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TitleInfluence of surficial crusts on the development of spreads and flows in eastern Canadian sensitive clays
AuthorPerret, D; Therrien, J; Locat, P; Demers, D
SourceGeo St. John's 2019; by Canadian Geotechnical Society; 2019 p. 1-9
Alt SeriesNatural Resources Canada, Contribution Series 20190134
MeetingGeo St. John's 2019: Canadian Geotechnical Conference; St. John's; CA; September 29 - October 3, 2019
File formatpdf (Adobe® Reader®)
ProvinceQuebec; Ontario
NTS12L; 21L; 21M; 22C; 22D; 31F; 31G; 31H; 31I
AreaSt. Lawrence River; Havre-Saint-Pierre; Lac St-Jean; Saguenay River; Montreal; Ottawa; Gatineau
Lat/Long WENS -77.0000 -63.0000 51.0000 45.0000
Subjectssurficial geology/geomorphology; geophysics; landslides; slope failures; sediments; sensitive clays; geophysical interpretations; shear strength; models; horsts; grabens; rotational landslides; Phanerozoic; Cenozoic; Quaternary
Illustrationsschematic cross-sections; profiles; location maps; digital elevation models; aerial photographs; plots; tables
ProgramPublic Safety Geoscience Eastern Canada Geohazards Assessment Project
Released2019 07 01
AbstractSpreads and flows are the two main types of large retrogressive landslides occurring in Eastern Canadian sensitive clays. In spreads, the soil mass mobilized during failure is dislocated in a succession of horsts and grabens leading to a typical ribbed topography in the landslide scar. The failure mode for flows, on the contrary, is characterized by a succession of rotational slides propagating rearward, which requires that clays liquefy during the movement. These mechanisms are now relatively well understood. However, conditions leading to the development of either a flow or a spread are not yet clearly identified. Some numerical results published in the literature suggest that spreads form preferentially when a non-sensitive crust overlying a sensitive clay deposit is present. We examine in this paper whether this result is supported by observations made on several spreads and flows that occurred in southeastern Ontario and Quebec. It is shown that the presence of a crust is likely not a discriminating factor.
Summary(Plain Language Summary, not published)
Spreads and flows are the two main landslide types occurring in Eastern Canada lowlands where most of the population is concentrated. Processes leading to either spreads or flows are not yet clearly understood. After reviewing 36 well documented landslide cases, new avenues are proposed to identify the main factors controlling the formation of these potentially harmful landslides.

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