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The 1889 rock slide along Champlain Street is the one that caused the largest number of fatalities in this area of Québec 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 Baillairgé. 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 Baillairgé: the 1889 slide was a topple. This paper also highlights the significant contribution of Charles Baillairgé (1826–1906) in the understanding of rock slide processes along Cap Diamant. [ABSTRACT FROM AUTHOR]

A railroad crosses the coastal Gascons rockslide, in Quebec, Canada. This study improves the understanding of the rockslide's failure mechanism and post-failure behaviour responsible for the deformation in the railroad. The slide is an asymmetrical wedge failure of 410,000 m, in rocks made up of centimetre-scale beds of nodular calcilutite alternating with sandstones and limestone. The post-failure stage of the rockslide is characterised by continuous movement of blocks with speeds ranging from 6 to 110 mm/year. The main water table is just below the sliding surface, but precipitation and snowmelt can raise it above the sliding surface in the upper part of the slide. We propose a model for the rockslide, its failure mechanism, geometry and hydrogeology to provide a baseline for interpreting the near-real-time data collected since 2009. [ABSTRACT FROM AUTHOR]

Since 1964, the Iron Ore Company of Canada has deposited iron tailings resulting from mining operations into Wabush Lake, Western Labrador, Canada. This activity has resulted in a continuous hyperpycnal flow flowing over the lake floor. Bathymetric surveys were carried out between 1999 and 2008 as part of the overall environmental Iron Ore Company of Canada plans to maintain safe disposal strategies of tailings into the lake. Here, this dataset is used to study the evolution of different channels present in Wabush Lake and their link with knickpoints found at the head of most of these channels. The channels show notable evolution from one survey to the next. Some knickpoints and channels may be followed throughout more than one survey; the evolution of these knickpoints is the process responsible for the creation of erosional channels. The context in which they appear, as well as the evolution of some of the subaqueous channels is analysed. Cyclic steps and sediment waves are also found in the lake. These rhythmic bedforms, also created by the passage of turbidity currents, are analysed. Sediment waves found in Wabush Lake show values for both wavelength and wave height that are approximately one order of magnitude smaller than most of those found in the marine environment. [ABSTRACT FROM AUTHOR]

Time-dependent yield stress fluids display hysteresis with respect to reversible and irreversible structural changes. We report an experimental study of the rheological behavior of clay-rich soils (i.e., Mediterranean Sea and bentonite clays) and clay-poor material (i.e., iron mine tailings) that includes steady state, dynamic response, and hysteresis measurement. The Mediterranean Sea and bentonite clays are low- and high-activity clays, respectively. For the materials examined, different thixotropic behaviors are observed as a function of the time of shearing. These materials typically exhibit strong thixotropic behavior for a given shear rate in the limited time of shearing. In general, larger grain sizes produce larger hysteresis loop areas. However, the bentonite clay experiences an increase in viscosity with shear time, regardless of the salinity effect, for sufficiently long shearing times under continuous shear conditions at the shear rate of 1200 s − 1 (the maximum value in the present study). As a result, the flow behavior of clayey soils is strongly influenced by the imposed shearing time. [ABSTRACT FROM AUTHOR]

The monitoring of the 410 000 m 3 coastal Gascons rockslide, began in 2009. This paper presents and analyzes combined in-situ and satellite-based monitoring data to interpret the kinematic behavior of the slide and the evolution of the rockslide and the possible mechanisms that can lead to an accelerating phase of movement. The available data are (1) relative displacements, measured by thirteen crackmeters and manually with an extensometer tape; (2) absolute displacements, obtained from inclinometers and vertical shape accelerometer arrays in boreholes, total station surveys, and satellite-based point-target-analysis-InSAR (PTA); (3) the settlement of the railway ballast monitored by two horizontal shape accelerometer arrays; (4) groundwater pressures from nine vibrating wire piezometers; and (5) weather conditions. The study indicates that the role of water on displacements varies spatially within the rockslide. The rockslide's kinematic behavior enables us to develop evolution scenarios of the rockslide, which could be useful to conduct a risk analysis. This leads to the identification of critical zones for railroad safety. The unique set of monitoring data helps to elucidate the complexity of the rockslide's behavior. [ABSTRACT FROM AUTHOR]

This paper examines the geotechnical and rheological characteristics in terms of the transition from slide to flow in submarine landslides. This paper contains the results of a series of laboratory tests on the Saguenay Fjord fine-grained sediments. There are two types of tests: (1) vane shear tests in which intact and remolded samples are sheared and exposed to ambient water and (2) rheological tests performed on remolded sediment (with variable liquidity index) using a viscometer. The results explain the effect of water infiltration into soil. The sudden reduction in shear strength varied between about 300 and 800 Pa (Δw = 2–20%). The viscosity obtained from normalized flow curves (i.e., the logarithmic plot of shear stress versus the shear rate) were employed to characterize the rheology of soil. The mean value of viscosity (strength parameter in this case) as a function of shear rate from the results of fine-grained sediments varied between about 0.1 and 0.4. The values of yield stress and viscosity that were associated with the passage from the remolded to the fluidized state were in the range of 200 to 300 for Saguenay Fjord sediments. [ABSTRACT FROM PUBLISHER]

Fluidization processes in submarine landslides were studied by physical and numerical means. To examine soil-water interactions in the fluidization process, the computer axial tomography (CAT)-scan imaging techniques and laboratory vanes were utilized with a focus on the transition from failure to post-failure. Based on the results that were obtained from the scanning images and laboratory vane tests after the process of water infiltration into the soil sample, it appears that a gradual decrease in shear strength is unavoidable with increasing water content in a shear zone. From the numerical results, which were based on the dam-break problem using the transport equation coupled with the Navier-Stokes equation, if the slide is assumed to be initially unstable, a possible transition of fluidization processes that are dependent upon a change in density occurs. The density of the mud decreases with time during the flow at the interface between mud and water. The upper part of the mud pushes the lower part of the mud and then induces a rotation of mud that moves substantial distances. These results emphasize the importance of the soil-water interaction, the need for sediment rheology and the influence of the water circulation on the motion of the landslide. [ABSTRACT FROM PUBLISHER]

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 km3. 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. [ABSTRACT FROM AUTHOR]

Abstract: At least three major landslide events formed the submarine and subaerial Betsiamites (Québec, Canada) landslide complex and mobilized an estimated total volume of 2000million m3 (2km3). Linkage between offshore and onshore geophysical investigations with borehole data and in situ testing allows reconstruction of the architecture of the Betsiamites River delta area and leads to the identification of the main failure events. The submarine scar of the Betsiamites landslide complex may have resulted from a first failure, dated at about 9250cal BP, which mobilized a minimum volume of 200million m3. A second landslide dated at 7250cal BP mobilized a volume of 1300million m3 over an area of 54km2. The Betsiamites submarine landslide event dated at 7250cal BP left the largest scar yet identified on the St. Lawrence estuary seafloor. Furthermore, this paper demonstrates that the subaerial scar of the Betsiamites landslide complex is a result of the Colombier landslide event, which was initiated by the 1663 earthquake and involved four successive failure phases: one submarine and three subaerial. The February 5th 1663 earthquake triggered a submarine landslide event, which reached the shoreline, and led in a short period of time successively to two subaerial flowslides in sensitive clayey material and a subaerial lateral spread. The four failure phases mobilized a possible total volume of about 530million m3 over an area of 20km2. The Colombier landslide event is among the largest documented historic landslides in Canada. The presence of submarine scars left by the early Holocene events acted as predisposition factors for the development of the failure while the earthquake of 1663 was the main triggering factor of the first submarine failure. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Over the last 100,000 years, the U.S. Atlantic continental margin has experienced various types of mass movements some of which are believed to have taken place at times of low sea level. At one of these times of low sea level a significant trigger caused a major submarine mass movement off the coast of Virginia: the Currituck slide which is believed to have taken place between 24 and 50 ka ago. This slide removed a total volume of about 165 km3 from this section of the continental slope. The departure zone still shows a very clean surface that dips at 4° and is only covered by a thin veneer of postglacial sediment. Multibeam bathymetric and seismic survey data suggest that this slide took place along three failures surfaces. The morphology of the source area suggests that the sediments were already at least normally consolidated at the time of failure. The slide debris covers an area as much as 55 km wide that extends 180 km from the estimated toe of the original slope. The back analysis of slide initiation indicates that very high pore pressure, a strong earthquake, or both had to be generated to trigger slides on such a low failure plane angle. The shape of the failure plane, the fact that the surface is almost clear of any debris, and the mobility analysis, all support the argument that the slides took place nearly simultaneously. Potential causes for the generation of high pore pressures could be seepage forces from coastal aquifers, delta construction and related pore pressure generation due to the local sediment loading, gas hydrates, and earthquakes. This slide, and its origin, is a spectacular example of the potential threat that submarine mass movements can pose to the US Atlantic coast and underline the need to further assess the potential for the generation of such large slides, like the Grand Banks 1927 landslide of similar volume. [Copyright &y& Elsevier]

Abstract: A complex submarine geomorphology was revealed from multibeam bathymetry and seismic reflection surveys conducted between 2001 and 2007 in the Lower St. Lawrence Estuary offshore Betsiamites River, Quebec, Canada. In this paper, we describe the submarine morpho-sedimentology of an area of ∼500 km2 with focus on the consequences of four mass movement events. The general morpho-sedimentology of the area and submarine features resulting from mass movement processes, channel erosion and gas seepage are described. A spatio-temporal sequence for the occurrence of the mass movements and a chronology for the failures are established. We propose dates for four of the observed mass movement deposits. A buried paraglacial debris flow deposit is dated as older than 9280 cal BP, whereas a major landslide scar characterized by two topographic depressions on the shelf and a sediment lobe in the Laurentian Channel were dated around 7250 cal BP. Morphological observations and sediment core analyses allow us to identify a least two different recent (i.e., less than 500 yr old) debris flow accumulations associated with two recent earthquakes: (1) the AD 1663 (M∼7) and (2) AD 1860 (M∼6) or AD 1870 (M∼6.5) earthquakes. In addition to a complex geomorphology influenced by mass movements, we have identified several regions on the shelf and on the Laurentian Channel with evidence of pockmarks, which could potentially influence submarine slope stability in the Estuary. [Copyright &y& Elsevier]

In 1996, following torrential rains, a layer of clean sediments was deposited in the upstream part of the Saguenay Fjord. This layer acted as a damping layer between contaminated sediments and the Saguenay waters. It is important to collect information on the water–sediments interface, which is the site of exchanges between the sediments and the waters. Three oceanographical campaigns have allowed us to obtain the data on the velocity of the benthic currents and the properties of the surface sediments. The velocities have been obtained by means of two current meters located at 3 m from the bottom and by means of registered videos. These two types of measurements have given comparable results. The main information collected on the sediments were their water content, grain size, density, and the presence of benthic fauna. The distribution of the main biogenic structure, the tubes of polychetes, is related to the depth of the site and to the grain size of the sediments. For the surface layer, large variations of the water content were obtained during the field measurements. Tests with an axial tomodensitometer have revealed a large variation in the density of the sediments in the top 2.5 cm. [ABSTRACT FROM AUTHOR]

Using some new and previously published sedimentation rate data the relationship between sedimentation rate and distance from sediment source was statistically modelled for the Saguenay Fjord, Canada. Sedimentation rates obtained from these models can be used to reasonably predict the range of ages for submarine mass movements in the Saguenay Fjord. Error in the prediction is mostly associated with the natural variability of sedimentation rate. Ranges of dates were predicted for several submarine mass movements in the Upper Saguenay Fjord. In many cases the predicted date range did not correspond to the 1663 earthquake which had been previously assumed to have triggered these mass movements. [ABSTRACT FROM AUTHOR]

Abstract: A flash flood that occurred in July 1996 in the Saguenay area (Québec, Canada), deposited a bed of cohesive sediments, average of 10–60 cm thick, over an area of 65 km2 of the deep fjord basin of the upper Saguenay Fjord. Because this turbidite covered contaminated sediments, the resuspension potential of surficial sediments is an important parameter in determining the efficiency of the 1996 layer as a natural capping layer. This is because contaminants that may have diffused through the 1996 layer may be resuspended. The resuspension potential of surficial sediments in Saguenay Fjord was investigated in situ over a 3-yr period at fifteen sites in the Baie des Ha! Ha! and the North Arm using a benthic flume, the Miniflume. In addition, geotechnical measurements, photographs of benthic sediments and recordings of benthic current velocities were also carried out. The measured critical velocities of sediment resuspension (u c) vary between 7 and 15 cm s−1. The maximum bottom current speed recorded in the North Arm and in Baie des Ha! Ha! from May to August 2000 was 27 cm s−1. Erosion depths were determined from Miniflume data combined with laboratory measurements carried out with an axial tomography scanner, which provided variation of sediment density at an interval of 0.13 mm. A general relationship between depth of erosion (ze, mm) and shear stress applied on the bed (τ b, Pa) was determined. As Saguenay Fjord sediment characteristics vary greatly from one station to another, the potential for resuspension of surficial sediments shows the same trend. [Copyright &y& Elsevier]

Abstract: As a contribution to the understanding of the mechanisms and causes for Storegga Slide, the mineralogy and microstructure of samples from a series of boreholes from the slide neighbourhood have been analysed. The results show a change from kaolinite-rich oozes through smectite-rich fossilferous clays/clayey oozes to illite dominated hemipelagic and glacial sediments from the Brygge (Eocene to earliest Miocene) to Kai (earliest Miocene to late Pliocene) to Naust Formations (late Pliocene to present), respectively. The deposits are interpreted as the effect of denudation of weathered regolith and an increase in physical erosion in conjunction with the deterioration of the climate and the initiation of glacial cycles during the late Cenozoic. During the Quaternary, climate has controlled the mixing of current transported, fine grained sediments that are probably derived from the region around the Faeroe Islands and coarser grained glacial sediments containing a broad spectrum of minerals eroded from the North Sea and Scandinavian mainland. Since currents have been most important during warm periods, sediments from these periods are finer grained and contain more smectite than the glacial sediments. However, it is concluded that the mineralogical differences between finer grained sediments from warm periods and the coarser grained glacial sediments are not great enough to explain the ubiquitous utilisation of glacial marine/hemipelagic sediments as slip planes for the slides in the area, but that this is probably a consequence of the differences in the grain size distribution of the sediments. Voids that may be casts left behind by gas hydrates have been observed. [Copyright &y& Elsevier]

Analysis of morphology, failure and post-failure stages of the Palos Verdes debris avalanche reveals that it may have triggered a significant tsunami wave. Our analysis of the failure itself indicates that the slope is stable under aseismic conditions but that a major earthquake (with a magnitude around 7) could have triggered the slide. A post-failure analysis, considering the debris avalanche as a bi-linear flow, shows that peak velocities of up to 45 m/s could have been reached and that the initial movement involved a mass of rock less than 10 km wide, 1 km long and about 50–80 m thick. Initial wave height estimates vary from 10 to 50 m. Tsunami waves propagating to the local shoreline would be significantly smaller. Such a range demonstrates our lack of proper knowledge of the transition from failure to post-failure behavior related to mass movements. Further investigations and analyses of terrestrial and submarine evidence are required for a proper hazard assessment related to tsunami generation in the Los Angeles area. [Copyright &y& Elsevier]

In 1996 a major flood occurred in the Saguenay region, Quebec, Canada, delivering several km3 of sediment to the Saguenay Fjord. Such sediments covered large areas of the, until then, largely contaminated fjord bottom, thus providing a natural capping layer. Recent swath bathymetry data have also shown that sediment landslides are widely present in the upper section of the Saguenay Fjord, and therefore, should a new event occur, it would probably expose the old contaminated sediments. Landslides in the Upper Saguenay Fjord are most probably due to earthquakes given its proximity to the Charlevoix seismic region and to that of the 1988 Saguenay earthquake. In consequence, this study tries to characterize the permanent ground deformations induced by different earthquake scenarios from which shallow sediment landslides could be triggered. The study follows a Newmark analysis in which, firstly, the seismic slope performance is assessed, secondly, the seismic hazard analyzed, and finally an evaluation of the seismic landslide hazard is made. The study is based on slope gradients obtained from EM1000 multibeam bathymetry data as well as water content and undrained shear strength measurements made in box and gravity cores. Ground motions integrating local site conditions were simulated using synthetic time histories. The study assumes the region of the 1988 Saguenay earthquake as the most likely source area for earthquakes capable of inducing large ground motions in the Upper Saguenay region. Accordingly, we have analyzed several shaking intensities to deduce that generalized sediment displacements will begin to occur when moment magnitudes exceed 6. Major displacements, failure, and subsequent landslides could occur only from earthquake moment magnitudes exceeding 6.75. [Copyright &y& Elsevier]

In July 1996 a major rainstorm and flood took place in the Saguenay Fjord. Backscatter strength measurements made with a Simrad EM1000 multibeam echosounder in 1993, 1997 and 1999 have shown spatial and temporal variations, which are interpreted in relation to the occurrence of the flood. After empirical calibration of the different maps the data show an overall diminution of 5 dB in backscatter strength in 1997, 1 yr after the flood took place, while the data sets obtained in 1993 and 1999 show comparable levels of backscatter strength. The different data sets show a similar pattern of low and high backscatter patches, which represent variations of the backscatter strength of a few decibels. Several grain size and water content measurements were also carried out on sediment box core and grab samples from the Fjord bottom in 1997 and 1999. These have shown that the areas with higher acoustic backscatter correspond to the finer sediments, while the low backscatter patches correspond to the coarser material. The data show little relation between water content and backscatter strength, thus indicating a poor dependence between the impedance terms (bulk density and sound speed) and the backscatter. Having taken this into account, the major contribution to backscatter strength is assumed to result from differences in surface and volume roughness of the sediment. Since finer grain sizes offer higher backscatter the grain size of the sediment is not considered as being a major contributor to roughness and hence, backscatter strength. The major factor that seems to control roughness generation in the Saguenay Fjord is considered to be bioturbation. The areas where geological processes most physically disturb the bottom, which coincide with the areas where also most accumulation takes place and the coarser grain sizes are deposited, are more sparsely colonized by organisms. This results in a lower degree of bioturbation, lower roughness and thus, backscatter strength. This hypothesis helps explain the variation in backscatter strength observed between the different measurement years. The several million tons of sediment deposited in the Fjord bottom after the 1996 flood buried the benthic fauna, which was still recovering 1 yr later. The less bioturbated sediment at this time would present lower roughness with respect to the 1993 and 1999 data resulting in a lower backscatter strength. [Copyright &y& Elsevier]

As part of the STRATAFORM project, a series of cores were obtained from the Eel River Margin area of Eureka, California. The geotechnical analysis of intact specimens and of reconstituted samples provides some insight on the development of shear strength with burial. The results show the effect of bioturbation in the early part of the lifetime of a sediment. SEDCON tests were used to proposed various relationships which help predict the changes in density, liquidity index, and strength as a function of depth. These relationships are found useful from near the water sediment-interface down to a depth of at least 400 m in the sediment column. [ABSTRACT FROM AUTHOR]

Due to the recent development of well-integrated surveying techniques of the sea floor, significant improvements were achieved in mapping and describing the morphology and architecture of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as that found on land. Submarine mass movements, however, can have run-out distances in excess of 100 km, so their impact on any offshore activity needs to be integrated over a wide area. This great mobility of submarine mass movements is still not very well understood, particularly for cases like the far-reaching debris flows mapped on the Mississippi Fan and the large submarine rock avalanches found around many volcanic islands. A major challenge ahead is the integration of mass movement mechanics in an appropriate evaluation of the hazard so that proper risk assessment methodologies can be developed and implemented for various human activities offshore, including the development of natural resources and the establishment of reliable communication corridors.Key words: submarine slides, hazards, risk assessment, morphology, mobility, tsunami.Le développement récent de techniques de levés hydrograhiques pour les fonds marins nous a permis d'atteindre une qualité inégalée dans la cartographie et la description des glissements sous marins. À l'exception des courants de turbidité, on retrouve dans le domaine aquatique les mêmes types de mouvements de terrain que sur terre. Par contre, les glissements sous-marins peuvent atteindre des distances excédant 100 km de telle sorte que leur impact sur les activités offshore doit être pris en compte sur de grandes étendues. La grande mobilité des glissements sous-marins n'est pas encore bien comprise, comme pour le cas des coulées de débris cartographiées sur le cône du Mississippi ainsi que pour les grandes avalanches rocheuses sous-marines retrouvées au pourtour des îles volcaniques. Un défi majeur auquel nous faisons face est celui de déterminer les aléas associés aux divers types de mouvements sous-marins ainsi que les risques associés à l'activité humaine, telle que l'exploitation des ressources naturelles et l'établissement de routes de communications fiables.Mots clés : glissements sous-marins, morphologie, aléa, risque, mobilité, tsunami. [ABSTRACT FROM AUTHOR]

A soil investigation was carried out at two sites in Singapore and Bangkok, Southeast Asia, and the results were compared with those from a site in Ariake, Japan. Soil samples at all the sites were retrieved using the Japanese sampling method to nullify the effect of sampling on sample quality. From the laboratory tests, consolidation characteristics and undrained shear strength were measured. In addition to the mechanical tests, X-ray diffraction and scanning electron microscope tests were carried out to identify clay minerals and to study their microstructure. Great differences in physical and mechanical properties of these clays were observed, which may be attributed to the difference in their clay mineral components and variation in the sedimentation environment.Key words: site investigation, marine clay, undrained shear strength, anisotropy, consolidation, clay mineral.Les études de sols ont été réalisées à deux sites en Asie du sud-est : Singapour et Bangkok. Les résultats des essais obtenus de ces études ont été comparés à ceux obtenus au site de Ariake, Japon. Dans cette étude, tous les échantillons analysés ont été recueillis à l'aide de techniques d'échantillonnage japonaises afin d'éviter l'effet de la méthode d'échantillonnage sur la qualité des résultats. Les propriétés caractéristiques de consolidation et de résistance au cisaillement ont ainsi pu être déterminés par des essais en laboratoire. En plus des essais mécaniques, des analyses par diffraction-X et des observations en microscopie à balayage ont permis d'identifier les minéraux argileux présents de même que les caractéristiques microstructurales. Des différences importantes ont été observées dans les propriétés physique et mécanique lesquelles peuvent être attribuées à leur différence tant au niveau de la minéralogie des argiles que des environnements sédimentaires.Mots clés : étude de site, argiles marines, résistance au cisaillement non-drainée, anisotropie, consolidation, minéralogie des argiles. [ABSTRACT FROM AUTHOR]

To locally evaluate the rockfall hazard for some buildings of the municipality of Bex, Switzerland, a 30 m high by 110 m long gypsum cliff was inspected between March 2017 and 2018. Comparative rockfall simulations were then performed from five observed potential instabilities using four different rockfall simulation programs/models to estimate the probability for the buildings to be reached by rockfalls. A present catchment ditch was considered in the simulations, and to extend it, some catchment designs (fences and ditches) were also tested. The visual inspections were accompanied by temporal acquisitions of 3D point cloud terrain models (DTM) with terrestrial laser scanner (TLS), mobile TLS and photogrammetry. During this period, 15 small rockfalls were observed by comparing the DTMs and confirmed visually on pictures. Their mean volume evaluated with the DTMs is around 0.012 m3 with a standard deviation (std.) of 0.016 m3. The largest of these observed rockfalls was a thin block with a width of 1.2 m and a height of 0.5 m, for a volume of 0.058 m3. The main joint-sets of the rock face were measured on the point clouds. Five potential instabilities were identified based on the observation of surrounding open cracks for three of them, and 3 to 8 m persistent open cracks for the two others. Their mean volume is around 11 m3 with a std. of 11 m3 and a maximum volume of around 25 m3. The potential propagation was then evaluated and compared using: RocFall simulation program from RocScience that works on detailed 2D slope profiles with their 1) lumped mass and 2) rigid body models; 3) Rockyfor3D from ecorisQ that works on 2.5D gridded terrain models with 2x2 m pixels at best resolution; and 4) our 3D rockfall simulation program in development that works on highly detailed 3D point cloud DTMs or gridded terrain models. The reach distances and energy lines obtained with our program in development and RocFall are very similar. They reach the buildings in average from 0.4 to 6.3 % of the simulated trajectories. Those with Rockyfor3D goes further, with more lateral spreading and reach buildings in average for 69 % of the simulated trajectories. The existing catchment ditch, where present, seems efficient based on most simulations from three of the four programs/models used. In contrast, those from Rockyfor3D show that this catchment has almost no effect on the propagation and reach distances. Similar behaviours were obtained with the extension catchment ditch design. The same goes with the extension catchment fence designs, but this time with reduced propagation in some Rockyfor3D's simulations. The results of similar case studies combining Rockyfor3D and protective measures should be interpreted with caution.In summary, this study shows that at local scale, rockfall simulations seems to be greatly influenced by the quality/resolution of the terrain model, especially for runout distance and 3D effects. Thereby, the results of such rockfall simulations must be interpreted with caution because the local hazard value might greatly variate compared to the one from regional hazard mapping. [ABSTRACT FROM AUTHOR]

Sensitive clays, mostly found in Eastern Canada and Scandinavia, are prone to various types of landslides; among them are flowslides that may affect hectares of land. Debris from those slides has high mobility, with runout distances that may extend over hundreds of meters in relatively flat and non-channelized terrain. Most studies on the mobility use apparent rheological properties to back-calculate the runout behavior of these landslides. This works well for back-analyses of landslides but is of little help in a context of hazard mapping, where prospective analysis of future landslides is necessary. In this study, a new factor, using the destructuration index concept, is introduced to estimate the remaining energy available as kinetic energy for runout after the remolding of the sensitive clay: the energy reduction factor (FER). Using the FER allows the use of real rheological data acquired with a rheometer to analyze the post-failure behavior of a flowslide in sensitive clays. This method is applied on a sensitive clay landslide which took place in Quebec and where rheological and geotechnical data are available. [ABSTRACT FROM AUTHOR]

Process-based rockfall simulation models attempt to better emulate rockfall dynamics to different degrees. As no model is perfect, their development is often accompanied and validated by the valuable collection of rockfall databases covering a range of site geometries, rock masses, velocities, and related energies that the models are designed for. Additionally, such rockfall data can serve as a base for assessing the model's sensitivity to different parameters, evaluating their predictability and helping calibrate the model's parameters from back calculation and analyses. As the involved rock volumes/masses increase, the complexity of conducting field-test experiments to build up rockfall databases increases to a point where such experiments become impracticable. To the author's knowledge, none have reconstructed rockfall data in 3D from real events involving block fragments of approximately 500 metric tons. A back analysis of the 2015 Mel de la Niva rockfall event is performed in this paper, contributing to a novel documentation in terms of kinetic energy values, bounce heights, velocities, and 3D lateral deviations of these rare events involving block fragments of approximately 200 m3. Rockfall simulations are then performed on a "per-impact" basis to illustrate how the reconstructed data from the site can be used to validate results from simulation models. [ABSTRACT FROM AUTHOR]

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 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 × 107 m3 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wabush Lake is one of the few very well-constrained source-to-sink sedimentary systems in the world that exhibits near-continuous turbidity currents. In this system, approximately 20 million tons of mine tailings are delivered each year to a 40 km 2 lake. Multibeam bathymetric surveys of this lake were carried out between 1999 and 2011. In addition, a program of extensive sampling and seismic surveys, an airborne LiDAR survey and a photogrammetric survey were carried out during this period. The objective of this study was to determine the evolution through time of this anthropic source-to-sink system, from the point where sediments exit the slurry pipelines at the head of the system to the distal end and bottom of the Lake. The total volume of the Lake is around 1 × 10 9 m 3 . Analysis of subaerial and subaqueous datasets allows the evaluation of disposal strategies on the delta topset and on tailings accumulation. Disposal strategies influence the dynamics of the channels on the topset, thus in turn affecting the accumulation of tailings throughout the lake, as well as the shoreline advancement rate. Subaqueous erosional channels present on the bed of the Lake influence the depositional pattern of tailings as well as their granulometric distribution. These erosional channels are created by the shoreward migration of knickpoints. In some places, this migration can be documented over multiple surveys. Finally, sequential analysis of the 1999, 2004, 2006, 2008 and 2011 surveys has allowed detailed documentation of the infilling of the Lake, including the migration of sediment depocenters, the mechanism of emplacement and the progressive infilling of a series of minibasins. [ABSTRACT FROM AUTHOR]

Wabush Lake is one of the few very well-constrained source-to-sink sedimentary systems in the world that exhibits near-continuous turbidity currents. In this system, approximately 20 million tons of mine tailings are delivered each year to a 40 km 2 lake. Multibeam bathymetric surveys of this lake were carried out between 1999 and 2011. In addition, a program of extensive sampling and seismic surveys, an airborne LiDAR survey and a photogrammetric survey were carried out during this period. The objective of this study was to determine the evolution through time of this anthropic source-to-sink system, from the point where sediments exit the slurry pipelines at the head of the system to the distal end and bottom of the Lake. The total volume of the Lake is around 1 × 10 9 m 3 . Analysis of subaerial and subaqueous datasets allows the evaluation of disposal strategies on the delta topset and on tailings accumulation. Disposal strategies influence the dynamics of the channels on the topset, thus in turn affecting the accumulation of tailings throughout the lake, as well as the shoreline advancement rate. Subaqueous erosional channels present on the bed of the Lake influence the depositional pattern of tailings as well as their granulometric distribution. These erosional channels are created by the shoreward migration of knickpoints. In some places, this migration can be documented over multiple surveys. Finally, sequential analysis of the 1999, 2004, 2006, 2008 and 2011 surveys has allowed detailed documentation of the infilling of the Lake, including the migration of sediment depocenters, the mechanism of emplacement and the progressive infilling of a series of minibasins. [ABSTRACT FROM AUTHOR]

We report on a 4.1 (±0.2) km diameter and 185 m deep circular submarine structure exposed on the seabed in >40 m water depths in the northwestern Gulf of St. Lawrence (Eastern Canada) from the analysis of high-resolution multibeam bathymetric and seismic data. The presence of a circular form characterized by a central uplift and concentric rings resembles the morphology and geometry of complex meteorite impact structures. Also, other origins, such as kimberlites, intrusions, karsts, or diapirs, can be eliminated on geological criteria. A single 4 cm long breccia fragment recovered from the central uplift has numerous glassy droplets of fluorapatite composition, assumed to be impact melts, and a single quartz grain with planar intersection features thought to be shock-induced planar deformation features ( PDFs). The absolute age of this possible impact structure is unknown, but its geological setting indicates that it was formed long after the Mid-Ordovician and before regional pre-Quaternary sea-level lowstands. Present results outline the need for further examination to confirm an impact origin and to precisely date the formation of the structure. [ABSTRACT FROM AUTHOR]

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-Pérade, 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. [ABSTRACT FROM AUTHOR]

Abstract: The Champlain Sea clays of Eastern Canada are incised by numerous rivers. Their slopes have been modified by landslides: on the Chacoura River near Trois-Rivières (Quebec), several large landslide scars, more or less recent, are visible. The role of erosion (channel incision, lateral channel migration and erosion of slopes due to agricultural drainage) as a trigger of these landslides is important. The aim of this study is to understand how erosion and landslides are related to valley development. From a detailed analysis of aerial photographs and DEMs, a map of the phenomena has been drawn by identifying various elements such as landslides, limits of the slope, position of the channel, and the area covered by forest. It is shown that channel change and erosion are strongly linked to landslides by the fact that they change the bank morphology in an unstable way. A slide in itself is a natural way for the slope to achieve stability. But when it occurs in a stream, it creates a disturbance to the stream flow enhancing local erosion which may change the river path and generate more erosion downstream or upstream resulting in more slides. Cross-valley sections and a longitudinal profile show that landslides are a major factor of valley formation. It appears that the upper part of the Chacoura River valley is still unaffected by landslides and has V-shaped sections. The lower part has been subject to intense erosion and many landslide scars can be seen. This shows that the valley morphology is transient, and that future activity is more likely to occur in the upper part of the river. Therefore the identification of areas prone to erosion will help determine the possible location of future large landslides just like the ones that occurred in the lower part. [Copyright &y& Elsevier]

A fan delta developed under the constraints of a moving point of flow-sediment supply is described. The sediment mixtures used in the experiments were chosen to approximate field conditions, with the coarser fractions depositing to form the topset (subaerial delta surface) and foreset, and the finer fractions forming a turbidity current that plunges near the shoreline, overrides the foreset, and continues into deeper water to emplace a bottomset. The migration rate of the feed point was adjusted so that the base of the lateral foreset along one side just touched the flume wall, so leaving open water on that side. The experiments provide insight into the sedimentation processes associated with these three co-evolving structures of the delta, i.e. its topset, foreset, and bottomset. The results indicate that the lateral delta extent can be controlled via the downstream migration of its sediment source. [ABSTRACT FROM AUTHOR]

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 usefulness 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). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Presents a study which developed a numerical model called TRANSCAP-1D to stimulate the migration of dissolved contaminants through sediment cap in a marine environment. Mathematical formulation and numerical solutions used; Application of the model to the flood sediments of the Saguenay Fjord; Effect of variable input parameters on the response of the model.

It is well known that organic matter may affect the cementing process in soils, but what happens when cement is added to an organic soil? Both the organic matter content and the nature of this organic matter affect the properties of a treated soil. It appears that some organic compounds delay or even inhibit the hydration process of cement, while others do not affect the reaction at all. This paper presents some results of a laboratory study in which 13 different organic compounds were added separately to two different soils, and then treated with 10% cement. To assess the cementing process, undrained shear strength was measured on the different specimens, and some chemical analyses were performed on the pore liquid. The results indicate that the organic acids producing a pH lower than 9 in the pore solution strongly affect the development of cementing products and almost no strength gain was noted. Also, oils and hydrocarbons, which are insoluble in water, delay the cement hydration but do not affect the final strength. Finally, the pH value and the SO[sub 4] concentration in the pore solution are good indicators of the cementing effectiveness of the treated specimens.Key words: soil stabilization, organic compounds, undrained shear strength, cement, chemical analyses.Il est bien connu que la matière organique peut affecter le processus de cimentation dans les sols, mais qu'arrive-t-il lorsque le ciment est ajouté à un sol organique? Tant la matière organique que sa nature affecte les propriétés du sol traité. Il semble que certains composés organiques retardent ou même empêchent le processus d'hydratation du ciment, alors que d'autres n'affectent aucunement la réaction. Cet article présente des résultats d'une étude en laboratoire dans laquelle 13 composés organiques différents ont été ajoutés séparément à deux différents sols, et ensuite traités avec 10 % de ciment. Pour évaluer le processus de cimentation, la résistance au cisaillement non drainé a été mesurée sur différents spécimens, et des analyses chimiques ont également été réalisées sur le liquide interstitiel. Les résultats indiquent que les acides organiques qui produisent un pH inférieur à 9 dans la solution interstitielle affectent fortement le développement des produits de cimentation de sorte qu'on note presque aucun gain de résistance. Aussi, les huiles et les hydrocarbures insolubles dans l'eau retardent l'hydratation du ciment, mais n'affectent pas la résistance finale. Finalement, la valeur du pH et la concentration de SO[sub 4] dans la solution interstitielle sont de bons indicateurs de l'efficacité du traitement au ciment des spécimens.Mots clés : stabilisation du sol, composés organiques, résistance au cisaillement non drainé, ciment, analyses chimiques.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Proposes a one-dimensional numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows. Model formulation; Discussion on the Lagrangian form of governing equations; Factors influencing the runout characteristics of debris flow; Conclusions.

The method of soil stabilization is well known and has been used throughout the world for many decades to improve some soil properties. Although many researchers have studied the effect of adding a cementing agent to a soil, not many of these researchers have explored the effect of treatment on the resulting properties of high water content soils like dredged material. Also, there has been little work concerning the prediction of the mechanical changes to the soil. Therefore, this paper summarizes the results of a research project conducted to define the general mechanical behavior of high water content clayey soils from eastern Canada treated with lime or cement, in terms of compressibility. In the light of this research, the general compressibility behavior has been obtained, defined by relationships between initial void ratio, additive content, and vertical yield stress for a given inorganic or organic soil. These relationships have been normalized on the basis of the one-dimensional compression curve of the remolded and reconstituted untreated soil to give a simple method for predicting the vertical yield stress of a treated soil for any initial void ratio and its resistance to compression.Key words: stabilization, compressibility, yield stress, clayey soils, lime, cement.La méthode de stabilisation des sols est bien connue et a été utilisée depuis plusieurs décades à travers le monde pour améliorer certaines propriétés des sols. Quoique plusieurs chercheurs aient étudié l'effet de l'addition d'un agent de cimentation au sol, peu d'entre eux ont exploré l'effet du traitement sur les propriétés résultantes des sols à teneur en eau élevée tels que les matériaux dragués. Également, il y a eu peu d'études portant sur la prédiction des changements mécaniques apportés au sol. En conséquence, cet article résume les résultats d'un projet de recherche réalisé pour définir un comportement mécanique général en terme de compressibilité de sols argileux à hautes teneurs en eau de l'est du Canada avec de la chaux ou du ciment. À la lumière de cette recherche, on a obtenu le comportement général en compressibilité défini par la relation entre l'indice des vides initial, la teneur en additif, et la contrainte de préconsolidation apparente verticale pour un sol donné organique ou inorganique. Finalement, ces relations ont été normalisées sur la base de la courbe de compression unidimensionnelle du sol non traité remanié et reconstitué pour donner un méthode simple pour prédire la contrainte de préconsolidation apparente verticale d'un sol traité pour n'importe quel indice de vide initial, et sa résistance à la compression.Mots clés : stabilisation, compressibilité, contrainte de préconsolidation apparente, sols argileux, chaux, ciment.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A major mining slope failure occurred in July 2012 on the East wall of the LAB Chrysotile mine in Canada. The major consequence of this failure was the loss of the local highway (Road 112), the main economic link between the region and the Northeast USA. This paper is part of a proposed integrated remote sensing-numerical modelling methodology to analyze mining rock slope stability. This paper presents the Light Detection and Ranging (LiDAR) monitoring of this slope failure. The main focus is the investigation of that rock slide using both terrestrial (TLS) and airborne (ALS) LiDAR scanning. Since 2010, four ALS and 14 TLS were performed to characterize and monitor the slide. First, laser scanning was used to investigate the geometry of the slide. The failure zone was 1100 m by 250 m in size with a mobilized volume of 25 hm. Laser scanning was then used to investigate the rock slide's 3D displacement, thereby enabling a better understanding of the sliding kinematics. The results clearly demonstrate the ability of the proposed approach to monitor and quantify large-scale rock mass failure. The slope was monitored for a period of 5 years, and the total displacement was measured at every survey. The maximum cumulative total displacement reached was 145 m. This paper clearly shows the ability of LiDAR scanning to provide valuable quantitative information on large rock mass failures involving very large displacements. [ABSTRACT FROM AUTHOR]

Disturbed lacustrine deposits of eastern Canada have been associated with past seismic events in the intraplate Western Québec Seismic Zone (WQZ) and the Charlevoix–Kamouraska Seismic Zone (CKSZ). With five major earthquakes that occurred during historical times and hundreds of minor earthquakes, the CKSZ is the most active seismic zone in eastern Canada. Here we present new high-resolution multibeam bathymetric, subbottom profiler and sediment core data collected in Lake Témiscouata, southeastern Québec, the largest lake located within the influence of the CKSZ. The occurrence of mass-movements in the highly cohesive glaciolacustrine deposits of the lake produced a peculiar lacustrine landscape consisting of steep slide scars and residual mounds and very narrow residual crests. Our data indicate that postglacial times were marked by recurrent seismically-induced mass-movement events that cannot be individually identified in the sedimentary record due to the highly disturbed stratigraphy of the lake and to the absence of significant postglacial background sediments between events. The most recent recorded mass-movement is a distinct debris flow sediment layer on the lake floor that was deposited at ~ 1300 cal BP, very shortly after a distinct large-scale mass-movement event observed across the entire lake basin. The presence of silt layers in gyttja overlying these disturbed units suggests that the region was affected by other seismic events following this event, although no MMDs could be directly related to these layers. [ABSTRACT FROM AUTHOR]

A major mining slope failure occurred in July 2012 on the East wall of the LAB Chrysotile mine in Canada. The major consequence of this failure was the loss of the local highway (Road 112), the main commercial link between the region and the Northeast USA. LiDAR scanning and subsequent analyses were performed and enabled quantifying the geometry and kinematics of the failure area. Using this information, this paper presents the back analysis of the July 2012 failure. The analyses are performed using deterministic and probabilistic limit equilibrium analysis and finite-element shear strength reduction analysis modelling. The impact of pit water infilling on the slope stability is investigated. The impact of the mining activity in 2011 in the lower part of the slope is also investigated through a parametric analysis. [ABSTRACT FROM AUTHOR]

The Charlevoix region, in southeastern Québec, is characterized by a dramatic landscape formed by the junction of the Laurentian Highlands, the Charlevoix Astrobleme and the St Lawrence Estuary. At the Last Glacial Maximum (LGM), the region was completely covered by the Laurentide Ice Sheet (LIS). The complex topography of the region was the stage of many of the major deglacial events of southern Quebec (e.g. Goldthwait Sea Invasion, St Lawrence Ice-Stream, Saint-Narcisse Episode). We present a detailed reconstruction of the pattern of retreat of the LIS in the Charlevoix region based on the interpretation of ice-marginal features (e.g. moraines, fans) and glaciolacustrine landforms and deposits, two extensive field campaigns, and the interpretation of high-resolution 3D digital aerial photographs and LiDAR data. Our results indicate five moraine complexes in the region: the Rochette, the Br^ulée, the Sainte-Anne, the Saint-Narcisse and the Mars-Batiscan complexes. Deltas, fans, finegrained sediments, littoral deposits, drainage breaches and deposits were used to identify 91 palaeo-proglacial lakes. The identification of these lakes and their relation to moraine complexes enabled the reconstruction of six stages of lake development during the Charlevoix deglaciation. The development of proglacial lakes occurred in all types of terrain (highlands, lowlands, transitory levels above marine limit). We conclude that local topography had a decisive effect on promoting both moraine deposition and lake development. We suggest that similar topographical regions (hilly-mountainous) that were affected by major ice-margin stabilizations during glacial retreat should have experience small lakes dominating valleys and topographical lows. [ABSTRACT FROM AUTHOR]

Early warning systems (EWSs) rely on the capacity to forecast a dangerous event with a certain amount of advance by defining warning criteria on which the safety of the population will depend. Monitoring of landslides is facilitated by new technologies, decreasing prices and easier data processing. At the same time, predicting the onset of a rapid failure or the sudden transition from slow to rapid failure and subsequent collapse, and its consequences is challenging for scientists that must deal with uncertainties and have limited tools to do so. Furthermore, EWS and warning criteria are becoming more and more a subject of concern between technical experts, researchers, stakeholders and decision makers responsible for the activation, enforcement and approval of civil protection actions. EWSs imply also a sharing of responsibilities which is often averted by technical staff, managers of technical offices and governing institutions. We organized the First International Workshop on Warning Criteria for Active Slides (IWWCAS) to promote sharing and networking among members from specialized institutions and relevant experts of EWS. In this paper, we summarize the event to stimulate discussion and collaboration between organizations dealing with the complex task of managing hazard and risk related to active slides. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution seismic profiles along with physical and sedimentological properties of sediment cores from the Saguenay (Eastern Canada) and Reloncavi (Chile) Fjords allowed the identification of several decimeter to meter-thick turbidites. In both fjords, the turbidites were associated with large magnitude historic and pre-historic earthquakes including the 1663AD (M>7) earthquake in the Saguenay Fjord, and the 1960 (M 9.5), 1837 (M~8) and 1575AD major Chilean subduction earthquakes in the Reloncavi Fjord. In addition, a sand layer with exoscopic characteristics typical of a tsunami deposit was observed immediately above the turbidite associated with the 1575AD earthquake in the Reloncavi Fjord and supports both the chronology and the large magnitude of that historic earthquake. In the Saguenay Fjord, the earthquake-triggered turbidites are sometimes underlying a hyperpycnite associated with the rapid breaching and draining of a natural dam formed by earthquake-triggered landslides. Similar hyperpycnal floods were also recorded in historical and continental geological archives for the 1960 and 1575AD Chilean subduction earthquakes, highlighting the risk of such flood events several weeks or months after main earthquake. In both fjords, as well as in other recently recognized earthquake-triggered turbidites, the decimeter-to meter-thick normally-graded turbidites are characterized by a homogeneous, but slightly fining upward tail. Finally, this paper also emphasizes the sensitivity of fjords to record historic and pre-historic seismicity. [Copyright &y& Elsevier]

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 movements. In this paper, in situ block size distributions of the intact rock mass and the debris deposits are presented and analyzed for nine rock avalanches, five in the Canadian Rocky Mountains and four in the European Alps. Degrees of fragmentation are estimated from these data. Two methods are examined to assess fragmentation energy, one based on the comminution theory, and one on the blasting energy used in the mining industry. The results show that, for the studied rock avalanches, there is a relationship between the reduction in diameter ratio, Rr = D50/d50 (where D50 and d50 are the mean diameter of the intact rock mass and the mean diameter of the debris, respectively), and the potential energy per unit volume normalized with respect to the point load strength of rock (γHG/σc), where γ is the unit weight of the material, HG is the vertical distance between the centres of gravity of the mass at the start and end positions, and σc is the point load strength). For the cases studied, fragmentation energy calculations average 20% of the potential energy. An empirical relationship between Rr and γHG/σc has been established and is used in the definition of a disintegration index (ID). This index seems to reflect the physics of the disintegration process, since it accounts for the fact that the reduction in diameter ratio is a function of the dissipated energy and the strength of the rock. These factors have long been known to affect fragmentation but have never been presented in a coherent manner for rock avalanches. [ABSTRACT FROM AUTHOR]