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Vibrating-wire piezometers provide a number of advantages over the traditional hydraulic piezometer design. There are currently many methods and configurations for installing vibrating-wire piezometers, the most common being: single piezometers in sand packs (SP), multilevel piezometers in sand packs (MLSP), and fully grouted multilevel piezometers using either bentonite (FGB) or cement-bentonite grout (FGCB). This study assesses the performance of these four different installation methods at a field site possessing complex stratigraphy, including glacial and marine sediments. To accomplish this objective, pore pressure data recorded between December 2017 and July 2019 were analyzed. Data indicate that SP, MLSP, and FGB piezometers performed most reliably, because piezometers installed at the same depth with these methods recorded similar pressure variations that were coherent with the hydrogeological setting. Of the two fully grouted installations using cement-bentonite grout, one installation failed completely due to a hydraulic short circuit, likely caused by preferential flow occurring along the wires of the embedded instruments. The lack of a standard method for mixing cement-bentonite grout at the time of construction likely contributed to the failure of the FGCB installations, as the grout mixture used in this study was likely too viscous to provide a suitable seal. Key words: vibrating-wire piezometers, St. Lawrence Lowlands, fully grouted methods. Les piezometres a fil vibrant offrent un certain nombre d'avantages par rapport aux piezometres hydrauliques traditionnels. Il y a actuellement de nombreuses methodes et configurations pour installer des piezometres a fil vibrant, les plus courantes etant les suivantes : piezometres simples dans des paquets de sable (SP), piezometres multiniveaux dans des paquets de sable (MLSP) et piezometres multiniveaux entierement scelles a l'aide de bentonite (FGB) ou de coulis de ciment-bentonite (FGCB). Cette etude evalue les performances de ces quatre methodes d'installation differentes sur un site de terrain presentant une stratigraphie complexe, comprenant des sediments glaciaires et marins. Pour atteindre cet objectif, les donnees de pression interstitielle enregistrees entre decembre 2017 et juillet 2019 ont ete analysees. Les donnees indiquent que les piezometres SP, MLSP et FGB ont donne les resultats les plus fiables, car les piezometres installes a la meme profondeur avec ces methodes ont enregistre des variations de pression similaires, coherentes avec le contexte hydrogeologique. Parmi les deux installations entierement scellees a l'aide d'un coulis de ciment-bentonite, l'une d'elles s'est completement effondree en raison d'un courtcircuit hydraulique, probablement cause par un ecoulement preferentiel le long des fils des instruments encastres. L'absence d'une methode standard pour le melange de coulis de ciment-bentonite au moment de la construction a probablement contribue a l'echec des installations de BGCF, car le melange de coulis utilise dans cette etude etait probablement trop visqueux pour assurer une etancheite adequate. [Traduit par la Redaction] Mots-cles : piezometres a fil vibrant, basses terres du Saint-Laurent, methodes a scellement complet., 1. Introduction In the province of Quebec, 89% of the population of the province lives within the depositional extent of the Champlain Sea sediments, which were deposited by a marine [...]

The thick sequences of marine clayey deposits that blanket the St. Lawrence Lowlands in south-eastern Canada are highly susceptible to landslides. With 89% of the population of the province of Quebec living in this region, improving our understanding of the mechanisms causing landslides in these sediments is a matter of public security. To accomplish this goal, instruments were deployed at a field site in Sainte-Anne-de-la-Perade, Quebec, Canada to monitor atmospheric, soil, and groundwater conditions. Field and laboratory measurements of soil geotechnical and hydraulic properties were also performed. Results indicate that the groundwater and pore pressure dynamics at the site cannot be explained using simplified site conceptual models. Further analysis indicates that groundwater dynamics and pore pressures in the massive clay deposits on site are determined by (i) the highly heterogeneous nature of the local geological materials, (ii) the contrasting hydraulic and geotechnical properties of these materials, (iii) the presence of two unconfined aquifers at the site, one surficial and one at depth, and (iv) the presence of the Sainte-Anne River. These results were used to create a new conceptual model that illustrates the complex groundwater flow system present on site and shows the importance of including hydrogeologic context in slope stability analysis. Key words: St. Lawrence Lowlands, slope stability analysis, site characterization, hydrogeology, sensitive clays. Les epaisses sequences de depots argileux marins qui recouvrent les basses terres du Saint-Laurent dans le sud-est du Canada sont tres sensibles aux glissements de terrain. Avec 89 % de la population du Quebec vivant dans cette region, ameliorer notre comprehension des mecanismes a l'origine des glissements de terrain dans ces sediments est une question de securite publique. Pour atteindre cet objectif, des instruments ont ete deployes sur un site d'etude a Sainte-Anne-de-la-Perade, Quebec, Canada, afin de surveiller les conditions de l'atmosphere, du sol et des eaux souterraines. Des mesures sur le terrain et en laboratoire des proprietes geotechniques et hydrauliques du sol ont egalement ete effectuees. Les resultats indiquent que la dynamique des eaux souterraines et de la pression interstitielle sur le site ne peut etre expliquee a l'aide de modeles conceptuels simplifies du site. Une analyse plus approfondie indique que la dynamique des eaux souterraines et les pressions interstitielles dans les depots d'argile massifs sur place sont determinees par (i) la nature hautement heterogene des materiaux geologiques locaux (ii) les proprietes hydrauliques et geotechniques contrastees de ces materiaux, (iii) la presence de deux aquiferes non confines sur le site, l'un en surface et l'autre en profondeur, et (iv), la presence de la riviere Sainte-Anne. Ces resultats ont ete utilises pour creer un nouveau modele conceptuel qui illustre le systeme complexe d'ecoulement des eaux souterraines present sur le site, et montre l'importance d'inclure le contexte hydrogeologique dans l'analyse de la stabilite des pentes. [Traduit par la Redaction] Mots-cles: Basses terres du Saint-Laurent, analyse de la stabilite des pentes, caracterisation du site, hydrogeologie, argiles sensibles., 1. Introduction Landslides in sensitive clays represent one of the largest geological hazards in Eastern Canada (Hungr and Locat 2015; Locat et al. 2017). The St. Lawrence Lowlands, located primarily [...]

The 1889 rock slide along Champlain Street is the one that caused the largest number of fatalities in this area of Quebec City during the 19th century. This paper presents a historical retrospective of the events leading to the 1889 slide, starting with the 1841 slide in the same area, which was as significant. Mitigation measures were initiated mainly after 1880, but they were not sufficient to prevent the major catastrophe anticipated by those who did the investigation of the Cap Diamant, including Charles Baillairge. The story of the 1889 slide ends in 1894 by a judgment by the Supreme Court of Canada, in which the Queen was not held responsible for the consequences of the slide, although the main trigger was the water draining from the Citadel, from a damaged drain, into the cliff fissures. A back-analysis of the 1889 slide reached the same conclusions as Charles Baillairge: the 1889 slide was a topple. This paper also highlights the significant contribution of Charles Baillairge (1826-1906) in the understanding of rock slide processes along Cap Diamant. Le glissement rocheux de 1889 le long de la rue Champlain est celui qui a cause le plus de deces dans cette partie de la ville de Quebec au cours du 19e siecle. Cet article presente une retrospective historique des evenements qui ont mene a celui de 1889, et cela en commencant par un autre glissement rocheux survenu en 1841 dans le meme secteur, evenement aussi important que celui de 1889. Des mesures de prevention ont ete mises en place apres 1880 mais elles n'ont pas ete suffisantes pour prevenir la catastrophe de 1889 qui avait ete apprehendee par ceux, incluant Baillairge en 1880, qui avaient etudie le site du cap Diamant. La revue historique du glissement souligne le jugement de la Cour Supreme du Canada en 1894 qui conclut que la Reine ne pouvait etre tenue responsable des consequences du glissement malgre le fait qu'un drain defectueux aurait permis aux eaux de drainage de la Citadelle de s'infiltrer dans les larges fissures presentes dans le talus. Une retro-analyse du glissement de 1889 a permis d'appuyer le fait que le glissement etait un basculement. Cet article souligne la contribution de Charles Baillairge (1826-1906) a la comprehension des glissements de terrain le long du cap Diamant., Introduction Le promontoire de Quebec, de par sa position strategique le long du fleuve Saint-Laurent, est un des lieux les plus peint et photographie au Canada depuis le XVIIe siecle. [...]

The Black Lake rockslide is located on the east wall of an open-pit mine initially operated by LAB Chrysotile near Thetford Mines, Quebec. Movements were observed in July 2012 when a volume of 2.0 x [10.sup.7] [m.sup.3] was mobilized, destroying a large portion of Highway 112. Mining operations ceased in 2012, causing the complete shutdown of the pumping system whose goal was to prevent the rise of water level in the pit. As the water level increases in the pit, it is essential to determine the potential of tsunami generation by possible partially submerged rockslides and to understand the potential impacts. A series of possible scenarios have been analysed with regard to velocity and acceleration of the potential rockslide as well as the corresponding wave generation and inundation. Results from the simulation show that when the factor of safety of the global slope is less than unity, inundation would not reach the potentially vulnerable infrastructures. Maximum wave height will vary as a function of the filling of the lake, and the lower wave height relative to water depth will happen when the lake is completely filled.Key words: landslide-generated tsunami, partially submerged landslide, numerical modeling, open-pit mine, active rockslide.Le glissement de Black Lake est situe sur la paroi est d'une ancienne mine a ciel ouvert exploitee par la compagnie LAB Chrysotile, a Thetford Mines, Quebec. Ce glissement actif a connu un fort episode de glissements en juillet 2012, ou un volume de 2,0 x [10.sup.7] [m.sup.3] a ete mobilise, emportant une large portion de la Route 112. Les operations minieres ont cesse en 2012, causant l'arret complet du systeme de pompage lequel visait a prevenir la montee du niveau d'eau dans la fosse. Comme le niveau d'eau augmente dans la fosse il devient primordial de determiner le potentiel tsunamigenique genere par des glissements rocheux partiellement submerges possibles afin de comprendre le phenomene et de reagir efficacement a celui-ci. Plusieurs modelisations numeriques ont ete realisees a partir de scenarios probables concernant les vitesses et les accelerations de glissement rocheux potentiel ainsi que la formation de vagues et l'inondation correspondantes. Les modelisations effectuees ont permis de montrer que, lorsque le facteur de securite de la pente globale est inferieur a 1, aucune infrastructure potentiellement vulnerable ne serait touchee par un eventuel tsunami. La hauteur maximale de la vague generee sera fonction de la hauteur d'eau dans le bassin. Les hauteurs de vagues minimales, relatives au niveau d'eau dans le bassin, seront generees lorsque le bassin sera completement rempli.Mots-cles: tsunami genere par un glissement de terrain, glissement partiellement submerge, modelisation numerique, mine a ciel ouvert, glissement rocheux actif., 1. IntroductionApproximately 90 km south of Quebec City, on the border between Black Lake sector to the north (part of Thetford Mines) and the municipality of Saint-Joseph-de-Coleraine to the south, [...]

In recent years, several large open-pit mines have started operating in the province of Quebec in Canada, and some of the largest planned pits are located close to public infrastructure. Historically, large open-pit mining has seldom been done in many mining regions, such as the Abitibi region, where underground mines are the norm. As an integral part of achieving social acceptability of open-pit mining, the stability of mining slopes must be carefully analyzed during the design process and the presence of public infrastructure near the slopes must be adequately considered. The province of Quebec does not have specific guidelines regarding such design considerations. This paper provides a short overview of the literature on some current practices regarding mining slope design close to public infrastructure. To demonstrate its applicability in the Quebec provincial context, the paper then investigates the stability of the west wall of the LAB Chrysotile open-pit mine in Thetford Mines (Quebec) near the new Road 112. Deterministic and probabilistic analyses were conducted using finite element shear strength reduction and limit equilibrium methods to investigate slope stability. The impact of pit infilling and rapid dewatering as well as long- term stability of the slope were investigated. The results of all analyses reveal that the current mining slopes at LAB Chrysotile are within acceptable design criteria limits. Key words: open-pit mining, slope stability, public infrastructure, deterministic and probabilistic analysis, case study. Resume : Au cours des dernieres annees, plusieurs grandes mines a ciel ouvert ont debute a etre exploitees dans la province de Quebec au Canada, et certains des plus grands puits prevus sont situes a proximite d'infrastructures publiques. Historiquement, les grandes mines a ciel ouvert etaient peu nombreuses dans plusieurs regions minieres, notamment l'Abitibi, ou les mines souterraines sont la norme. En tant que partie integrante de l'acceptation sociale d'une exploitation miniere a ciel ouvert, la stabilite des pentes doit etre soigneusement analysee au cours du processus de conception, et la presence d'infrastructures publiques pres des pentes doit etre dument examinee. La province de Quebec n'a pas de lignes directrices precises au sujet de ces considerations de conception. Cet article fournit un apercu de la litterature sur certaines pratiques actuelles concernant la conception des pentes de l'exploitation miniere pres d'une infrastructure publique. Afin de demontrer son applicabilite dans le contexte de la province de Quebec, l'article presente une analyse de la stabilite du mur ouest de la mine a ciel ouvert LAB Chrysotile, a Thetford Mines (Quebec), pres de la nouvelle route 112. Des analyses deterministes et probabilistes ont ete menees a l'aide des methodes de la reduction de la resistance au cisaillement par elements finis et de l'equilibre limite pour evaluer la stabilite des pentes. L'impact de l'assechement rapide et de remplissage de la fosse, ainsi qu'une stabilite a long terme de la pente ont egalement ete etudies. Les resultats de toutes les analyses revelent que les pentes de l'exploitation miniere actuelle de LAB Chrysotile sont acceptables dans les limites des criteres de conception. [Traduit par la Redaction] Mots-cles: l'exploitation miniere a ciel ouvert, stabilite de pente, infrastructures publiques, analyse deterministe et probabiliste, etude de cas., 1. Introduction Routine stability analysis of open-pit mine slopes involves a trade-off between stability and profit maximization. As the slope angle becomes steeper, the stripping ratio (waste to ore ratio) [...]

Rockfall simulations are often performed at various levels of detail depending on the required safety margins of rockfall-hazard-related assessments. As a pseudo benchmark, the simulation results from different models can be put side-by-side and compared with reconstructed rockfall trajectories, and mapped deposited block fragments from real events. This allows for assessing the objectivity, predictability, and sensitivity of the models. For this exercise, mapped data of past events from the Mel de la Niva site are used in this paper for a qualitative comparison with simulation results obtained from early calibration stages of the Flow-R 2.0.9, Rockyfor3D 5.2.15 and RAMMS::ROCKFALL 1.6.70 software. The large block fragments, reaching hundreds of megajoules during their fall, greatly exceed the rockfall energies of the empirical databases used for the development of most rockfall models. The comparison for this challenging site shows that the models could be improved and that combining the use of software programs with different behaviors could be a workaround in the interim. The findings also highlight the inconvenient importance of calibrating the simulations on a per-site basis from onsite observations. To complement this process, a back calculation tool is briefly described and provided. This work also emphasizes the need to better understand rockfall dynamics to help improve rebound models. [ABSTRACT FROM AUTHOR]

The earthquake that occured on 5 February 1663 is the first strong historical earthquake recorded in Canada and is currently estimated to have been located near La Malbaie and to have had a magnitude M of about 7. It left various signatures in the landscape that reveal its extent and significance. In the terrestrial domain, landslides were observed in various regions of Quebec, including Betsiamites, Saguenay, Charlevoix, and Mauricie. In the subaqueous domain, related mass movements were found along the St. Lawrence Estuary, the Saguenay Fjord, and various lakes on the Canadian Shield and likely also in the Appalachian. The minimum cumulative volume of mass movements associated with the 1663 earthquake is 1.7 [km.sup.3]. From the analysis of landslide-related data and using empirical methods for magnitude estimation, the position of the epicentre would be located in the Canadian Shield to the north of the St. Lawrence River with a minimum magnitude M of 7.2 ± 0.2 and a maximum magnitude that would be close to the maximum for the Charlevoix area, which has been previously estimated at M = 7.8 ± 0.6. Key words: seismicity, magnitude, intensity, landslides, underwater landslides, epicentre, location. Le seisme du 5 fevrier 1663 est le premier seisme historique violent au Canada dont la magnitude M est estimee comme etant autour de 7. Il a laisse dans le paysage plusieurs signatures qui en revelent l'etendue et l'intensite. Cote terrestre, on note des glissements de terrain dans diverses regions du Quebec dont la region de Betsiamites, du Saguenay, de Charlevoix et de la Mauricie. Cote subaquatique, plusieurs signatures de mouvements de terrain ont ete attribuees a ce seisme, particulierement le long de l'estuaire du Saint-Laurent, du fjord du Saguenay et quelques lacs localises sur le Bouclier laurentien et probablement dans les Appalaches. Le volume minimum cumule des glissements de terrain associes au seisme de 1663 est de 1,7 [km.sup.3]. A partir de l'analyse des donnees reliees aux mouvements de terrain causes par le seisme, et de l'utilisation de methodes empiriques pour l'estimation de la magnitude, la localisation de l'epicentre proposee du seisme serait situee sur le Bouclier canadien au nord du Saint-Laurent et le seisme aurait une magnitude M minimale de 7,2 ± 0,2 et une valeur maximale qui pourrait s'approcher de celle prevue pour la region de Charlevoix qui est de M = 7,8 ± 0,6. Mots-cles : seisme, magnitude, intensite, glissements de terrain, glissements sous-marins, epicentre, localisation., Introduction Le seisme du 5 fevrier 1663 est l'un des seismes historiques les plus forts ayant ete ressentis dans l'est de l'Amerique du Nord, avec une magnitude actuellement estimee a [...]

A marine environment presents various settings where talus slopes are formed via gravity-driven rockfall processes similar to those existing on land. This is the case along fjords or submarine canyons, where submarine installations or natural sanctuaries, such as coral reefs, need to be protected. In submarine rockfall analysis, the effect of the ambient fluid, in addition to hydrodynamic constraints and water currents, must be considered. A finite volume model has been developed to model two-dimensional rockfall behaviour in a Newtonian fluid, such as water or air. Turbulent and incompressible flow around the moving rock is described with a pressure-velocity iterative method on a dynamic three-dimensional unstructured mesh of polyhedral cells. Pressure, shear, and turbulent forces are then applied to the moving rock. In this paper, we compare underwater rockfall behaviour with air rockfall behaviour in three different situations: free fall, bouncing on a horizontal plane, and bouncing on an inclined plane. A true-scale experiment has been conducted to validate the model. The results of various modeling suggest that, contrary to the air case, the speed of the blocks will be strongly influenced by the block density and volume. Key words: rockfalls, submarine landslides, Navier-Stokes equations, numerical modeling. Tout comme le milieu aerien, le milieu marin peut presenter des environnements ou des talus rocheux sont formeis suite a des processus gravitaires impliquant des chutes de blocs. C'est le cas, par exemple, le long de fjords ou de canyons sous-marins. Un modele numerique a ete deiveloppei afin de modeliser le comportement en deux dimensions des chutes de blocs dans un liquide Newtonien. L'ecoulement incompressible et turbulent du fluide autour du bloc est r solu avec une methode iterative couplant la pression et la vitesse, sur un maillage dynamique non-structure; en trois dimensions compose de polyedres. Les forces dues a la pression, au cisaillement ainsi qu'a la turbulence sont calcukees autour du bloc et ensuite appliqueees a ce bloc afin de definir son mouvement. Dans cet article, le comportement des chutes de blocs dans l'eau sera compare a celui en milieu aerien dans trois situations diffeerentes : la chute libre, le rebond sur une surface horizontale ainsi que le rebond sur une surface inclineie. Un essai grandeur reel a ete realise afin de valider le modele deeveloppe. Les reesultats des diffeerentes modelisations suggerent que la vitesse des blocs sera fortement influenceee par sa masse volumique ainsi que par son volume. Mots-cles: chute de blocs, glissement de terrain sous-marin, equations de Navier-Stokes, modelisation numerique., Introduction The subaerial kinematics of falling rocks has been studied analytically and experimentally for several decades (Ritchie 1963; Pfeiffer and Bowen 1989; Azzoni et al. 1995). Almost all of these [...]

Introduction In their discussion about aerial laser scanning (ALS) and terrestrial laser scanning (TLS), Olsen and Stuedlein present some issues than we did not address in our paper (Jaboyedoff et [...]

Rheological properties of fine-grained sediments depending on index properties and salinity were examined. To characterize flow behaviors as a function of soil type, groups were made for convenience: (i) low-activity clays (group 1), (ii) high-activity clays (group 2), and (iii) silt-rich soils (especially for iron tailings; group 3). Low-activity and high-activity clays have characteristics of pseudoplastic (shear thinning) fluids, and exhibit a decrease in viscosity with increasing shear rate. However, in terms of the change in soil structure due to particle-particle interactions, illitic and montmorillonitic clays have opposite responses to salinity. As most of our data were obtained on low-activity clays--mostly illitic mixtures--we implemented a test program to ascertain the influence of montmorillonite on flow behavior. Using the Bingham model, a simple relationship is presented in terms of the possible critical limits of rheological transitions from clay- to silt- to sand-rich soils. Key words: low-activity clay, high-activity clay, iron tailings, shear thinning fluid, rheological properties, rheological transition. Les proprieetes rheeologiques des sediments fins dependantes des proprietes indices et de la salinite ont ete examinees. Des regroupements ont ete; faits afin de caracteiriser les comportements en ecoulement en fonction du type de sol : (i) argiles a faible activite (groupe 1), (ii) argiles a activite eleveee (groupe 2) et (iii) sols riches en silt (particulierement pour les residus de fer; groupe 3). Les argiles a faible et haute activite ont les caracteeristiques d'un fluide pseudo-plastique (fluidification par cisaillement), presentant une diminution de leur viscosite avec une augmentation du taux de cisaillement. Cependant, si l'on considere la variation de la structure du sol due aux interactions entre les particules, les argiles illitiques et montmorillonitiques ont une reaction opposeea la salinite. Puisque la majorite de nos donnees proviennent d'essais sur des argiles a faible activite;, principalement des melanges illitiques, nous avons effectuee des essais pour confirmer l'influence de la montmorillonite sur le comportement en eecoulement. A l'aide du modele de Bingham, une relation simple est preesenteee, qui deecrit les limites critiques possibles des transitions rheologiques d'argiles a silt a sable. Mots-cles: argile a faible activite, argile a activite; eleveee, reesidus de fer, fluidification par cisaillement, proprietees rheeologiques, transition rheologique. [Traduit par la Redaction], Introduction Subaqueous and subaerial mud or debris flows pose a great threat to life and infrastructure while being a major natural mechanism of sediment transport (Hampton et al. 1996; Jakob [...]

For more than 10 years, digital elevation models (DEM) produced by light detection and ranging (LIDAR) technology have provided new tools for geomorphologic studies and especially for landslide studies. In particular, terrestrial laser scanning (TLS) provides a great versatility of use. TLS can be used either for monitoring purposes or in an emergency situation that necessitates a rapid DEM acquisition for assessing a hazard. Using three examples we demonstrate the use fulness of TLS for landslide volume quantification, profile creation, and time series analysis. These case studies are landslides located in sensitive clays of eastern Canada (Quebec, Canada) or small rotational slides in river banks (Switzerland). Key words: aerial and terrestrial laser scanning, landslide, digital elevation models (DEM), sensitive clays, rotational slide. Depuis plus de 10 ans les modeles numeriques d'altitude (MNA) produits par technologie de << light detection and ranging >> (<< LIDAR >>) ont fourni de nouveaux outils tres utiles pour des etudes geomorphologiques, particulierement dans le cas des glissements de terrain. Le balayage laser terrestre (<< TLS >>) permet une utilisation tres souple. Le TLS peut etre employe pour la surveillance ou dans des situations d'urgence qui necessitent une acquisition rapide d'un MNA afin d'evaluer l'alea. Au travers de trois exemples, nous demontrons l'utilite du TLS pour la quantification de volumes de glissements de terrain, la creation de profils et l'analyse de series temporelles. Ces etudes de cas sont des glissements de terrain situes dans les argiles sensibles de l'est du Canada (Quebec, Canada) ou de petits glissements rotationnels dans les berges d'une riviere (Suisse). Mots-cles : balayage laser aerien et terrestre, glissement de terrain, modeles numeriques d'altitude (MNA), argiles sensibles, rotationel slide., Introduction Since the mid 1990s, light detection and ranging (LIDAR) techniques have been extensively used for topographic surveys in various regions. Data acquisition was first performed by airborne laser scanning [...]

The rate-dependent rheological behaviour of soils of different origins and characteristics was studied and the applicability of the power law model was examined. The studied soils were divided into three groups: (i) low-activity soils, (ii) high-activity soils, and (iii) silt-rich soils. The results show that the power law applies to all these soils and is representative of soil behaviour in a strain rate range corresponding to debris flows, which is generally not the case with the Bingham model. For low-activity clays, the power law index, n, is typically equal to 0.12 and seems to increase with the plasticity index; it is larger (i.e., in the range of 0.2-0.6) for silt-rich soils. Comparison of n values for tests performed on intact and remoulded low-activity clay specimens indicates that the power law index is possibly strain-rate dependent. Key words: rheological behaviour, strain-rate effect, power law index, low- and high-activity clays, silt-rich and coarser soils. Le comportement rheologique dependant des taux a ete etudie pour des sols ayant des origines et caracteristiques differentes, et l'applicabilite du modele de la loi de puissance a ete examinee. Les sols etudies etaient divises en trois groupes: (i) sols avec faible activite, (ii) sols avec activite elevee, et (iii) sols riches en silt. Les resultats montrent que la loi de puissance s'applique pour tous ces sols et est representative du comportement pour des taux de deformation correspondants a des ecoulements de debris, ce qui n'est generalement pas le cas avec le modele de Bingham. Pour les argiles a faible activite, l'indice n de la loi de puissance est typiquement egal a 0,12 et semble augmenter avec l'indice de plasticite; n est plus eleve, variant de 0,2 a 0,6, pour des sols riches en silt. Des comparaisons entre les valeurs de n obtenues d'essais effectues sur des echantillons intacts et remanies d'argile a faible activite indiquent que l'indice de la loi de puissance est possiblement dependant du taux de deformation. Mots-cles : comportement rheologique, effet du taux de deformation, indice de la loi de puissance, argiles a activite faible et elevee, sols grossiers riches en silt. [Traduit par la Redaction], Introduction The knowledge of the rheological behaviour of remoulded soils is of paramount importance for understanding and analyzing mud and debris flows. In particular, it allows the determination of the [...]

Resume : En 1996, suite a des pluies diluviennes, une couche de sediments propre s'est deposee dans la partie amont du fjord du Saguenay. Cette couche joue le role d'une [...]

Abstract: Fragmentation is one of the mechanisms involved in rock avalanches. Quantifying the associated energy during a rock avalanche can help to assess the influence of fragmentation on post-failure mass [...]