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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.)

Wind turbines are typically designed based on fatigue and serviceability limit states, but still require an accurate assessment of bearing capacity. Overconsolidated clay deposits in Canada often have a thin layer of crust with a relatively high undrained shear strength. However, existing bearing capacity design methods do not consider surficial crusts. This paper studies the undrained VHMT (vertical, horizontal, moment, and torsional) failure envelope of circular foundations founded on a surficial crust underlain by a uniform soil using finite element analysis. Crust correction factors have been introduced to account for the effects of the stiff layer on the vertical and moment capacities. The same forms of equation that are used for uniform soils, but with different parameters provide satisfactory fits for the failure envelopes for a soil with a crustal layer. An analytical expression for the 4-D VHMT failure envelope is derived, and an application of this method is provided. [ABSTRACT FROM AUTHOR]

Landslides involving sensitive clays are recurrent events in the world's northern regions and are especially notorious in eastern Canada. The two critical factors that separate sensitive clay landslides from traditional slope stability analysis are the highly brittle behavior in undrained conditions (strain-softening) characteristic of progressive or retrogressive failures and the large deformations associated with them. Conventional limit equilibrium analysis has numerous shortcomings in incorporating these characteristics when assessing landslides in sensitive clays. This paper presents an extensive literature review of the failure mechanics characteristics of landslides in sensitive clays and the existing constitutive models and numerical tools to analyze such slopes' stability and post-failure behavior. The advantages and shortcomings of the different techniques to incorporate strain-softening and large deformation in the numerical modeling of sensitive clay landslides are assessed. The literature review depicts that elastoviscoplastic soil models with non-linear strain-softening laws and rate effects represent the material behavior of sensitive clays. Though several numerical models have been proposed to analyze post-failure runouts, the amount of work performed in line with sensitive clay landslides is very scarce. That creates an urgent need to apply and further develop advanced numerical tools for better understanding and predicting these catastrophic events. [ABSTRACT FROM AUTHOR]

This paper presents a geotechnical study of a Champlain Sea clay landslide at Breckenridge, Quebec, Canada. Previous studies have interpreted the landslide as triggered by an earthquake occurred about 1020 cal years BP. The current study is to estimate the minimum ground acceleration required to trigger the landslide as part of an effort to further understand the earthquake. The study consists of field and laboratory testing and slope stability analysis. Considerable evidences are presented to understand the slope failure mechanism. The result indicates a minimum horizontal ground acceleration of 0.28 g occurred at the site. Most importantly, the paper provides a case history for better understanding landslide hazards associated with sensitive clay failures in the region. Particularly, the study finds that the landslide is a "flake" type failure as opposed to a retrogressive failure commonly perceived for Champlain Sea clay landslides. It brings to light the "flake" slide as an important factor to consider for improvement of the current predictive models for sensitive clay failures. It also shows that earthquake-triggered "flake" slide can be much larger than retrogressive failures in the same settings. The case history may therefore help as a reference for improved mitigative measures. [ABSTRACT FROM AUTHOR]

Sensitive clay subjected to cyclic loading may experience gradual loss of its shear strength, which may lead to liquefaction. Foundations built on this clay would suffer extensive settlement and significant loss of bearing capacity or perhaps catastrophic failure. This paper presents an experimental investigation on sensitive (Champlain) clay obtained from the city of Rigaud, Quebec (Canada). Consolidation tests, static and cyclic undrained and drained triaxial tests were performed on representative samples of this clay. The objective of this investigation was to examine the influence of the physical and mechanical parameters, which govern the shear strength of sensitive clay subjected to cyclic loading. Based on the results of the present investigation and those available in the literature, it can be reported herein that the undrained response is the most critical for these foundations; furthermore, the preconsolidation pressure is considered as an important parameter in establishing the shear strength of sensitive clay. A design procedure is developed to determine the safe zone for the undrained and drained responses, within which a combination of the cyclic deviator stress and the number of cycles for a given soil/loading/site conditions can achieve a quasielastic resilient state without reaching failure. The proposed design procedure is applicable to all regions around the world, where sensitive clays can be found. Furthermore, this procedure can be adopted to examine the conditions of existing foundations built on sensitive clay at any time during its lifespan. [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 Bulletin of Engineering Geology & the Environment is the property of Springer Nature 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.)

Several oil sands mines and refineries are currently recovering oil from the Athabasca River region near Fort McMurray, Alberta. Planning and construction of additional oil sands mines are in various stages of completion. Due to environmental concerns for aquatic life in areas downstream from current and future oil sands activities, surveys were conducted between 1998 and 2000 to determine whether the quality of water and sediments in tributaries of the Athabasca River are affected by flowing through reaches with exposure to natural oil sand deposits. This paper presents the results for metals in bed and suspended sediments collected from the Mackay, Steepbank, and Ells rivers during those surveys. The suspended sediments had a clay content (n = 7) ranging from 36.2% to 65.0%, while bed sediments, which consisted of a predominant sand fraction, had percent clay (n = 39) ranging from 0.0% to 38.1%. A Mann-Kendall non-parametric analysis to assess the longitudinal trend of the metals in the bed sediments found no significant (α = 0.05) downstream trend in the Mackay or Steepbank rivers; however, the Ells River displayed a generally decreasing tend from upstream to downstream. The results provide no indication that metal concentrations in the bed sediments and/or suspended sediments of the Mackay, Steepbank, and Ells rivers increase significantly as the three tributaries flow through reaches that have natural oil sand exposures (McMurray Formation). [ABSTRACT FROM AUTHOR]

Unlike typical soils, sensitive clays undergo extensive post-peak strength degradation with increasing strain and finally disintegrate into a remolded liquid state. Realization of post-peak stress-strain behavior of sensitive clay up to large strains is vital in assessing large deformation problems such as landslides and mud flows. The conventional experimental approaches are uncertain about accurately determining the post-peak stress curve up to large strains (>100%) owing to rapidly increasing testing problems at increasing strains. This necessitates the exploration of an alternative scientific approach to predict the complete stress-strain curve for sensitive clays, which is addressed in this paper. Post-peak stress-strain curves of sensitive clays for different sites are obtained by converting remolding index vs. strain energy curves. Using site-specific data from eastern Canada sites, a mathematical expression is proposed to predict the complete stress-strain curve. Subsequently, an equation is developed for predicting remolding energy based on the stress-strain curve. Finally, it is observed that the post-peak stress-strain behavior is highly site-specific and can be mathematically expressed with a combination of exponential and linear strain-softening curves. Overall, the knowledge of the complete stress-strain behavior contributes greatly to the prediction of post-failure movements closer to reality. • Determination of complete post-peak behavior of sensitive clays up to remolding. • Limitations of the generalized application of existing strain softening equation. • The proposition of a new site-specific strain softening equation with its application in some real-case scenarios. • The proposition for an equation to determine remolding energy as well as an equation to estimate the retrogression distance. [ABSTRACT FROM AUTHOR]

The preconsolidation pressure and overconsolidation ratio profiles are the most important factors related to the mechanical behaviour of clay deposits. They are interpreted on the basis of a limited number of laboratory tests, but the near-continuous information provided by the piezocone can allow local data to be extrapolated to an entire site. Numerous methods have been proposed for relating piezocone data to preconsolidation pressure and the overconsolidation ratio, but their validity is still uncertain. In this paper, nine methods are compared on the basis of data collected on 31 sensitive clay sites in Quebec whose preconsolidation pressure profiles are well known. Each method is briefly presented and the most promising are identified. The simplest method, which directly relates preconsolidation pressure to net tip resistance, also appears to be the most effective.Key words: clay, preconsolidation pressure, overconsolidation ratio, piezocone, correlations.Les profils de pression de préconsolidation et du rapport de surconsolidation constituent les éléments les plus importants en ce qui concerne le comportement mécanique des dépôts argileux. Leur évaluation se fait par un nombre limité d'essais de laboratoire, mais les données fournies par le piézocône de manière presque continue peuvent permettre une extrapolation à l'ensemble du site de ces données locales. De nombreuses méthodes ont été proposées pour corréler les données du piézocône et la pression de préconsolidation ou le rapport de surconsolidation mais leur validité est encore incertaine. Dans le présent article, neuf méthodes sont examinées à partir de données provenant de 31 sites d'argile sensible de la province du Québec pour lesquels les profils de pression de préconsolidation sont bien connus. Chaque méthode est brièvement présentée et les méthodes les plus intéressantes sont identifiées. Il semble que la relation entre la pression de préconsolidation et la résistance en pointe nette, qui est la plus simple, est aussi la plus efficace.Mots clés : argile, pression de préconsolidation, rapport de surconsolidation, piézocône, corrélations. [ABSTRACT FROM AUTHOR]

To analyze the effects of strain rate and viscoplastic strain on consolidation of natural clay, this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a unique effective stress (σ'[sub v] ) – viscous strain (ℇ[sub v] ) – viscous strain rate (ℇ[sup ·] [sub v] ) relationship. The proposed model can consider the effects of strain rate and viscoplastic strain on consolidation, to take into account the difference in strain rate between laboratory and field conditions, and the combined processes of generation and dissipation of pore pressure during consolidation. This model can also predict the behaviour of clay during stepwise loading, constant rate of strain, and relaxation of effective stress. The predicted values using numerical analysis are compared with measured values in laboratory tests and in situ, under an embankment built on soft clay at Berthierville, Quebec. It is possible to estimate the consolidation behaviour of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.Key words: consolidation, soft clay, strain rate, viscoplastic, relaxation.Dans le but d'analyser les effets de la vitesse de déformation et de la déformation viscoplastique sur la consolidation de l'argile naturelle, cet article présente un modèle viscoplastique non linéaire dans lequel le comportement est modélisé par une relation unique contrainte effective-déformation visqueuse-vitesse de déformation visqueuse σ'[sub v] – ℇ[sub v] – ℇ[sup ·] [sub v] . Le modèle proposé peut prendre en considération les effets de la vitesse de déformation et de la déformation viscoplastique sur la consolidation pour tenir compte de la différence dans les vitesses de déformation entre les conditions en laboratoire et sur le chantier, de même que les processus combinés de génération et de dissipation de la pression interstitielle durant la consolidation. Ce modèle peut aussi prédire le comportement de l'argile en incluant le chargement par étape, la vitesse de déformation constante, et la relaxation de la contrainte effective. Les valeurs prédites au moyen de l'analyse numérique sont comparées avec celles mesurées dans les essais en laboratoire et in situ sous un remblai construit sur de l'argile molle à Berthierville, Québec. Il est possible d'estimer le comportement en consolidation de l'argile naturelle avec une précision raisonnable au moyen du modèle viscoplastique non linéaire proposé. Mots clés : consolidation, argile molle, vitesse de déformation, viscoplastique, relaxation.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

This study investigated a new predictive model of the shear modulus reduction ( G G max − Log (γ c)) and damping ratio (ξ − Log (γc)) curves for sensitive eastern Canada clays. The model was established based on experimental measurements of G G max and ξ performed on 69 sensitive clay specimens from eastern Canada. The compiled database was first analyzed to qualitatively assess the influences of different soil parameters on the measurements. Next, statistical analyses using regression analysis and the modified hyperbolic model were performed. It was found that the G G max and ξ values of sensitive eastern Canada clays were influenced mainly by the plasticity index (Ip), mean effective stress (σ m ′) , and structure, which was quantified by the liquidity index (IL). Based on the statistical analysis performed, new equations for G G max and ξ were proposed. The newly proposed model was compared with previously published models. The comparison clearly showed that the proposed model was more representative of sensitive eastern Canada clays. Consequently, it is suggested that the proposed model is more appropriate for use in the dynamic analysis of sensitive eastern Canada clay deposits as well as other similar soils. [ABSTRACT FROM AUTHOR]

Due to inherent variability arising from unpredictable geological depositional and post-depositional processes, the geotechnical parameters of Laflamme sea clay deposits remain highly uncertain. This study aims to develop and apply a methodology to assess the uncertainties of geotechnical parameters using statistical distributions for a landslide-prone Saguenay Lac-Saint-Jean (SLSJ) region. We used the measured physical and mechanical parameters of Laflamme Sea clays of various locations in the SLSJ region to characterize the geotechnical parameters in a representative manner. Goodness-of-fit tests assign each physical and mechanical parameter a distribution function for their descriptive analysis. We found that the quality of these tests is significantly influenced by outliers. The detected outliers in the dataset considerably impact the distribution type and the uncertainties of the specific geotechnical parameter. Subsequently, appropriate distribution functions for each parameter were assigned after treating the outliers. The derived coefficient of variability values for the SLSJ region were significantly high in comparison to the literature with cone penetration test data being only the exception. Finally, the results indicated that the uncertainties of geotechnical parameters of the Saguenay-Lac-Saint-Jean region marine clays are high as compared to Scandinavian clays and are relatively comparable to other eastern Canadian clays. [ABSTRACT FROM AUTHOR]

The Tunnel Sealing Experiment (TSX) was an international project developed by Canada, Japan, France, and the United States. The TSX consisted of a clay bulkhead and a concrete bulkhead. The two bulkheads were at opposite ends of a 12-m-long sand-filled chamber. The heating phase involved the circulation of heated water through the TSX chamber to raise the temperature of the sealing system. This was done to evaluate the influence of elevated temperature on the performance of the bulkheads. Numerical analyses to simulate the thermohydromechanical evolution of the clay bulkhead and the surrounding rock of the TSX were performed using MOTIF finite-element program and compared with measured data. This paper focuses on a preliminary interpretation of the results from the fully coupled thermohydromechanical modeling of the clay bulkhead and the adjacent rock during heating. Discussion of the issues that will affect the ability to model a field application is provided in the course of comparing simulated and measured results. [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.)

Presents the results of a comparative study of pockmark sediments and associated features appearing on both sides of the North Atlantic, on the Scotian Shelf off Nova Scotia and in the northern North Sea. Formation in seabed material consisting of soft silty clay; Seismic, sonar and lithologic characteristics of the sediments; Gas efflux through the seafloor.

Anisotropic behaviour of the clay core, blanket, and foundation of aging water retaining earth fill dams on glacio-lacustrine clay deposits in Canada may be a result of environmental loading. The repeated wetting-drying and freezing-thawing cycles produce fissures that can cause degradation of strength with time. Undisturbed clay samples taken from field investigations of an existing aging water retaining earth fill dam were tested in the laboratory to obtain the parameters used in the numerical modeling. A testing program was implemented in order to determine the basic soil properties along with mineralogy, strength, and deformation characteristics of the collected clay samples. Laboratory tests include index property tests, Scanning Electron Microscopy (SEM) tests, X-Ray Diffraction (XRD) tests, one-dimensional consolidation oedometer tests, consolidated drained direct shear tests, and isotropically consolidated undrained triaxial compression tests. Results revealed that the clay samples from the clay core, blanket and foundation were similar in terms of structural and mineralogical composition. The observed interlayered smectite and illite indicated that the micro fabric was anisotropic. Strength anisotropy was noticed as results had different cross shear and horizontal shear strength values. Numerical modeling was performed to assess the slope stability of an aging earth dam that experienced sliding movements using parameters from the completed laboratory investigation. Findings from slope stability analyses indicated that a better representation of the observed site conditions was evident when strength anisotropy was considered. [ABSTRACT FROM AUTHOR]

Paleoclimatic data from a sequence of argillite deposits of the Gowganda Formation located in the Mississagi River Valley (southern Ontario Province, Canada) covering a time interval of 256 years with a time resolution of one year are studied to research possible variations of the Earth's climate in the Paleoproterozoic (~2 Ga ago). The following quasi-periodic variations have been found via the construction of a combined spectral periodogram: 3, 5, 11, 14, 29, and 75 years (at significance levels of the respective estimated values of magnitudes ranging from 2σ to 4σ). This may indicate the possible influence of solar activity on climate changes in the geological past. [ABSTRACT FROM AUTHOR]

Pedotransfer functions (PTFs) are empirical fits to soil property data and have been used as an alternative tool to in situ measurements for estimating soil hydraulic properties for the last few decades. PTFs of Saxton and Rawls, 2006 (PTFs'S&R.2006) are some of the most widely used because of their global aspect. However, empirical functions yield more accurate results when trained locally. This study proposes a set of agricultural PTFs developed for southern Quebec, Canada for three horizons (A, B, and C). Four response variables (bulk density (ρb), saturated hydraulic conductivity (Ksat), volumetric water content at field capacity (θ33), and permanent wilting point (θ1500)) and four predictors (clay, silt, organic carbon, and coarse fragment percentages) were used in this modeling process. The new PTFs were trained using the stepwise forward regression (SFR) and canonical correlation analysis (CCA) algorithms. The CCA- and SFR-PTFs were in most cases more accurate. Θ1500 and at θ33 estimates were improved with the SFR. The ρb in the A horizon was moderately estimated by the PTFs'S&R.2006, while the CCA- and SFR-PTFs performed equally well for the B and C horizons, yet qualified weak. However, for all PTFs for all horizons, Ksat estimates were unacceptable. Estimation of ρb and Ksat could be improved by considering other morphological predictors (soil structure, drainage information, etc.). [ABSTRACT FROM AUTHOR]

Four different seismic methods were used extensively to evaluate the shear wave velocity of soils and rock in the city of Ottawa, Canada, from which the travel-time weighted average shear wave velocity (Vs) from surface to 30 m in depth (Vs30) and the fundamental frequency (F0) were computed. Three main geological or geotechnical units were identified with distinct shear wave velocities: these consist of very loose thick post-glacial fine-grained sands, silts, and clays (Vs <150 m/s, thickness up to 110 m), firm glacial sediments (Vs ~580 m/s, thickness ~3 m), and very firm bedrock (Vs ~1750-3550 m/s). The seismic methods applied were downhole interval Vs measurements at 15 borehole sites, seismic refraction-reflection profile measurements for 686 sites, high-resolution shear wave reflection 'landstreamer' profiling for 25 km in total, and horizontal-to-vertical spectral ratio (HVSR) of ambient seismic noise to evaluate the fundamental frequency for ~400 sites. Most of these methods are able to distinguish the very high shear wave impedance of and depth to bedrock. Sparse earthquake recordings show that the soil amplification is large for weak motion when the soil behaves linearly. Quatre méthodes sismiques différentes ont été grandement utilisées afin d'évaluer la vitesse des ondes de cisaillement des sols et roches dans la ville d'Ottawa, Canada, à partir desquelles la vitesse moyenne des ondes de cisaillement pondérée selon le temps de parcours (Vs) de la surface jusqu'à une profondeur de 30 m (Vs30) et la fréquence fondamentale (F0) ont été calculées. Trois unités géologiques ou géotechniques principales ont été identifiées selon des vitesses des ondes de cisaillement distinctes : des sables, silts et argiles post-glaciaires fins, lâches et épais (Vs <150 m/s, jusqu'à 110 m d'épaisseur), des sédiments glaciaires fermes (Vs ~580 m/s, ~3 m d'épaisseur) et du substratum rocheux très ferme (Vs ~1750-3550 m/s). Les méthodes sismiques appliquées étaient des mesures de Vs par intervalle en fond de forage pour 15 sites de forage, des mesures du profil de réfraction-réflexion sismique pour 686 sites, du profilage de la réflexion des ondes de cisaillement à haute résolution « landstreamer » pour 25 km linéaire au total, et le ratio spectral horizontal-vertical (RSHV) du bruit sismique ambiant pour l'évaluation de la fréquence fondamentale sur environ 400 sites. La majorité de ces méthodes sont capables de distinguer l'impédance très élevée aux ondes de cisaillement et la profondeur jusqu'au substratum rocheux. Quelques mesures de séismes montrent que l'amplification du sol est grande pour des mouvements faibles lorsque le sol de comporte de façon linéaire. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature 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.)

Investigates the mechanism of erosion and the factors influencing erosion rates of clay banks of the Saint Lawrence River along the Montréal to Lac Saint Pierre n Quebec. Literature review; Details on the experiments; Results of the study; Conclusions.

Two large-scale sealing experiments were conducted at Atomic Energy of Canada Limited's Underground Research Laboratory at Lac du Bonnet, Manitoba. The rate of water uptake in densely compacted sand–clay buffer materials proposed for use in a deep geologic repository for spent nuclear fuel was monitored. The buffer–container experiment examined the influence of heat on the performance of a large mass of buffer. Temperatures, water contents, and total and hydraulic pressures within and surrounding the installation were monitored for approximately 2.5 years. Local groundwater pressures increased as a result of rising temperatures. Water uptake and redistribution occurred in the buffer due to drying shrinkage close to the heater and counter-acted swelling due to an increase in water content near the rock–buffer interface. The isothermal test (ITT) allowed natural groundwater uptake from the surrounding rock mass under isothermal conditions. It was monitored for a period of 6.5 years and is the first, and longest running test of its kind yet conducted in the world. During its operation, the ITT (for as yet unconfirmed reasons) experienced a 35% decrease in the rate of water supply relative to that measured prior to experiment installation. This decrease impacts on the time required for saturation to be achieved.Key words: buffer, bentonite, underground research laboratory, instrumentation.Deux essais d'étanchéité à grande échelle ont été conduits au Laboratoire de recherche souterrain de l'Énergie atomique du Canada au lac du Bonnet, Manitoba. On a mesuré la vitesse d'absorption d'eau dans des matériaux tampons formés de sable et argile densément compacts devant être utilisés dans un dépôt géologique profond pour le combustible nucléaire irradié. L'expérience tampon–conteneur a permis d'examiner l'influence de la chaleur sur la performance d'une large masse de tampon. Les températures, teneurs en eau, pressions totales et hydrauliques à l'intérieur et autour de l'installation ont été mesurées durant environ 2,5 années. Les pressions de l'eau souterraine locale ont augmenté à cause de l'augmentation de la température, une absorption et une redistribution se sont produites dans le tampon à cause du séchage et du retrait près des points chauds d'une part, et de l'action inverse du gonflement dû à l'augmentation de la teneur en eau près de l'interface roc–tampon d'autre part. L'essai isothermique a permis l'absorption de l'eau souterraine naturelle venant du massif rocheux dans des conditions isothermiques. Des mesures ont été prises durant une période de 6,5 années, et cet essai est le premier et le plus long essai de ce type à être réalisé jusqu'à ce jour dans le monde. Au cours de son opération, cet essai a subi, pour des raisons encore non confirmées, une diminution de 35 % de la vitesse de son alimentation en eau par rapport à celle mesurée avant la mise en place de l'expérience. Ceci a des impacts sur le temps requis pour atteindre la saturation.Mots clés : tampon, bentonite, Laboratoire de recherche souterrain, instrumentation.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Two large landslides in overconsolidated glaciolacustrine clay and silt, located in river valleys in British Columbia, were found to be quite similar in their main aspects. However, their failure behaviour was very different. One continues to exhibit intermittent, mainly ductile deformations with limited mobility which are typical of compound landslides in stiff clay. The other suddenly developed into an extremely rapid flow slide of 6.4 Mm[sup 3] , damming a large river in the course of a few minutes and projecting a wave onto the opposite bank. The flow slide followed a period of strong infiltration. A comparison of the two cases explains the difference in their failure behaviour. Three possible mechanisms for brittle flow slide formation are proposed, the first based on the undrained brittleness of soil at the rupture surface, the second on the high internal strength of the sliding body, and the third on macroscopic brittleness developed by pre-failure ductile deformation and softening. Both latter mechanisms are facilitated by the presence of nonplastic units in the sliding mass.Key words: overconsolidated clay, silt, landslide, flow slide, brittleness, glaciolacustrine deposits.On a observé que deux grands glissements dans les argiles et silts glacio-marins surconsolidés situés dans des vallées de rivières en Colombie-Britannique étaient tout à fait semblables sous leurs principaux aspects. Cependant, leurs comportements en rupture ont été très différents. L'un continue de montrer des déformations intermittentes principalement ductiles avec une mobilité limitée, ce qui est typique des glissements composés dans les argiles raides. L'autre a soudainement développé une coulée extrêmement rapide de 6,4 Mm[sup 3] , damant une rivière importante en l'espace de quelques minutes et projetant une vague sur la berge opposée. La coulée s'est produite après une période de forte infiltration. Une comparaison des deux cas explique la différence dans leur comportement en rupture. On propose trois mécanismes possibles de formation de coulée: le premier basé sur la fragilité non drainée du sol le long de la surface de rupture, le second sur la forte résistance interne de la masse en mouvement, et le troisième sur la fragilité macroscopique développée par une déformation ductile et un ramollissement avant la rupture. Le deux derniers mécanismes sont facilités par la présence d'unités non plastiques dans la masse en mouvement. Mots clés : argile surconsolidée, silt, glissement, coulée, fragilité, dépôts glacio-marins.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

An investigation and remediation of instability along cut slopes of an irrigation canal in salt-rich clayey colluvium in southern Alberta is described. Random sloughing of the canal side slopes began to occur 2 years after construction over a 7500 m length of canal and was nearly continuous over a 2500 m length 3 years later. The sloughs are shallow seated and most had the appearance of a "mud" flow. Soil salinity also developed along the canal slopes due to capillarity and evaporation. Failure of the clay slopes in the cut sections is attributed to swelling, dispersion, and softening of the subgrade due to exposure of the salt-laden clays to fresh water. In contrast, 600 m of salt-rich clayey colluvium compacted as a clay liner on the canal side slopes showed no evidence of sloughing and salt loading after 9 years of service. Good soil compaction inhibited softening and slope instability in these salt-rich soils. Results from detailed site investigations and observations, and the interplay of soil chemistry and geology, facilitated the selection of a satisfactory method of repair. Repairs consisted of reconstructing 2500 m of canal by overexcavating the canal subgrade and replacing those soils with compacted soil.Key words: clays, salts, dispersive, sloughing, salinity, compaction.On présente une étude et un comfortement de l'instabilité le long de pentes excavées d'un canal d'irrigation dans les colluvions argileux riches en sel dans le sud de l'Alberta. Des glissements superficiels aléatoires dans les pentes latérales du canal ont commencé à se produire 2 ans après la construction sur une longueur de 7500 m de canal et étaient quasiment continus sur une longueur de 2500 m après 3 ans. Les surfaces de glissement sont peu profondes, et la plupart avaient une apparence d'écoulements de boue. La salinité du sol s'est accentuée le long des pentes du canal à cause de la capillarité et de l'évaporation. La rupture des pentes argileuses dans les sections excavées est attribuée au gonflement, à la dispersion, et au ramollissement de la fondation par suite de l'exposition à l'eau douce des argiles chargées de sel. Par opposition, 600 m de colluvions argileux riches en sel compactés comme membrane argileuse sur les pentes latérales du canal n'ont montré aucune évidence de glissement de surface et d'absorption de sel après 9 ans de service. Un bon compactage du sol a empêché le ramollissement et l'instabilité de la pente dans ces sols riches en sel. Les résultats des études et observations détaillées du site, et l'interaction de la chimie et de la géologie ont facilité la sélection d'une méthode satisfaisante de réparation. Les réparations ont consisté en la reconstruction de 2500 m de canal par surexcavation de la fondation du canal et le remplacement de ces sols par un sol compacté.Mots clés : argiles, sels, dipersive, glissement de surface, salinité, compactage.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Ceramic water filters (CWFs) are point-of-use drinking water treatment systems that are manufactured and used in under-served communities around the world. The clayey material (CM) used to manufacture CWFs is a locally sourced mixture of clay, sand, slit and amorphous material (usually dug near the CWF factory). CM varies in composition and purity depending on the geographical location and geological setting. In this study, a set of 13 CM samples collected from around the world were analyzed using grain size analysis, as well as liquid and plastic limit tests. Mineralogical composition was determined using X-ray diffraction. A selection of three CM samples (Guatemala, Canada, and Guinea Bissau) with a range of compositions were used to study biofilm growth on CM before and after firing. Biofilm coverage was studied on CM (before firing) and CWF material (after firing) using Pseudomonas fluorescens Migula. The average biofilm coverages for Guatemala, Canada, and Guinea Bissau CM were 20.03 ± 2.80%, 19.28 ± 0.91%, and 9.88 ± 4.02%, respectively. The average biofilm formation coverages for Guatemala, Canada, and Guinea Bissau CWF were 13.08 ± 1.74%, 10.36 ± 3.41%, and 8.66 ± 0.13%, respectively. The results presented here suggest that CM can be manipulated to manufacture better performing CWFs by engineering the soil characteristics, such as grain size, liquid and plastic limits, and mineralogy. This could improve the durability and biofilm resistance of CWFs. [ABSTRACT FROM AUTHOR]