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The behavior of interfaces between granular materials in zoned embankment dams can influence their overall behavior. Soil--structure interfaces have been largely studied, but only a few analyses of interfaces between the granular materials composing rockfill dams have been realized. Consequently, there is a need to consider the influence of material interfaces within dams. Numerical modeling of a rockfill dam was performed to simulate its mechanical behavior during the construction phase. The behavior was analyzed based on the numerical methods used to model the interfaces and on interface characteristics through sensitivity analyses. Particular attention was paid to the influence of interface shear strength on the dam shear deformations, settlements, and plasticity. The numerical results highlight that the contact condition and the interface characteristics influence the dam behavior. Low shear resistance of interface engenders an increase of relative displacements, settlements, and shear strains in the dam. Moreover, the dilative behavior of the interfaces also affects the overall dam behavior. [ABSTRACT FROM AUTHOR]

The surveillance of a 94.5 m high embankment dam in northern Quebec, Canada, revealed the possibility of the existence of a zone of higher hydraulic conductivity in its till core. The spatial continuity of the measured fines content in the dam during construction was computed by geostatistical means to predict values at unsampled locations for the entire core volume. The hydraulic conductivities were inferred using the predicted fines content and in situ compaction conditions. The inferred hydraulic conductivities and their spatial representations were supported by thermal and seepage field monitoring data. This provided the necessary background information to interpret the surveillance data and determine the cause of the presence of a more pervious zone in the core, which was related to spatial variability of the fines content of the till, placement water content, and compaction procedures. The geostatistical approach complemented with laboratory and construction control data is an efficient tool to characterize dam heterogeneities permitting location of zones of more intensive seepage. [ABSTRACT FROM AUTHOR]

This paper examines the influence of several freeze-thaw cycles on the hydraulic conductivity changes of a glacial till from Péribonka in Quebec, Canada. Samples reconstituted by consolidation of a slurry and by compaction at dry of optimum conditions were subjected to closed freezing and thaw as well as constant-head permeability tests. For saturated consolidated samples, the relationship between the logarithm of hydraulic conductivity and void ratio was linear for both unfrozen and thawed states. At a given void ratio, the increase of the hydraulic conductivity of the thawed soil was larger for compacted and unsaturated samples than for saturated consolidated samples. Actual freeze-thaw-induced hydraulic conductivity changes, however, may be offset by a decrease in void ratio during thaw consolidation. A general framework considering void ratio, water content, stress and hydraulic conductivity relationships is presented for Péribonka glacial till. [ABSTRACT FROM AUTHOR]

Ramped-freezing tests were conducted on three base-course materials with fines contents of less than 7% and compacted at different initial states but always at degrees of saturation near or well below 60%. Three different quarries were studied. The natural fines from crushed gneiss with biotite, limestone, and monzonite were all frost susceptible. Frost heave was relatively small, but significant water intake occurred in all samples during freezing with access to an external water source, regardless of initial saturation level. The frost susceptibility of coarse-grained soils cannot be solely evaluated with respect to frost heave but needs also to consider the amount of water drawn to the freezing front during the freezing process and the consequences of this water during thaw. The normalized heave of the base-course layer of pavements is a practical and efficient indicator of the frost susceptibility of the base-course aggregates. If it is larger than 1%, the base-course material can be considered as frost susceptible leading to a significant increase in the degree of saturation once frozen. Current base-course material specifications based solely on grain-size distribution are not adequate to differentiate materials that are nonfrost susceptible from those that are frost susceptible. Hence, an additional criterion based on the fines frost susceptibility should be considered. Des essais « ramped-freezing ont été réalisés sur trois matériaux de fondation avec moins de 7 % de particules fines compactées à différents états initiaux mais toujours à des degrés de saturation près ou bien en dessous de 60 %. On a étudié trois carrières différentes. Les fines naturelles provenant du gneiss broyé avec de la biotite, du calcaire et de la monzonite étaient toutes susceptibles au gel. Le soulèvement dûau gel était relativement faible mais une absorption d’eau significative s’est produite dans tous les échantillons durant le gel avec un accès à une source extérieure d’eau quelque soit le niveau initial de saturation. La susceptibilité au gel des sols à gros grains ne peut pas être évaluée seulement en fonction du soulèvement dûau gel, mais elle requiert aussi de prendre en considération la quantité d’eau entraînée vers le front de gel durant le processus de gel et ses conséquences durant la fonte. Le soulèvement normalisé de la couche de fondation des chaussées est un indicateur pratique et efficace de la susceptibilité au gel des agrégats des fondations. Si le soulèvement est de plus de 1 %, le matériau de fondation peut être considéré comme étant susceptible au gel, ce qui conduit à une augmentation significative du degré de saturation lorsque gelé. Les spécifications courantes des matériaux de fondation de chaussées basées seulement sur la granulométrie ne sont pas adéquates pour différencier les matériaux qui sont non susceptibles au gel de ceux qui sont susceptibles au gel. D’où, l’on devrait considérer un critère additionnel basé sur la susceptibilité au gel des particules fines. [ABSTRACT FROM AUTHOR]

Heat carried by the seepage water along hydraulic flow lines can serve as a natural tracer to help detect contrasting hydraulic conductivities in embankment dams. Thermal monitoring was realized on the 94.5 m high QA-01 embankment dam in northern Quebec to characterize the temperature distribution across its entire section. The analysis of the annual thermal response of the dam clearly showed a zone of higher seepage velocities in the compacted till core. Approximations concerning the increased hydraulic conductivity were made using a simple thermal model. Complementary numerical modelling provided a more rigorous quantitative assessment of the seepage patterns. The calculations have shown hydraulic conductivities that are 20 times larger than the expected values. Thermal monitoring can detect zones of increased seepage, which can be related to internal erosion or other factors, such as the variability of the soil properties due to construction practices. Temperature measurements alone are not adequate to determine the cause of a permeable zone in a dam or to predict its possible evolution. [ABSTRACT FROM AUTHOR]

A recently developed nonlinear elastic model of granular material, referred to as the tangent modulus – vertical stress (Et–σv) model, was implemented into a finite element numerical solver FlexPDE. The FlexPDE program was used to compare deflection predictions with actual plate-load test data from a site near Québec City. The proposed Et–σv model performed well and led to excellent predictions for load levels of 40, 50, and 70 kN. Comparison with predictions using the Uzan model suggests that constitutive models of granular materials are best expressed in terms of vertical stress rather than mean stress for the prediction of elastic pavement response for field conditions. [ABSTRACT FROM AUTHOR]

Repeated-load triaxial tests were conducted on crushed granitic base-course material to study the resilient response under different stress paths and compaction states. It has been established that the resilient response of this prestrained unbound granular material is best defined in terms of tangent stiffness (Et) and vertical stress (σv). The data also revealed the existence of a threshold value of tangent stiffness that is essentially dependent on initial confining stress for a given compaction state. When the tangent modulus exceeds this threshold value, a unique relationship between tangent stiffness and vertical stress exists for mobilized shear resistance ratios less than 0.4. This Et–σv relationship is independent of stress path. A simple power law model can be used to predict the resilient response of unbound base-course material and an approximate value of resilient modulus for any desired stress path and initial stress condition. The use of the tangent stiffness – vertical stress model for pavement design appears to be very promising. [ABSTRACT FROM AUTHOR]

The limit state characteristics of base-course granular materials were obtained using a typical triaxial testing equipment devoted to the measurement of resilient modulus. Accurate monitoring of axial strain during isotropic and anisotropic compression was used to determine the stress conditions where significant irrecoverable strains occur for samples prepared by static compression, Proctor rammer, and vibratory compaction. The limit state curve is highly anisotropic, centered about the q/p=1 line. It is sensitive to sample preparation technique and fines content. The Strategic Highway Research Program (SHRP) procedure corresponds to stress paths during conditioning and repeated loading that remain within the limit state curve of the control base course material containing 3.5% fines. The resilient modulus values reflect henceforth the behaviour of the same material with its original particle contact distribution. The Laboratoires des Ponts et Chaussées (LCPC) procedure is characterized by stress paths that cross the original limit state curve of the Proctor compacted samples. Particle contact distribution changes thus continuously as the limit state curve expands in response to the various stress paths used in this procedure. The resilient modulus values correspond to samples with different fabrics. A simple procedure based on isotropic loading has been proposed for the determination of a simplified limit state curve of base course materials with the intent of specifying the testing conditions for obtaining adequate resilient modulus values. [ABSTRACT FROM AUTHOR]

The influence of fines on the frost susceptibility of base-course crushed aggregates was established by laboratory freezing tests simulating closely the thermal conditions in the field. The frost susceptibility of the fines was varied by use of different mixtures of granitic fines and commercially available kaolinite clay. A total of 13 samples with fines content of 5%, 10%, and 15% and kaolinite fractions of 10%, 50%, 75%, and 100% were subjected to four freeze–thaw cycles. The frost susceptibility of well-graded crushed aggregates increases with increasing fines content and increasing kaolinite fraction. From a quantitative point of view, for a given kaolinite fraction, the segregation potential increases linearly with fines content, until the fines create a matrix in which the coarser particles are embedded. For the material studied, this occurs when the fines content is higher than 15%. For a given fines content, it was also established that the segregation potential increases linearly with kaolinite fraction, indicating the importance of mineralogy. It was also established that appropriate thermal testing conditions need to be adopted to prevent undue pore water extraction from the unfrozen soil close to the frost front during laboratory freezing of unsaturated coarse-grained soils. [ABSTRACT FROM AUTHOR]

Shallow slides in cohesionless till occurred in several highway fills in the province of Quebec, Canada, following spring thaw and sometimes during rainy autumns. This study has shown that the strength parameters of cohesionless tills can be related to the liquid limit for both drained and undrained conditions. These relationships can be used as input in stability analyses to readily yield design values of stable slopes. Tills with liquid limits between 15% and 25% are all very susceptible to liquefaction flow failures if loosely compacted and saturated. To reduce the risk of shallow slides in the cohesionless till embankments used for highways, a stabilizing coarse-grained fill placed atop of the till embankment appears to be an efficient technique. Design charts of minimum thickness of the stabilizing fill at the base of the till slope were developed using available stability programs and an empirically derived strength of liquefied tills. [ABSTRACT FROM AUTHOR]

This paper presents the results of a thermomechanical simulation of freezing around an existing tunnel in Kobe (Japan) to predict the deformations associated with ice lens formation and those resulting from thaw after construction is completed. The frost heave characteristics used in the numerical model were obtained from laboratory freezing tests conducted on undisturbed samples provided by the Osaka Soil Test Laboratory. With the planned construction schedule, the predictions suggest a maximum frost heave at the ground surface of about 4.8 cm while the expected thaw settlement in the tunnel's centerline was about 13 cm. Observed frost penetration and surface frost heave movements agree well with the predictions. Grout injected during thaw was successful in preventing excessive thaw settlement.Key words: frost, soils, heave, model, monitoring, field.Cet article présente les résultats d'une simulation thermo-mécanique du gel autour d'un tunnel existant à Kobe, Japon, pour prédire les déformations associées à la formation de lentilles de glace et celles résultant du dégel après que la construction eut été complétée. Les caractéristiques de soulèvement dû au gel utilisées dans le modèle numérique ont été obtenues par des essais de gel en laboratoire sur des échantillons non remaniés fournis par le Osaka Soil Test Laboratory. Avec la séquence prévue de la construction, les prédictions suggèrent un soulèvement maximum dû au gel au niveau du sol d'environ 4,8 cm alors que le tassement prévu dû au dégel dans la ligne de centre du tunnel était d'environ 13 cm. La pénétration de gel observée et les mouvements de soulèvement dû au gel sont en bonne concordance avec les prédictions. L'injection durant le dégel a réussi à prévenir le tassement excessif dû au dégel.Mots clés : gel, sol, soulèvement, modèle, mesure, terrrain.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

This paper presents the results of a field study of hoarfrost formation on insulated test sections located in Québec City. It was established that the surface cooling rate increases sharply when all of the granular material placed above the insulating layer is frozen. The absence of latent heat release makes the pavement surface more sensitive to rapidly changing meteorological conditions. It was also shown that hoarfrost formation occurs when the surface temperature is less than the frost point, and it is not related to the dew point, as generally accepted. The paper also discusses the relationship between the hoarfrost index, HFI, and the total thickness of hoarfrost deposits.Key words: frost penetration, pavement, insulation, surface cooling, differential icing, hoarfrost.Cet article présente les résultats d'une étude sur le terrain de la formation de givre sur des sections d'essais de routes isolées dans la Ville de Québec. On a établi que la vitesse de refroidissement de la surface augmente brusquement lorsque tout le matériau granulaire placé au-dessus de la couche d'isolation est gelé. L'absence d'apport de chaleur latente rend la surface du pavage plus sensible aux conditions météorologiques rapidement changeantes. Il a aussi été démontré que la formation de givre se produit lorsque la température de la surface est inférieure au point de gel et n'est pas reliée au point de rosée tel que généralement accepté. L'article discute également de la relation entre l'indice de givre, HFI, et l'épaisseur totale des dépôts de givre.Mots clés : pénétration du gel, pavage, isolation, refroidissement de la surface, glaçage différentiel, givre. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive field investigation of several instrumented road sections in the Province of Quebec, Canada. Falling-weight deflectometer tests, static load tests on embedded plates at different depths, large dynamic cone penetration (DCP) tests, and piezocone tests (CPTU) were performed to study the mechanical response of the pavement. A correlation between elastic deformation modulus inferred from the plate load tests and DCP penetration index was obtained for nine different sites. A correlation between the equivalent elastic modulus of uniform subgrade soils and piezocone tip resistance was also established using data from the falling-weight deflectometer. A procedure for calculating the deflection basin for any pavement system placed over a more complex subgrade stratigraphy was proposed using these correlations. The proposed procedure was validated on two sites and its performance was adequate, since the calculated deflection basins agreed well with the measured deflection basins.Key words: penetration test, piezocone, deflection, pavement, in situ.Cet article présente les résultats d'une étude élaborée sur le terrain de plusieurs sections de route instrumentées dans la Province de Québec, Canada. Des essais au déflectomètre à masse tombante, de chargement statique sur des plaques enfouies à différentes profondeurs, de pénétration dynamique d'un gros cône (DCP), et de piézocône (CPTU) ont été réalisés pour étudier la réponse mécanique de la chaussée. Une corrélation entre le module de déformation élastique déduit des essais de chargement de plaques et l'indice de pénétration DCP a été obtenue pour neuf sites différents. Une corrélation entre le module élastique équivalent des sols de fondations uniformes et la résistance en pointe du piézocône a aussi été établie au moyen des données du déflectomètre à masse tombante. En partant de ces corrélations, on a proposé une procédure pour calculer le bassin de déflexion pour n'importe quel système de chaussée reposant sur une stratigraphie d'infrastructure complexe. La procédure proposée a été validée sur deux sites et sa performance a été adéquate puisque les bassins de déflexion calculés concordaient bien avec les valeurs mesurées.Mots clés : essai de pénétration, piézocône, déflexion, chaussée, in situ.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]