The Energy Reduction Factor as a New Parameter to Integrate In Situ Rheological Data in the Numerical Modeling of Sensitive Clay Flowslides

D. Turmel, J. Locat, A. Locat, S. Leroueil, P. Locat, D. Demers

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Landslides in Sensitive Clay

ABSTRACT: Sensitive clays are prone to various types of landslides; among them are flowslides that may affect hectares of land. Debris from those slides has a high mobility, with run out distances that may extent hundreds of meters in relatively flat terrain. Most studies on the mobility use apparent rheological properties in order to back-calculate the behaviour of the landslides. This works well for the back-analyses of landslides, but is of little help in a context of hazard mapping. In this study, real rheological data acquired with a rheometer are used in order to analyse the post-failure behaviour of a flowslide in sensitive clays. A new method, using the destructuration index concept, is used in order to estimate the remaining energy available as kinetic energy for run-out, thus introducing an energy reduction factor. This method is applied on a sensitive clay landslide which took place in Quebec, and where rheological and geotechnical data are available. The numerical modeling of the landslide run-out is done in a full 3D model.

RÉSUMÉ: Plusieurs types de glissements de terrain peuvent survenir dans les argiles sensibles, certains, tel que les coulées argileuses, pouvant affecter de grandes superficies. En effet, la distance de parcours des débris de coulées argileuses peuvent atteindre des centaines de mètres, et ce même sur des terrains ayant une pente très faible. La plupart des études sur la mobilité des coulées argileuses utilisent des paramètres rhéologiques apparents pour pouvoir modéliser à rebours le phénomène, paramètres qui sont très différents des paramètres mesurés en laboratoire. Une nouvelle méthode, basé sur un indice de destructuration , est introduite dans cet article, tridimensionnel, à un glissement ayant eu lieu au Québec.

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