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TitleInstrumental monitoring, terrain mapping and geophysical investigations of an active landslide near Ashcroft, British Columbia: Tools to better understand, engineer and manage the risks of railway ground hazards
AuthorHuntley, D; Bobrowsky, P; Sladen, W; Zhang, Q; Parry, N; Caston, M; Budd, C; Brasnett, G; Bunce, C; Edwards, T
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 1
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20150017
PublisherGeological Association of Canada
MeetingGAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton; CA; May 21-23, 2014
Documentserial
Lang.English
Mediapaper; on-line; digital
File formathtml
ProvinceBritish Columbia
NTS92I/06; 92I/11
AreaAshcroft; Thomson River
Lat/Long WENS-121.5000 -121.2500 50.7500 50.5000
Subjectsgeophysics; surficial geology/geomorphology; landslide deposits; landslides; geophysical surveys; geophysical interpretations; health hazards; seismic surveys; bedrock geology; radiometric surveys, ground; ground probing radar; seismic surveys, ground
ProgramTerrestrial Landslides, Public Safety Geoscience
LinksOnline - En ligne
AbstractLandslides in the mountain valleys of western Canada have challenged the development and operation of railways since the late 19th Century. In the 21st Century, pronounced economic and environmental repercussions can occur when rail service is disrupted by landslide activity. A vital section of the national railway transportation corridor runs through the Thompson River valley in southern British Columbia. This is a unique area where complex glacial geology, active geomorphic processes and rail infrastructure intersect and are affected by a history of slope instability. To better understand and manage landslide geohazards along this section of the railway corridor, an international multi-year project investigating a small, slow-moving landslide that is adversly impacting CN and CPR infrastructure and operation is now underway. Tracks are lifted and ballast is added when needed during the year to accommodate lateral and vertical displacement across the main body of the slide. Sagging is also observed in a lock-block retaining wall separating the main landslide body and toe. An extensive array of innovative monitoring technologies have now been installed and are monitoring activity across the landslide, including: permanent global positioning stations; piezometers and ShapeAccelArray inclinometry in observation wells; fiber Bragg grating and Brillouin optical time domain reflectometry networks on the retaining wall; InSAR corner reflectors for RADARSAT-2 interferometry; and ground-based SAR and LiDAR. Field observations and surficial geology mapping provide information on the spatial and vertical distribution of earth materials, landforms and geomorphic processes involved in the landslide. Electrical resistivity tomography, electromagnetic (EM-31, EM-34), ground penetrating radar (50 MHz), reflection, and refraction seismic surveys were undertaken to provide insight into the subsurface nature of the landslide. Knowledge of the internal architecture and composition of the landslide as revealed by field mapping and geophysical surveys is essential for interpreting results from the other monitoring programs. All techniques confirm movement across the main body, with the greatest displacement at the south end of the landslide in the vicinity of retaining wall. This is where geophysical surveys indicate a high relief bedrock surface overlain by a 10 m to >60 m thick package of clay, till and saline groundwater-rich gravel, diamicton and bedrock. Planar physical sub-surface features revealed in geophysical profiles include tabular bedding and terrain unit contacts. Profiles also show discrete curvilinear features interpreted as rotational and translational failure planes in clay-rich beds comprising the main body of the slide beneath the rail ballast and retaining wall.
Summary(Plain Language Summary, not published)
A vital section of the national railway transportation corridor runs through the Thompson River valley in southern British Columbia. To better understand and manage landslide hazards along this section of the railway corridor, an international multi-year project is now underway investigating a small, slow-moving landslide that is adversely impacting CN and CPR infrastructure and operation. All techniques confirm movement across the main body, with the greatest displacement at the south end of the landslide in the vicinity of a retaining wall. This is where field mapping and geophysical surveys indicate high relief bedrock overlain by 10 m to >60 m of groundwater-rich sediments. Railway ballast, tracks and retaining wall are sliding along clay-rich beds in the main body of the landslide at depths between 5 and 15 m below surface.
GEOSCAN ID296348