Investigation of large landslides in sensitive clay and what we learned about their failure mechanism
Colloquium
The presentation will describe the investigation of two landslides in sensitive marine clay, with the objective to illustrate the variety of highly retrogressive landslide types in Canada.
The Saint-Fabien landslide occurred in December 1976, 270 km north-east of Quebec City, in glaciomarine sensitive clays covered by peat bog deposits. Unique features of this event are the ground surface and the failure surface that are both close to the horizontal and passive and active failure zones observed in the debris. These features indicate a possible downward progressive failure mechanism, rarely observed in Eastern Canadian clays. The initiation and the propagation of the failure were analysed through 1D numerical modelling using the concept of progressive failure and showed that the concept of progressive failure can explain the extent of this landslide with parameter values obtained from the geotechnical investigation.
On November 2016, a landslide occurred in sensitive glaciomarine sediments near the municipality of Saint-Luc-de-Vincennes, 100 km west of Quebec City. The particularity of this event is that there is evidence that the movement started as a flowslide and then continued as a spread. The investigation of this landslide, enabled to determine the location of the failure surface and to acquire information on the properties of the clay deposit. A combined analysis of the debris was done to reconstruct the different phases of flowing and spreading, and their relative chronologies. The study of this unique landslide gives new insights on the kinematic of highly retrogressive landslides in sensitive clays and strengthens the ones already acquired.
About the speaker: Ariane Locat is currently a Professor at the Department of Civil Engineering and Water Engineering at Université Laval in Quebec. Prof. Ariane Locat’s research focuses on the geotechnical characterization of landslides, the mechanical behavior of soils and the numerical modeling of stresses and deformations during slope movements. She is recognized for her contributions to the understanding of highly retrogressive landslides in sensitive clays. She is the coordinator of the Laboratoire d’études sur les risques naturels, having the mission of improving our knowledge of geohazards and reduce their consequences on populations and infrastructures, both in Quebec, in Canada, and abroad.