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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]

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]

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]

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]

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]

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]

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]

Estimates of submarine channel discharges have been combined with an existing data set of measured fluvial discharges to produce generalized bankfull hydraulic geometry relationships. Previous analysis implies that generalized hydraulic geometry relationships are universal across channels formed under a range of gravity conditions. Here we use data from two different subaqueous channel systems formed by flows with distinct buoyancy characteristics to test whether generalized hydraulic geometry relationships apply in reduced gravity environments where channels tend to have relatively steep slopes. On this basis and assuming formative (bankfull) conditions, we derive estimates of Martian paleodischarges and provide better constrained estimates of Martian paleochannel slopes and flow depths, direct measurements of which are otherwise elusive due to structural deformation and erosion since formation. The steeper slopes in reduced gravity environments tend toward greater Froude numbers at formative discharge conditions; this has implications for bedform dynamics and preservation. [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]

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]