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Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High stress consolidation tests (up to 30 MPa) were carried out on slurries made up of three bentonites considered as possible constituents for engineered clay barriers used for nuclear waste disposal at great depth (Na Kunigel, Na-Ca MX80 Wyoming clay, and Ca Fourges clay). Water retention curves (WRCs) were determined for a wide range of suctions (up to 305 MPa). A bilinear shape for the compression curves and the WRCs was observed in the three clays, with significant changes occurring in the 0.4–1 MPa suction–stress range. The permeability and the coefficient of consolidation were also determined during the compression tests. In the WRCs and compression curves, the two clays containing Na[sup +] exhibited a similar behaviour, which was different from that of the Ca[sup 2+] clay. The coefficient of consolidation for the three clays was decreasing in the 0.4–1 MPa stress range and increasing at higher stresses. Data were interpreted in the light of existing experimental observations on the microstructural changes of similar swelling clays carried out by various authors, which obtained compatible and coherent results. The diffuse double theory, often used in the interpretation of the volume change behaviour of swelling clays, was also considered. Under higher stresses (> 2 MPa), the compressive behaviour appeared to be linked to the expulsion water molecules that form the hydration shells around exchangeable cations inside the domains formed of staked clay plates. The permeability properties of the Ca[sup 2+] and Na[sup +] clays were linked to the microstructure features and to the WRCs, whereas the changes in the coefficients of consolidation during compression were linked to the changes in soil stiffness.Key words: consolidation, swelling clay, permeability, exchangeable cations, diffuse double layer, adsorbed water.Des essais de consolidation sous des contraintes élevées (jusqu'à 30 MPa) ont été réalisés sur des boues constituées de trois bentonites considérées comme des constituants possibles de barrières ouvragées pour l'entreposage de déchets nucléaires à grande profondeur (Na Kunigel, Na-Ca MX80 Wyoming clay et Ca Fourges clay). Les courbes de rétention d'eau ont également été déterminées sur une large plage de succion (jusqu'à 305 MPa). On a observé une forme bilinéaire des courbes de compression et de rétention d'eau pour les trois argiles, avec des changements significatifs se produisant dans la plage de 0.4–1 MPa de succion–contrainte. Les déterminations de la perméabilité et du coefficient de consolidation ont aussi été réalisées au cours des essais de compression. Dans les courbes de compression et de rétention d'eau, les deux argiles contenant du Na+ présentent un comportement similaire, différent de celui de l'argile Ca[sup 2+] . Le coefficient de consolidation des trois argiles diminue dans la plage de contraintes de 0.4–1 MPa et augmente à des contraintes plus élevées. Les données ont été interprétées à la lumière des observations expérimentales existantes sur les changements de microstructure d'argiles gonflantes similaires faites par divers auteurs qui ont obtenu des résultats compatibles et cohérents. On a aussi considéré la théorie de double couche diffuse, souvent utilisée dans l'interprétation du comportement volumique des argiles gonflantes. À des contraintes plus élevées (>2 MPa), le comportement en compression semble être relié à l'expulsion des molécules d'eau qui forment les coquilles d'hydratation autour des cations échangeables, dans les domaines formés par les feuillets argileux empilés. Les propriétés de perméabilité des argiles Ca[sup 2+] et Na+ sont reliées à des caractéristiques de microstructure et aux courbes de rétention d'eau, alors que les changements de cv durant la compression sont reliés aux changements de rigidité du sol.Mots clés : consolidation, argile gonflante, perméabilité, cations échangeables, double couche diffuse, eau adsorbée.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The results of laboratory and in situ permeability tests can be used to predict the total leakage rate of a soil–bentonite or clay liner. This prediction, however, ignores the large influence that minor defects may have on the total leakage. In Quebec, hundreds of municipal wastewater ponds have been filled with water to measure their total leakage rate before approval. The design criteria and the equations to be used for the full-scale performance test are briefly reviewed with their capacities to detect hydraulic deficiencies. Several case histories are presented to illustrate various problems: excessive leakage of a stable soil–bentonite mix, washing of bentonite in a soil–bentonite mix, internal erosion of a natural clay liner through an inadequate sand filter, and effects of freezing on the total leakage of a clay liner.Key words: liner, clay, bentonite, permeability, performance, full-scale testLes résultats d'essais de perméabilité en laboratoire et in situ peuvent servir à prédire le débit de fuite total d'un tapis d'étanchéité en sol–bentonite ou en argile. Cette prédiction, cependant, ignore l'influence que des défauts mineurs peuvent avoir sur la fuite totale. Au Québec, des centaines de bassins d'eau usée municipale ont été remplis d'eau pour mesurer leur fuite totale avant approbation. Les critères de conception et les équations à utiliser pour cet essai de performance à pleine échelle sont examinées brièvement avec leurs capacités de détecter les défauts hydrauliques. Plusieurs études de cas sont présentés pour illustrer divers problèmes: fuite excessive d'un sol–bentonite stable, délavage de la bentonite d'un mélange sol–bentonite, érosion interne d'une argile naturelle à travers un sable filtrant inadéquat, et effets du gel sur la fuite totale d'un tapis en argile.Mots clés : tapis, argile, bentonite, perméabilité, performance, essai en pleine grandeur. [ABSTRACT FROM AUTHOR]

To understand the deformation of ultrasoft soil in a viscous state, compression tests were carried out using a small-scale consolidometer equipped with pore-pressure transducers at three locations. Deformation behavior was monitored with both settlement and pore-pressure measurements. The transitional points from slurry to soil were determined from the settlement rate, change in void ratio, change in permeability, and pore-pressure dissipation. It was found that the transitional void ratio determined from the settlement rate is smaller than that determined from the commencement of pore-pressure dissipation. The transitional void ratio varied slightly for samples with different initial moisture contents determined based on pore-pressure considerations. The variation was due to the difference in sample thickness which affected the initiation of pore-pressure dissipation at the bottom of sample. In reality, the void ratio at transition could be larger than those determined from both settlement and pore pressure.Key words: ultrasoft soil, deformation, compression, pore pressure, permeability.Pour comprendre la déformation du sol ultra-mou dans un état visqueux, des essais de compression ont été réalisés dans un consolidomètre à petite échelle équipé d'un capteur de pression interstitielle à trois niveaux. Le comportement en déformation a été observé par des mesures de tassement et de pression interstitielle. Les points de transition d'une boue à un sol ont été déterminés à partir du la vitesse du tassement, du changement dans le rapport de vide, du changement de perméabilité, et de la dissipation de la pression interstitielle. On a trouvé que le rapport de vide transitionnel déterminé par la vitesse de tassement est plus petit que celui déterminé à partir du début de la dissipation de la pression interstitielle. Le rapport de vide transitionnel déterminé en partant de considérations sur la pression interstitielle varie légèrement pour des échantillons ayant différentes teneurs en eau initiales. La variation était due à la différence dans l'épaisseur de l'échantillon qui était affecté par l'initiation de la dissipation de la pression interstitielle à la base de l'échantillon. En fait, le rapport de vide à la transition pourrait être plus grand que ceux déterminés en partant tant du tassement que de la pression interstitielle.Mots clés : sol ultra-mou, déformation, compression, pression interstitielle, perméabilité.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The present research concerns a comparative analysis of the possible methods for estimating soft silty clay permeability to be used in the analysis of consolidation. For this purpose the consolidation response of a thick and homogeneous, instrumented soft silty clay deposit, on which an embankment was constructed, is back-analyzed using the finite-element method. To model the consolidation process, permeability data are carefully determined both from laboratory and in situ piezocone tests. One-dimensional and triaxial permeability test data are compared with the results of piezocone dissipation tests, the latter interpreted using four different solutions. The effects of anisotropy on permeability characteristics influencing the consolidation rate are also discussed.Key words: consolidation, embankment, finite-element analyses, permeability, piezocone, soft silty clay.La présente recherche traite d'une analyse comparative des méthodes possibles pour évaluer la perméabilité devant être utilisée dans l'analyse de la consolidation de l'argile limoneuse molle. À cette fin, on analyse à rebours au moyen de la méthode d'éléments finis la réponse en consolidation d'un dépôt instrumenté épais et homogène d'argile limoneuse molle sur lequel un remblai a été construit. Afin de modéliser le processus de consolidation, les données de perméabilité sont déterminées minutieusement au moyen d'essais en laboratoire et d'essais de piézocône in situ. Les données d'essais de perméabilité unidimensionnels et triaxiaux sont comparées avec les résultats des essais de dissipation au piézocône qui ont été interprétés au moyen de différentes solutions. On discute également les effets de l'anisotropie sur les caractéristiques de perméabilité influençant la vitesse de consolidation.Mots clés : consolidation, remblai, analyse en éléments finis, perméabilité, piézocône, argile limoneuse molle. [Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A pilot test was carried out at a land reclamation project site to study the effect of vertical drains on the rate of consolidation of a marine clay deposit in Singapore. Theoretical and numerical analyses were conducted to interpret the field measurements of pore pressure and settlement, and consolidation parameters were back-calculated. The back-calculated preconsolidation pressure is similar to that obtained from the laboratory consolidation test on undisturbed samples, but the field-deduced compression index is generally larger than that measured in the laboratory. The coefficient of consolidation back-calculated from the settlement measurement is larger than that from the pore-pressure measurement. The coefficient of consolidation for horizontal flow obtained from the Rowe cell test, which is comparable to that back-calculated from the field settlement measurement, is recommended for the preliminary design of vertical drains without the need of considering the smear effect.Key words: clays, consolidation, ground improvement, numerical modelling and analysis, permeability, vertical drains.Un essai pilote a été réalisé sur le site d'un projet de réhabilitation de terrain pour étudier l'effet des drains verticaux sur la vitesse de consolidation d'un dépôt d'argile marine à Singapore. Des analyses théorique et numérique ont été réalisées pour interpréter les mesures sur le terrain de la pression interstitielle et du tassement, et des paramètres de consolidation ont été calculés à rebours. La pression de consolidation calculée à rebours est similaire à celle obtenue par l'essai de consolidation en laboratoire sur des échantillons non remaniés, mais l'indice de compression déduit du terrain est généralement plus grand que celui mesuré en laboratoire. Le coefficient de consolidation calculé à rebours à partir des mesures de tassement est plus grand que celui obtenu par la mesure de la pression interstitielle. Le coefficient de consolidation pour l'écoulement horizontal obtenu par l'essai avec la cellule de Rowe, qui est comparable à celui calculé à rebours à partir de la mesure du tassement sur le terrain, est recommandé pour la conception préliminaire des drains verticaux sans prendre en compte l'effet de souillure d'argile remaniée.Mots clés : argiles, consolidation, amélioration des terrains, modélisation et analyse numériques, perméabilité, drains verticaux.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Due to the effect of structure, Bangkok clay is stable in a metastable state. Its void ratio, e, is the summation of the void ratio sustained by the intrinsic fabric, eR, and the additional void ratio due to the structure, es. The intrinsic state line (eR versus log σ′v, where σ′v is the effective vertical stress) is developed in terms of the void ratio at the liquid limit, eL. At the post-yield state, es is inversely proportional to σ′v. The residual additional void ratio, esr, which cannot be eliminated by the increase in effective vertical stress, is constant at about 0.20 for soft Bangkok clay and 0.12 for medium stiff Bangkok clay. From these findings and the ideal condition of zero compression at the pre-yield state, the field yield stress and field compression curve can be assessed. The undrained shear strength is directly related to the field yield stress, since both reflect the structure. The soil structure does not significantly influence the permeability. The permeability of the clay in structured and destructured states is identical under the same void ratio and can be determined from the generalized state parameter, e/eL. These observations result in a simple and practical method for assessment of the engineering properties of natural Bangkok clay. [ABSTRACT FROM AUTHOR]