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TitreRipley Landslide: the geophysical properties of a slow-moving landslide near Ashcroft, British Columbia
TéléchargerTéléchargements
AuteurHuntley, D; Bobrowsky, P; Parry, N; Bauman, P; Candy, C; Best, M
SourceCommission géologique du Canada, Dossier public 8062, 2017, 66 pages, https://doi.org/10.4095/300563
Année2017
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/300563
Mediaen ligne; numérique
Formatspdf
ProvinceColombie-Britannique
SNRC92H/11
Lat/Long OENS-121.5000 -121.2500 50.7500 50.5000
Sujetsglissements de terrain; mouvement de masse; déplacement; moyens de transport; interprétations géophysiques; techniques de cartographie; levés géophysiques; levés acoustiques; bathymétrie; levés électriques; levés de résistivité; résistivité électrique; levés électromagnétiques; levés de la conductivité des terrains; méthodes radar; géoradar; levés de refraction sismiques; etudes des ondes de surface; diagraphie géophysique; trous de mine; diagraphie par rayons gamma; conductivité; susceptibilité magnétique; géologie du substratum rocheux; topographie du substratum rocheux; dépôts glaciaires; tills; dépôts glaciolacustres; argiles; silts; graviers; dépôts fluviaux; dépôts résiduels; blocs; dépôts de glissement de terrain; analyses structurales; analyses stratigraphiques; analyses de la stabilité des pentes; glissements de pentes; eaux de surface; rivières; réseaux hydrographiques; résurgence des eaux souterraines; tendance à l'érosion; surfaces d'érosion; établissement de modèles; modèles; Gestion des risques; géologie des dépôts meubles/géomorphologie; géophysique; géologie régional; stratigraphie; Phanérozoïque; Cénozoïque; Quaternaire
Illustrationslocation maps; photographs; geoscientific sketch maps; borehole logs; tables; models; geophysical profiles; cross-sections; geophysical images; lithologic sections
ProgrammeRisques géo marines, Géoscience pour la sécurité publique
Diffusé2017 05 04
Résumé(disponible en anglais seulement)
Landslide hazards in the Thompson River valley, British Columbia adversely impact vital national railway infrastructure and operations, the environment, cultural heritage features, communities, public safety and the economy. Field investigations and monitoring of the very slow-moving Ripley Landslide, 7 km south of Ashcroft, indicates movement across the main body, with the greater displacement at the south end of the slide near a lock-block retaining wall separating Canadian National (CN) and Canadian Pacific (CPR) rail tracks. Knowledge of the internal composition and structure of the landslide as interpreted through surficial geology mapping and geophysical surveys provide contextual baseline data for interpreting monitoring results and understanding mass-wasting processes in the Thompson River transportation corridor. Bathymetry measurements, electrical resistivity tomography, frequency-domain electromagnetic terrain conductivity, ground penetrating radar, seismic refraction, multi-spectral surface wave analyses, and borehole logging of natural gamma, conductivity and magnetic susceptibility all suggest a moderately high relief bedrock sub-surface overlain by a >20 m thick package of clay, silt, till diamicton and gravel. Planar physical sub-surface features revealed in field observations, geophysical profiles and borehole logs include tabular bedding and terrain unit contacts, in addition to curvilinear-rectilinear features interpreted as sub-horizontal rotational-translational slide surfaces in clay-rich beds beneath the rail ballast and retaining wall at depths between 5 m and 15 m below the surface of the main landslide body. Geophysical data presented support field observations and borehole logs that show sub-surface glaciolacustrine unit boundaries are gradational rather than sharply defined. Geophysical profiles show that clay-rich glacial deposits are the units most likely to contain failure planes. The landslide toe extends under the Thompson River where clay-rich sediments are confined to a >20 m deep bedrock basin. The upper clay beds are armoured from erosion by a lag deposit of modern fluvial boulders except along the west river bank where a deep trough has been carved by strong currents. Waterborne conductivity measurements indicate groundwater discharge at three zones across the submerged landslide toe. Fluvial incision of the submerged toe slope at the south end of the landslide is observed <50 m west of where critical railway infrastructure is at risk. Integrating data from surficial geology mapping and an array of geophysical techniques provided significantly more information than any one method on its own.
Résumé(Résumé en langage clair et simple, non publié)
Le Dossier des rapports sur une enquête de 'Ripley Landslide', 7 km au sud de Ashcroft (Colombie-Britannique). Nouvelles données de cartographie géologique et d'une matrice de techniques géophysiques permettent de mieux comprendre la composition interne et la structure du glissement de terrain. Le Dossier fournit le contexte physique pour l'interprétation des résultats de surveillance récentes et des glissements de terrain dans la compréhension du corridor de transport de la rivière Thompson.
GEOSCAN ID300563