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This paper presents a case history of a geotextile reinforced highway embankment constructed on a soft estuarine deposit installed with prefabricated vertical drains. The case history documents the geotechnical site characterization, embankment construction, and monitoring program. The loading response of the soft estuarine soil was monitored during construction using hydrostatic profile gauges, settlement plates, pneumatic piezometers, and slope inclinometers. Settlements of up to 1.3 m were measured under the 4 m high embankment. The deformation behaviour was interpreted qualitatively from the monitoring data using the general framework of elastic-plastic soil models. The effectiveness of the monitoring program is also briefly discussed. The paper provides performance details that make this case history useful to researchers studying the loading response of soft soils under a geotextile reinforced embankment. [ABSTRACT FROM AUTHOR]

This paper investigates the significant curling that occurs when thin soil layers undergo desiccation. Curling deformations, in the form of (1) lifting off from the edges (generating a concave surface), or (2) lifting off from the middle (creating a convex surface), are reported in the drying of soft soil and concrete pavements in the field. This paper presents experimental observations of significant curling of both forms 1 and 2 in wet soil specimens under controlled drying conditions. A theoretical explanation for curling is presented on the basis of unsaturated soil mechanics. The curling was primarily attributed to differential shrinkage strain increments that occur down the soil profile and their variation with the progression of desiccation. Making use of nonlinear elasticity theory under large deformations and measured properties, the shrinkage and curling deformations were modelled using the FLAC (Fast Lagrangian Analysis of Continua) computer program. The modelling approach appears to capture the observed behaviour of curling during desiccation. [ABSTRACT FROM AUTHOR]

This paper examines the constitutive behaviour of unsaturated mixtures of compacted sand-bentonite material. Two different techniques have been used to modify soil suction in laboratory specimens to examine the influence of suction on the behaviour of compacted materials. The two methods generated inherent differences in material fabric and therefore in stress-strain behaviour. The difference in microstructure generated by these two preparation techniques created different properties for the two series of specimens. This paper compares the behaviour of the two series of specimens and relates the observed mechanical behaviour to the initial soil fabric created by the two different preparation techniques. Specimens of similar compacted material were taken from two full-scale in-ground experiments conducted at Atomic Energy of Canada Limited's Underground Research Laboratory at Lac du Bonnet, Manitoba and sheared using the same triaxial equipment. The results are compared to the results of shearing laboratory compacted specimens. The research program demonstrates the need to understand the initial volume and suction states of plastic clays in order to predict the change in mechanical behaviour following a change in water content.Key words: constitutive relationships, unsaturation, laboratory tests, expansive soils, clays, shear strength.Cet article examine la loi de comportement de mélanges non saturés d'un matériau formé de sable-bentonite. Deux techniques différentes ont été utilisées pour modifier la succion du sol dans des spécimens en laboratoire afin d'examiner l'influence de la succion sur le comportement des matériaux compactés. Les deux méthodes ont généré des différences inhérentes dans la fabrique du matériau, et en conséquence, dans le comportement contrainte- déformation. La différence dans la microstructure générée par ces deux techniques de préparation ont créé de façon inhérente des propriétés différentes pour les deux séries de spécimens. Cet article compare le comportement des deux séries de spécimens et met en relation le comportement mécanique observé avec la fabrique initiale du sol créée par les deux différentes techniques de préparation. Des spécimens de matériaux compactés similaires ont été prélevés de deux expériences à grande échelle réalisées sur le terrain au laboratoire de recherche souterraine de l'AECL, et ont été cisaillés au moyen du même équipement triaxial. Les résultats sont comparés à ceux obtenus sur des spécimens compactés et cisaillés en laboratoire. Les résultats du programme de recherche démontrent le besoin de comprendre les états initiaux de volume et de contraintes dans les argiles plastiques pour prédire le changement dans le comportement mécanique à la suite d'un changement dans la teneur en eau.Mots clés : lois de comportement, non saturation, essais en laboratoire, sols gonflants, argiles, résistance au cisaillement.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The major rivers within the City of Winnipeg are founded in glacial Lake Agassiz clay and silt sediments that have low shear strength. As such, riverbank instabilities are a common issue along many stretches of the rivers. The use of rockfill columns has become an increasingly utilized approach for stabilizing failing banks. Recent cases in Winnipeg have shown that movements can occur following installation of rockfill columns. Uncertainty regarding the magnitude of these movements that is required to mobilize shearing resistance in the rockfill columns has resulted in situations where the stability of riverbanks following remediation has been questioned. This has provided a need to improve our understanding about how much movement a stabilized slope must undergo before sufficient shear resistance of the rockfill column will be mobilized. The results of experimental testing conducted to assess the shear mobilization of rockfill column materials using a large-scale direct shear test apparatus are presented in this paper. The testing methodology is described along with the test results. The results show that the development of material specifications, construction, and placement methods and appropriate methods of analysis requires understanding of the stress–strain properties of the in situ soil and the rockfill material. [ABSTRACT FROM AUTHOR]

A new hypoplastic model for clays with meta-stable structure is presented in this paper. A new method for incorporation of structure effects into hypoplastic models based on the modification of barotropy and pyknotropy factors is proposed and applied to an existing hypoplastic model for reconstituted clays. The new model is characterized by a simple calibration procedure and a small number of parameters. This makes the model particularly suitable for practical applications. The model is evaluated using experimental data for two natural soft clays. Thanks to the incrementally nonlinear character of the hypoplastic equation, the proposed model predicts behaviour of overconsolidated clays comparably to advanced kinematic hardening elastoplastic models. [ABSTRACT FROM AUTHOR]

Composite clay is a mixture of clay, as the main body, and aggregates, which are floating within the clayey matrix. The undrained behavior of composite clay in its natural or compacted state, e.g., core material of embankment dams, has great importance for geotechnical engineers. An extensive test program was conducted on kaolin–gravel and kaolin–sand mixtures to investigate various effects of aggregates on the mechanical behavior of the mixtures during strain-controlled monotonic and cyclic loadings. Monotonic test results reveal that increasing the aggregate content leads to a gradual increase in shear strength. Meanwhile, when the aggregate content is raised, the pore pressure increases for both monotonic and cyclic loading. It is also found that the presence of aggregates within a cohesive matrix leads to formation of a heterogeneous matrix in the clayey part of composite clays. This heterogeneity in turn causes pore pressure to be increased with an increase in the aggregate content during both monotonic and cyclic loading. In addition, test results show that aggregate size does not influence mechanical behavior appreciably. The results of this experimental research program are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper analyzes the effect of borehole disturbance, caused by installation of pressuremeter probes in clays, on the derived stress–strain curves. Both overpushing- and overcutting-induced disturbances are considered. It is shown that overpushing results in underestimation of the undrained shear resistance. In general, the degree of underestimation cannot be determined. As for overcutting, the derived stress–strain curves are characterized by high peak strengths. The degree of overestimation of the undrained shear strength may reach 100% for the case of a strain-hardening material. Determination of the strain that corresponds to the peak shear strength allows determination of the true stress–strain curve from the expansion test. Analysis of four well-documented case histories serves to illustrate the proposed approach. [ABSTRACT FROM AUTHOR]

It is well known that many landslides, which occur every year in the world, are triggered by rainfall. The mechanics of slope movements due to pore pressure changes are not completely understood, however, and thus are the focus of this paper. Both the case of first-time slides and that of landslide reactivation are examined. It is shown that simple models can reproduce the processes of slope failure and may help in predicting slope behaviour. [ABSTRACT FROM AUTHOR]

A 37-m thick layer of stratified clay encountered during a site investigation at Swann's Bridge, near the sea-coast at Limavady, Northern Ireland, is one of the deepest and thickest layers of this type of material recorded in Ireland. A study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline, the clay was deposited in a fresh-water glacial lake formed approximately 13,000 BP. The 37-m layer of clay can be divided into two separate zones. The lower zone was deposited as a series of laminated layers of sand, silt, and clay, whereas the upper zone was deposited as a largely homogeneous mixture. A comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit. The results obtained from these tests were complex and confusing, particularly the results of tests done on samples from the lower zone. The results of one-dimensional compression tests, unconsolidated undrained triaxial tests, and consolidated undrained triaxial compression tests showed that despite careful sampling, all of the specimens from the lower zone exhibited behaviour similar to that of reconstituted clays. It was immediately clear that the results needed explanation. This paper studies possible causes of the results from tests carried out on the lower Limavady clay. It suggests a possible mechanism based on anisotropic elasticity, yielding, and destructuring that provides an understanding of the observed behaviour. [ABSTRACT FROM AUTHOR]

This paper describes the instability in the foundation of the Caudalosa tailings dam in Peru. The instability threatened collapse of the structure along with the risk of unacceptable contamination of the River Escalera, located immediately downstream of the toe of the dam. At the time of these investigations, large deformations were in progress. The head scarp of the potential slide, located in the stored tailings, had reached a height of 2 m. Visual observations, as well as subsurface investigations, indicated that the instability was due to the presence of soft to medium plastic clay in the foundation. Emergency stabilization was successfully achieved by the construction of large trenches at the downstream toe, allowing the low consistency clay to be removed and backfilled with compacted mine waste rock. Other secondary stabilizing measures that were undertaken are also described.Key words: clay, dam, instability, remediation, stabilization, slide, tailings.L'article décrit l'instabilité de la fondation de la digue de résidus de Caudalosa au Pérou. L'instabilité menaçait de causer la rupture de la structure avec le risque d'une contamination inacceptable de la rivière Escalera localisée immédiatement en aval du pied de la digue. Au moment de ces investigations, de grandes déformations étaient en train de se produire. L'escarpement principal du glissement, localisé dans les stériles entreposés avait atteint une hauteur de 2 m. Des observations visuelles, de même que des investigations du sous-sol ont indiqué que l'instabilité était due à la présence d'argiles molles à moyennement plastiques dans la fondation. Une stabilisation d'urgence a été réalisée avec succès en excavant de grandes tranchées au pied aval pour enlever l'argile de faible consistance et la remplacer par un remblayage de résidus de roc compactés. On décrit également d'autres mesures secondaires de confortement qui ont été appliquées.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Nakdong River plain is one of the few areas in Korea where soft clays have been deposited. Although many site investigations related to large-scale reclamation works have been carried out over the past 10 years, soil profiles still need to be better characterized. The Pusan clays at this location constitute an interesting topic for researchers both in and outside Korea due to their geological complexity, unusually great thickness, very low overconsolidation (OCR) values, large consolidation settlement, and the effects of artesian pressure. This paper represents the first comprehensive review of Pusan clays and collates extensive existing and new geotechnical data. These data are then analyzed within the frameworks of both classical and new developments in soft clay engineering to address the problems mentioned above.Key words: Pusan, soft clay, intrinsic compression, geotechnical properties.La plaine de la rivière Nakdong est une des quelques régions en Corée où des argiles molles ont été déposées. Quoique plusieurs études aient été réalisées sur le terrain au cours des dix dernières années en relation avec des travaux de réhabilitation à grande échelle, les profils de sols requièrent une meilleure caractérisation. Les argiles de Pusan sur ce site constituent un sujet intéressant pour les chercheurs tant à l'intérieur qu'à l'extérieur de la Corée à cause de leur complexité géologique, de leur épaisseur exceptionnellement grande, de leur très faible valeur de surconsolidation (OCR), du grand tassement en consolidation, et des effets de pression artésienne. L'article présente la première revue d'ensemble des argiles de Pusan, et collige de nombreuses données géotechniques existantes et nouvelles. Ces données sont alors analysées dans le cadre des développements tant classiques que nouveaux de la construction sur les argiles molles pour traiter les problèmes mentionnés ci-haut.Mots clés : Pusan, argile molle, compression intrinsèque, propriétés géotechniques.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A parcel of land just south of Ottawa at Gloucester has been the site of an unusual amount of geotechnical research over the past 45 years. The parcel was recently to have been placed on the open real estate market but has been saved for scientific purposes and is now designated as "Canadian Geotechnical Research Site No. 1 at Gloucester". This paper presents an outline of the research that has been conducted at the site, in four general divisions, namely compressibility, strength, deformation, and soil property improvement. It is hoped that the site will stimulate the development and evaluation of new tools and techniques, foster scientific cooperation and information exchange, and allow the results of research involving the site to improve the state of practice, education, and research.Key words: sensitive clay, compressibility research, strength research, deformation research, soil improvement research.Un montant exceptionnel de recherche en géotechnique a été faite durant les 45 dernières années sur un morceau de terrain juste au sud d'Ottawa à Gloucester. Ce terrain devait jusqu'à récemment être vendu mais il a été sauvegardé à des fins scientifiques et est maintenant connu sous le nom « Site No. 1 de recherche canadienne en géotechnique à Gloucester ». Cet article présente les grandes lignes de la recherche effectuée, en quatre divisions générales, soit la compressibilité, la résistance, la déformation et l'amélioration des propriétés des sols. Il y a bon espoir que ce site va stimuler le développement et l'évaluation de nouveaux outils et techniques, entretenir une coopération scientifique et un échange d'information, et permettre à améliorer l'état de la pratique, l'éducation ainsi que la recherche avec les résultats obtenus à même les essais effectués sur le site.Mots clés : argile sensible, recherche sur la compressibilité, recherche sur la résistance, recherche sur la déformation, recherche sur l'amélioration des propriétés des sols. [ABSTRACT FROM AUTHOR]