Search

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.)

A comprehensive campaign of laboratory and field tests has been conducted to characterize the behaviour of tailings from a hard-rock mine. Cyclic triaxial, direct simple shear, and triaxial simple shear tests have shown that the contractive tailings are susceptible to liquefaction and that their behaviour is similar to loose sand despite their higher fines' content. To model the behaviour of tailings' impoundments in dynamic simulations, the PM4Sand constitutive model is calibrated based on the dataset presented here. Some of the model parameters are defined based on consolidation and compression tests, while the critical state line (CSL) is defined based on the results of monotonic triaxial and direct simple shear tests. The CSL is lower for tailings than for most natural sands, which is consistent with previous studies. The calibrated model can reproduce reasonably well the monotonic behaviour and provides an excellent fit of the cyclic strength curves measured in the lab at different confining pressures and density index. The results presented in this paper indicate that the PM4Sand model can be used to simulate the cyclic behaviour of low-plasticity, hard-rock tailings. The proposed procedure also provides general guidelines regarding model calibration for other types of tailings. [ABSTRACT FROM AUTHOR]

The paper deals with three issues relevant to the application of TDR methods for monitoring water content in compacted clay soils: (i) the dependence on dry density, (ii) the ability to monitor changes in water content in clay soil approaching saturation, and (iii) difficulties in performing efficient and reliable calibrations. A calibration scheme which inherently controls dry density of the specimen has been developed and applied. The methodology creates continuous calibration curves over a range of volumetric water content from a single test specimen. The new approach has been applied in monitoring the advance of a wetting front through a compacted swelling clay in a laboratory environment. [ABSTRACT FROM AUTHOR]

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.)

Many offshore geotechnical problems—such as cyclic T-bar penetration and lateral buckling of pipelines—are affected by the tendency of fine-grained soils to strain-soften due to remoulding. Careful calibration of the constitutive model parameters that control strain softening is essential for accurate simulation of these processes. This is usually achieved by matching constitutive model response with standard element test data, which implicitly assumes that homogeneous stress/strain fields exist within the sample. However, popular element test protocols (e.g., triaxial, simple shear) cannot apply sufficient deformation—at least as measured at the boundaries—to achieve fully remoulded conditions. This work explores the potential to determine strain-softening parameters experimentally, directly from image-based full-field deformation measurements and external loading data. Artificial data generated from finite element simulations of biaxial compression and T-bar penetration tests, using a non-locally regularised strain-softening constitutive model based on Modified Cam Clay, are then used to demonstrate the potential of the proposed technique. The results demonstrate significant potential for the application of the technique to identify constitutive parameters from full-field measurements even when polluted with modest measurement noise. [ABSTRACT FROM AUTHOR]

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.)

Simple numerical methods that allow to obtain stress and strain paths in sand during self-boring pressuremeter tests are presented in this paper. The material is considered to undergo deformation in drained and plane-strain conditions. The flow rules of Rowe, Cambridge-type (Cam clay and Nova) model, and the sawtooth model are used in the analysis. Elastic strains are also considered in relation with the flow rule of Rowe. The proposed approach has been evaluated using a reference pressuremeter test performed on Ticino sand in a calibration chamber. The results indicate that the stress–strain–volume change responses of the sand predicted by the various models are quite similar, with and without consideration of the elastic strain components. Des méthodes numériques simples, qui permettent d’obtenir les cheminements de contraintes et déformations pendant les essais pressiométriques autoforeurs dans le sable, sont présentées dans cet article. Le matériau est considéré être sollicité en conditions drainées et en déformation plane. Les règles d’écoulement plastique utilisées sont celles de Rowe, de type Cambridge (Cam clay et Nova), et le modèle « dents de scie ». L’approche proposée tient aussi compte des déformations élastiques dans le cadre du modèle de Rowe. La méthode a été évaluée à l’aide d’un essai pressiométrique de référence, effectué dans une chambre de calibration, sur le sable de Tessin. Les résultats indiquent que les réponses du sable en termes des relations contraintes – déformations – changements de volume, prédites par les différents modèles, sont assez similaires, avec ou sans la prise en compte des déformations élastiques. [ABSTRACT FROM AUTHOR]

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.)

A new simple system for accurately measuring overall total volume changes in unsaturated soil specimens with a triaxial apparatus is introduced in this paper. The basic principle of the measuring system is to record changes in the differential pressure due to changes in the water level inside an open-ended, bottle-shaped inner cell caused by volume change in the specimen and inside a reference tube using an accurate differential pressure transducer. Several important steps were taken to improve the accuracy and sensitivity of the measuring system. Detailed calibrations were carried out to account for apparent volume changes as a result of changes in cell pressure, fluctuation in the ambient temperatures, creep in the inner cell wall, and relative movement between the loading ram and the inner cell. The calibration results demonstrate that the measuring system is reasonably linear, reversible, and repeatable. The estimated accuracy of the measuring system is in the order of 32 mm[sup 3] (or 0.04% volumetric strain for a triaxial specimen 38 mm in diameter and 76 mm in height) once the system is properly calibrated.Key words: unsaturated soils, volume-change measurement, open-ended, bottle-shaped, inner cell, differential pressure, calibration.On introduit dans cet article un nouveau système simple pour mesurer précisément les changements de volume totaux globaux dans les spécimens de sol non saturé avec un appareil triaxial. Le principe de base du système de mesure consiste à enregistrer les changements dans la pression différentielle dus aux changements des niveaux d'eau dans une cellule intérieure à bout ouvert et en forme de bouteille causés par le changement de volume du spécimen et à l'intérieur d'un tube de référence utilisant un capteur de pression différentielle (DPT). Plusieurs étapes importantes ont été suivies pour améliorer la précision et la sensibilité du système de mesure. Des calibrages détaillés ont été réalisés pour tenir compte des changements de volume apparents dus aux changements de la pression cellulaire, à la fluctuation des températures ambiantes, au fluage dans la paroi de la cellule intérieure et au mouvement relatif entre le piston de chargement et la cellule intérieure. Les résultats du calibrage démontrent que le système de mesure est raisonnablement linéaire, réversible et répétitif. La précision estimée du système de mesure est de l'ordre de 32 mm[sup 3] (ou 0,04 % de la déformation volumétrique pour un spécimen triaxial de 38 mm de diamètre et de 76 mm de hauteur) lorsque le système est convenablement calibré.Mots clés : sols non saturés, mesure de changement de volume, bout ouvert, forme de bouteille, cellule intérieure, pression différentielle, calibrage.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The reclamation for the new airport at Chek Lap Kok in Hong Kong included the placement of a substantial volume of sand fill by various hydraulic placement techniques, which resulted in a wide range of as-placed densities of the sand fill. This paper described the use of cone penetration tests (CPT) on the evaluation of the possible ranges of density achievable by various hydraulic placement methods adopted in the construction of the new airport. The results of the CPT indicated that the placement technique is one of the most important factors in controlling the as-placed density of hydraulically placed sand fill. There is a marked contrast in cone tip resistance (and the associated relative density) profiles for the sand fills formed by subaerial and subaqueous placement methods, in which the cone tip resistance of the sand fill formed by subaerial placement is substantially higher than that of the sand fill formed by subaequeous placement. The results confirm that dense sand fill cannot be formed by subaqueous placement methods. The weakest zone is generally located just beneath the water level where fill is placed by subaqueous discharge.Key words: sand, hydraulic fill, cone penetration test, calibration chamber test, in situ density.Le remblayage pour le nouvel aéroport à Chek Lap Kok de Hong Kong comprend la mise en place d'un volume substantiel de remblai de sable par différentes techniques de mise en place hydraulique, qui ont résulté en une large plage de densités en place du remblai de sable. Cet article décrit l'utilisation de l'essai de pénétration au cône (CPT) pour l'évaluation des plages possibles de densité qui peuvent être obtenues par différentes méthodes de mises an place hydrauliques adoptées pour la construction du nouvel aéroport. Les résultat de CPT indiquent que la technique de mise en place est un des facteurs les plus importants pour le contrôle de la densité en place de sable remblayé par méthode hydraulique. Il y a un contraste marqué entre les profils de résistance à la pointe (et la densité relative correspondante) pour les remblais de sable mis en place par des méthodes subaériennes ou sous l'eau, le premier étant appréciablement plus élevé. Les résultats confirment qu'un remblai de sable dense ne peut pas être obtenu par des méthode de mise en place sous l'eau. La zone la plus faible est en général localisée juste sous le niveau d'eau, là où la déposition du matériau de remblayage se fait par décharge sous-l'eau.Mots clés : sable, remblai hydraulique, essai de pénétration au cône, essai en chambre de calibrage, densité in situ.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

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.)

A calibration chamber has been developed to conduct laboratory-controlled cone penetration tests in unsaturated soils. The chamber allows independent application of lateral and vertical pressures to an unsaturated soil specimen. Horizontal pressure is applied by cell water pressure pushing on a rubber membrane enclosing the specimen, while vertical pressure is maintained by a hydraulic loading ram at the base of the specimen. Suction is controlled using the axis-translation technique. Air pressure is applied to the top of the chamber where it spreads uniformly across the top of the specimen. Pore-water pressure is applied through eight high air-entry value porous disks embedded in the bottom plate. A particularly original aspect of the chamber design is the specimen formation system comprising four moveable cylinder quarters, which enables the creation of specimens of repeatable properties from a variety of soil types. The results of typical cone penetration tests conducted on dry, saturated, and unsaturated sand specimens are presented and highlight the contribution of suction to cone penetration resistance. Une chambre de calibrage a été développée pour effectuer des essais de pénétration au cône contrôlés en laboratoire pour des sols non saturés. La chambre permet d'appliquer des pressions latérales et verticales de façon indépendantes sur un échantillon de sol non saturé. La pression horizontale est appliquée par la pression de l'eau sur la cellule qui pousse sur une membrane en caoutchouc qui entoure l'échantillon, tandis que la pression verticale est maintenue par un bélier de chargement hydraulique à la base de l'échantillon. La succion est contrôlée à l'aide de la technique de translation de l'axe. La pression d'air est appliquée à la partie supérieure de la chambre et est distribuée uniformément sur le dessus de l'échantillon. La pression interstitielle est appliquée par huit disques poreux ayant une pression à l'entrée d'air élevée placés dans la plaque du bas de la chambre. Un aspect original du design de la chambre est le système de formation des échantillons, qui comprend quatre quarts de cylindre mobiles, ce qui assure la création d'échantillons avec des propriétés reproductibles pour une variété de types de sols. Les résultats d'essais de pénétration au cône typiques réalisés sur des échantillons de sable sec, saturé et non saturé sont présentés et mettent en évidence la contribution de la succion à la résistance à la pénétration du cône. [ABSTRACT FROM AUTHOR]

As part of a study to develop load and resistance factor design (LRFD) codes for foundation structures in South Korea, resistance factors for the static bearing capacity of driven steel pipe piles were calibrated in the framework of the reliability theory. A database of 52 static load test results was compiled, and the data from these load test piles were sorted into two cases: a standard penetration test (SPT) N-value at pile tip (i) less than 50 and (ii) equal to or more than 50. Reliability analyses and resistance factor calibration for the two static bearing capacity analysis methods adopted in the Korean Design standards for foundation structures were performed using the first-order reliability method (FORM) and the Monte Carlo simulation (MCS). Reliability indices and resistance factors computed by the MCS are statistically identical to those computed by FORM. Target reliability indices were selected as 2.0 and 2.33 for the group pile case and 2.5 for the single pile case. The resistance factors recommended from this study are specific for the pile foundation design and construction practice and the subsurface conditions in South Korea. Des facteurs de résistance pour la capacité portante de pieux faits de tuyaux d’acier ont été calibrés dans le cadre de la théorie de fiabilité, ceci en tant que partie d’une étude sur le développement de codes de facteurs de chargement et de résistance pour des fondations de structures en Corée du Sud. Une base de donnée de 52 essais de chargement statique a été compilée, et les données de ces pieux d’essais ont été classés en deux catégories : essai de pénétration standard (SPT) N à la pointe du pieu (i) de moins de 50 et (ii) égal ou supérieur à 50. Les analyses de fiabilité et le calibrage des facteurs de résistance pour les deux méthodes d’analyse de la capacité portante adoptées par les normes Design standards for foundation structures de la Corée ont été effectuées à l’aide de la méthode de fiabilité de premier ordre (FORM) et la simulation Monte Carlo (MCS). Les indices de fiabilité et les facteurs de résistance obtenus avec la MCS sont statistiquement identiques à ceux obtenus par FORM. Les indices de fiabilité visés ont été choisis comme 2,0 et 2,33 pour le cas de groupement de pieux, et de 2,5 pour le cas de pieux uniques. Les facteurs de résistance recommandés suite à cette étude sont spécifiques à la conception et à la construction de pieux dans les conditions de la Corée du Sud. [ABSTRACT FROM AUTHOR]

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.)

Thermal conductivity (TC) sensors, which provide estimates of matric suction, were used in a field experiment designed to characterize unsaturated water movement through coarse mine waste rock at a mine site in northern Saskatchewan. Two years oF monitoring data were used to evaluate long-term TC sensor performance and accuracy. Thermal conductivity sensor output requires corrections of sensor hysteresis and changes in ambient temperature. A correction method for ambient temperature is derived. A comparison oF the uncorrected field measurements with the values corrected for both hysteresis and ambient temperature indicates that the magnitude of these corrections can be similar. Corrected TC sensor measurements are compared to measurements of matric suction made using tensiometers. Thermal conductivity sensor response to the initial arrival of a wetting front lagged 1 3 days behind the tensiometer measurements. The TC sensor data tended to overestimate matric suction in the waste rock, when compared to the tensiometer data. Long-term drift in the TC sensors located at depths oF 50 cm and below (where the sensors have been continuously exposed to matric suctions less than 20 kPa) has lead to data that are not interpretable using the calibration curves derived prior to sensor emplacement in the waste rock pile. [ABSTRACT FROM AUTHOR]