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TitrePreliminary analysis of the failure mechanism at the Nomash River Landslide, Vancouver Island, British Columbia, Canada
AuteurSivak, T J; Brideau, M A; Stead, D; Couture, R; Guthrie, R
SourceGeologically Active: Proceedings of the 11th IAEG Congress; par Williams, A L (éd.); Pinches, G M (éd.); Chin, C Y (éd.); McMorran, T J (éd.); Massey, C I (éd.); 2010 p. 691-699
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100023
Réunion11th IAEG Congress; Aucklaud; NZ; Septembre 5-10, 2010
Lat/Long OENS-127.0000 -126.5000 50.0000 49.7500
Sujetsglissements de terrain; dépôts de glissement de terrain; dépôts de pentes; glissements de pentes; stabilité des pentes; analyses de la stabilité des pentes; géologie de l'ingénieur; géologie des dépôts meubles/géomorphologie
Illustrationslocation maps; stereonets; photographs; diagrams
ProgrammeNational Guidelines for Natural Hazard Assessment and Mitigation, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The Nomash River is situated within a steep-sided valley approximately 6 km northwest of Tahsis, on the northwest coast of Vancouver Island. A 0.3 Mm3 landslide originating on the summit of a 430-m high rock wall failed on April 25th or 26th 1999, destroying a logging road and temporarily blocking the Nomash River. The landslide escarpment contains two crystalline limestone faces of the Quatsino Formation which are crosscut by mafic dykes and sills. The landslide is thought to have been triggered by freeze and thaw cycles over the preceding days. The objective of this study was to identify feasible failure mechanisms based on field data measurements of discontinuity orientations and characteristics. This was accomplished by conducting kinematic, limit equilibrium surface wedge, and block theory analyses. Based on these techniques a wedge failure is the preferred failure mechanism. Geological Strength Index (GSI) estimates and Unconfined Compressive Strength (UCS) values derived from point load testing were used to characterize the rock mass.