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Permanent link (DOI): https://doi.org/10.7939/R37659V79

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Characterization of a landslide-prone glaciolacustrine clay from the Thompson River Valley near Ashcroft, British Columbia Open Access

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Other title
Subject/Keyword
direct simple shear
Thompson River Valley
shear strength
landslide
residual
stiff
slope stability
overconsolidated
Ripley
DSS
soil properties
clay
glaciolacustrine
slickenside
ring shear
characterization
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Le Meil, Gael
Supervisor and department
Hendry, Michael T. (Civil and Environmental Engineering)
Examining committee member and department
Deng, Lijun (Civil and Environmental Engineering)
Martin, C. Derek (Civil and Environmental Engineering)
Department
Department of Civil and Environmental Engineering
Specialization
Geotechnical Engineering
Date accepted
2017-07-13T14:16:41Z
Graduation date
2017-11:Fall 2017
Degree
Master of Science
Degree level
Master's
Abstract
Several large landslides have occurred in the Thompson River Valley near Ashcroft, British Columbia. The movement of these landslides have presented challenges for the operation of the two national railways that traverse this valley. The landslides are multiple retrogressive, translational, slow-moving and occur within glaciolacustrine clay. In this study, continuous core samples were collected from the Ripley slide (velocity in the order of 80 mm/year; volume 1.0 × 106 m3) for characterizing the glaciolacustrine clay. The x-ray radiography and logging of the core revealed interbedded silt and clay, interpreted as a glaciolacustrine stratigraphic unit. It includes brown, fat, slickensided clay beds. The glaciolacustrine unit was found to be stiff and heavily overconsolidated (σ’p ≥ 2000 kPa). The objective of the laboratory tests was to characterize the shear behaviour and strength of the glaciolacustrine clay, in particular the pore water pressure response and development of residual shear strength. Direct shear, ring shear and direct simple shear (DSS) tests were conducted. Test results showed that clay-dominated beds have a greater potential for shear strength reduction than silt-dominated beds. Softening and orientation of platy clay particles in the direction of shear reduce the drained shear strength. After large strains were imposed in the direct shear and ring shear tests, slickenside-like shear surfaces were formed in clay-rich samples. At the Ripley slide, clay beds exhibit a low residual friction angle (φr’ = 12°). Low residual shear strength was correlated with high plasticity (LL = 84%). Plastic clay-rich beds are weak soil horizons. Where they are persistent, they are the preferential location for retrogressive failures to occur. Two such clay beds are responsible for the major landslides of the Thompson River Valley. These clay beds were found to host the Ripley slide’s active rupture surfaces (elevations 257.3 and 268.8 m).
Language
English
DOI
doi:10.7939/R37659V79
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
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