Personne : Locat, Jacques
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Université Laval. Département de géologie et de génie géologique
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- PublicationAccès libreField performance of four vibrating-wire piezometer installation methods(National Research Council of Canada, 2022-01-12) Young, Nathan Lee; Locat, Pascal; Locat, Ariane; Lemieux, Jean-Michel; Locat, Jacques; Mony, Laura; Leroueil, Serge; Demers, Denis; Germain, AlexandraVibrating wire piezometers provide a number of advantages over the traditional hydraulic piezometer design. There are many methods and configurations for installing vibrating-wire piezometers, with 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 for vibrating wire piezometers at a field site possessing complex stratigraphy, including glacial and marine sediments. Pore pressure data recorded between December 2017 and July 2019 were analyzed to accomplish this objective. Data indicate that SP, MLSP, and FGB piezometers performed well. This determination is based on the fact that piezometers installed at the same depth with these arrangements 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, caused either by shrinkage of the grout or flow occurring along the wires of the embedded instruments. While the FGB-type piezometers used in this study worked correctly, the lack of standard methods concerning both the construction of fully-grouted piezometers is concerning. Furthermore, the lack of a standard method for mixing cement-bentonite grout likely contributed to the failure of the FGCB installations. Thus, due to the lack of guidance for both construction and grout preparation, the use of a bentonite grout removes a degree of uncertainty when fully-grouted installation techniques are used.
- PublicationAccès libreAnalysis of a large rock slope failure on the east wall of the LAB chrysotile mine in Canada : LiDAR monitoring and displacement analysis(2017-04-01) Caudal, Philippe; Grenon, Martin; Locat, Jacques; Turmel, DominiqueA 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 hm3. 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.
- PublicationAccès libreDeterministic and probabilistic stability analysis of a mining rock slope in the vicinity of a major public road : case study of the LAB Chrysotile mine in Canada(National Research Council Canada, 2018-01-18) Amoushahi, Sina; Grenon, Martin; Locat, Jacques; Turmel, DominiqueIn 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.
- PublicationAccès libreHydrogeology of a complex Champlain Sea deposit (Quebec, Canada) : implications for slope stability(National Research Council of Canada, 2020-11-25) Young, Nathan Lee; Locat, Pascal; Delottier, Hugo; Cloutier, Catherine; Locat, Ariane; Lemieux, Jean-Michel; Fortier, Philippe; Locat, Jacques; Leroueil, Serge; Demers, Denis; Germain, AlexandraThe thick sequences of marine clayey deposits which 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 which illustrates the complex groundwater flow system present on site, and shows the importance of including hydrogeologic context in slope stability analysis.
- PublicationAccès libreTsunami generation by potential, partially submerged rockslides in an abandoned open-pit mine : the case of Black Lake, Quebec, Canada(Conseil national de recherches du Canada, 2018-03-12) Leblanc, Jonathan; Locat, Ariane; Grenon, Martin; Harbitz, Carl B.; Locat, Jacques; Løvholt, Finn; Turmel, Dominique; Kim, JihwanThe 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.
- PublicationAccès libreAnalysis of a large rock slope failure on the east wall of the LAB Chrysotile Mine in Canada: back analysis, Impact of water infilling and mining activity(Springer, 2016-10-24) Caudal, Philippe; Amoushahi, Sina; Grenon, Martin; Locat, Jacques; Turmel, DominiqueA 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.
- PublicationAccès libreDevelopment of a long term monitoring network of sensitive clay slopes in Québec in the context of climate change(springer international publishing, 2017-05-24) Locat, Pascal; Cloutier, Catherine; Locat, Ariane; Fortin, Alexis; Lemieux, Jean-Michel; Locat, Jacques; Leroueil, Serge; Demers, Denis; Bilodeau, ChantalThe Government of Québec recently initiated the deployment of a vast groundwater pressures monitoring network in postglacial marine clays to document their variations in time and improve our understanding of the relationship between failure initiation and climate in clay slopes. This project aims at evaluating the impacts of climate change on clay-slope stability and how it can be integrated in landslide risk management to improve public safety. Hydrogeological data will be acquired at sites located throughout the Québec Province’s post-glacial clay deposits to create a public georeferenced index of typical hydrogeological conditions. The project goes beyond the characterization of groundwater pressures and their variations in clay slopes. Indeed, slope deformation will be measured at several sites. Also, two sites in flat terrain will be instrumented in order to evaluate mechanical properties of clay layers in simple 1-D conditions and groundwater recharge. The unsaturated clay crust in slopes susceptible to superficial landslides will be characterized and instrumented. The current lifetime of the monitoring project has been set to a period of 25 years.
- PublicationAccès libreÉtablissement de scénarios d’accélération et de vitesse de grands glissements rocheux actifs : le cas de Black Lake(GEOQuébec, 2015-09-01) Leblanc, Jonathan; Grenon, Martin; Locat, Jacques; Turmel, DominiqueSince 2010, multiple landslides happened in the vicinity of LAB D’Amiante du Canada (LAC) mine (Thetford Mines, Québec, Canada). In 2010, a landslide affected the west wall of the main pit. In July 2012, another landslide affected the South-Eastern portion of the main pit. The 2012 landslide is still active, and a total volume of 50 million m3 may be mobilised. Furthermore, the mine is not anymore in operation, and the water level in the open pit is rising. In the case of a brutal acceleration of the landslide, a wave may be produced. In order to analyse this wave and its potential effects, acceleration and speed scenarios need to be elaborated. A description of the landslide will first be made, followed by the elaboration of speed and acceleration scenarios, based on documented cases and numerical simulations.
- PublicationAccès libreCaractérisation et surveillance d’un glissement rocheux actif d’une mine à ciel ouvert en utilisant le LiDAR(Société canadienne de géotechnique, 2014-06-01) Caudal, Philippe; Grenon, Martin; Locat, Jacques; Turmel, DominiqueEn Juillet 2012, une large rupture de pente s’est produite sur le mur Est de la mine LAB Chrysotile de Thetford Mines Québec, Canada. Cette rupture de pente a eu un impact irrémédiable sur la route régionale située au sommet de la pente, affectant l'économie des communes environnantes. L’objet de cet article est de comprendre ce glissement de terrain en utilisant à la fois le LiDAR à balayage laser terrestre (TLS) et aérien (ALS) . Depuis 2010, trois ALS et douze TLS ont été réalisés pour caractériser et surveiller le glissement. Le balayage laser a d'abord été utilisé pour étudier la géométrie du glissement : son volume, la topographie, la taille et l'orientation de l'escarpement, etc. Il a ensuite été utilisé pour étudier les déplacements 3D pour avoir une meilleure compréhension de la cinématique du glissement. Cet article montre clairement la capacité du balayage LiDAR à fournir des informations quantitatives pertinentes sur la masse rocheuse en mouvement.
- PublicationAccès libreAssessment of the influence of the slope stability conditions of an inactive open-pit mine on the design of a nearby highway(La Société canadienne de géotechnique, 2014-06-01) Amoushahi, Sina; Grenon, Martin; Locat, Jacques; Turmel, DominiqueThis paper presents a review of the literature on the design of public roads in the vicinity of open-pit mines, focusing on the latter's impact on slope stability. It then presents a case study on the design of a major new regional highway along the crest of an abandoned mine in the city of Thetford Mines, Québec, Canada. The first step involved a back analysis of a recent slope failure close to the location of the planned highway in order to derive rock mass properties at the slope scale. Analyses were conducted using the Shear Strength Reduction (SSR) method coupled with finite element (FE) modeling as well as the limit equilibrium analysis (LE) method. Airborne LiDAR surveying results were used in order to calibrate and validate the models. Forward modelling was then performed to assess future slope stability.