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Personne :
Demers, Denis

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Demers

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Denis

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Université Laval. Département de géologie et de génie géologique

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ncf10177916

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  • PublicationAccès libre
    Geophysical and geotechnical characterization of a sensitive clay deposit in Brownsburg, Québec
    (Springer, 2017-05-24) Bélanger, Karine; Locat, Ariane; Fortier, Richard; Demers, Denis
    The results of a geophysical and geotechnical investigation in a sensitive clay deposit affected by numerous landslide scars in Vases Creek Valley near Brownsburg, Quebec, Canada are presented herein. The main objective of this investigation was to assess the suitability of electrical resistivity measurements in marine clay deposits for mapping out areas prone to flowslides. In addition to a 1.6 km-long electrical resistivity tomography (ERT) carried out perpendicular to the axis of the Vases Creek Valley, six piezocone penetration tests and five boreholes with sampling were also performed along the geophysical survey line. Moreover, standard geotechnical parameters and pore water salinity, as well as electrical resistivity of undisturbed clay samples were measured in the laboratory. According to the correlations found between the remoulded shear strength, the pore water salinity and the electrical resistivity, clay samples with salinity below 6.2 g/l are characterized by remoulded shear strength below 1 kPa and electrical resistivity above 2.8 and 10 m measured respectively in the field and in the laboratory. In such conditions, sensitive clay deposits can be prone to flowslides if all other criteria are also met. Based on this resistivity limit value, only one small area of nonsensitive clay was identified in the interpretative stratigraphic cross-section assessed from the field investigation. Otherwise, the deposit is entirely composed of sensitive clay. The ERT is a promising geophysical tool for the delineation of areas prone to large landslides in eastern Canada
  • PublicationAccès libre
    The Saint-Jude landslide of May 10th, 2010, Quebec, Canada : investigation and characterisation of the landslide and its failure mechanism
    (Ottawa National Research Council of Canada, 2017-09-26) Locat, Pascal; Locat, Ariane; Robitaille, Denis; Leroueil, Serge; Demers, Denis; Lefebvre, Guy
    A landslide occurred on May 10, 2010, along the Salvail River, in the municipality of Saint- Jude, Quebec. Debris of the landslide was formed of blocks clay having horst and graben shapes, typical of spreads in sensitive clays. A detailed investigation was carried out by the Ministère des Transports, de la Mobilité durable et de l’électrification des transports du Québec in collaboration with Université Laval, with the objective of characterizing this landslide, determining the causes and learning about its failure mechanism. The soil involved is a firm, grey, sensitive lightly overconsolidated clay with some silt. Data from piezometers installed near the landslide indicated artesian conditions underneath the Salvail River. Cone penetration tests allowed to location of two failure surface levels. The first one starting 2.5 m below the initial river bed and extending horizontally up to 125 m and a second one 10 m higher reaching the backscarp. Investigation of the debris with onsite measurements, light detector and ranging surveys, cone penetration tests, and boreholes allowed a detailed geotechnical and morphological analysis of the debris and reconstitution of the dislocation mechanism of this complex spread.
  • PublicationAccès libre
    The 1994 landslide at Sainte-Monique, Quebec : geotechnical investigation and application of progressive failure analysis
    (Canadian Science Publishing, 2014-09-11) Locat, Ariane; Leroueil, Serge; Fortin, Alexis; Demers, Denis; Jostad, Hans Petter
    In 1994, a landslide occurred in the municipality of Sainte-Monique, Quebec. The debris of the landslide had graben and host shapes, typical of spreads in sensitive clays. The geotechnical investigation shows that the soil involved is a firm to stiff, sensitive, nearly normally consolidated grey silty clay of high plasticity. This soil exhibits a high sensitivity and a high brittleness during shear and is therefore susceptible to progressive failure. Traditional stability analysis cannot explain this landslide. This gives the opportunity to examine the applicability of progressive failure analysis to this spread. Using the finite elements method, it is demonstrated that the initiation and observed extent of the failure surface are explained by a soil having high brittleness during shear and a large-deformation shear strength close to the remoulded shear strength of the soil. The dislocation of the soil mass can also be explained by the active failure occurring in the soil mass above the failure surface during or shortly after failure propagation. It is therefore numerically demonstrated that progressive failure explains the initiation and the extent of the failure surface of this spread.