Influence of surficial crusts on the development of spreads and flows in Eastern Canadian sensitive clays

Didier Perret, Julie Therrien, Pascal Locat, Denis Demers

In the proceedings of: GeoSt. John's 2019: 72nd Canadian Geotechnical Conference

Session: Numerical Modeling of Landslides

ABSTRACT: Spreads 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.

RÉSUMÉ: Les étalements et les coulées sont les deux principaux types de grands glissements de terrain rétrogressifs se produisant des étalements, la masse de sol mobilisée lors de la rupture est disloquée en une succession de horsts et de grabenscicatrices. Le mode de rupture pour les coulées est au contraire caractérisé par une succession de glissements rotationnels identifiées. Certains résultats de modélisations numériques publiés dans la littérature suggèrent que les étalements se Nous regardons dans cet article -probablement pas un facteur discriminant.

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