dans le terme du poids-propre du sol est indépendant de l'angle de frottement interne, tandis que par centre les coefficients sq et sc varient avec cet angle.

Dans les formules données pour sq et sc l'influence de l'état de déformation est implicitement inclue. Toutefois les formules sont différentes, selon que le paramètre de cisaillement introduit tient compte ou non de la courbure de la couche intrinsèque du matériau.