Characterization of a pre-sheared Glaciolacustrine Deposit beneath a proposed tailings dam in South Central British-Columbia

S Dickinson

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: CASE HISTORIES - I Tailings Dam Site Characterization & Design

ABSTRACT: A site investigation and advanced laboratory testing program was carried out for the purpose of spatially delineating and assessing the engineering properties of a pre-sheared glaciolacustrine silt and clay deposit beneath a tailings dam near Kamloops, British Columbia. Glaciolacustrine sediments were deposited in small glacial lakes that formed in upland valleys marginal to the downwasting ice. The deposit has been subjected to compaction loading, thrusting and shearing due to glacial movements. The laboratory testing focussed on the determination of the shear strength, compressibility and preconsolidation pressure (p'c) of the deposit. The laboratory program included the performance of consolidated undrained triaxial compression, direct simple shear and 1D consolidation tests, in addition to routine index testing, x-ray diffraction and scanning electron microscopy. The peak and fully-softened friction angles of the glaciolacustrine matrix were determined to be 29o and 27o, respectively. The friction angles of the pre-sheared surfaces were determined to range from approximately 8 to 16o, with a mean of 11o. These friction angles were interpreted to reflect the residual shear strength of the high plastic clay laminae on which the pre-shearing had occurred. The p'c of the deposit was estimated to be approximately 400 kPa. The overconsolidation ratio (OCR) of the deposit was interpreted to range from approximately 2 to 4.

RÉSUMÉ: Une étude de terrain et un progrésidus miniers près de Kamloops en Colombie-Britannique. Les sédiments glaciolacustres ont été déposés dans des forces de compression, de poussée et de cisaillement en raison des mouvements glaciaires. Les essais en laboratoire ont été conduits principalement dans le but de déterminer la résistance au cisaillement, la compressibilité et la pression de préconsolidation (p'cclus des essais consolidés et non drainés en compression triaxiale, des essais de cisaillement simple et des essais de frottement au pic de 29o et un angle de frottement du sol complètement ramolli de 27o ont été déterminés pour la matrice glaciolacustre. Des angles de frottement entre environ 8 et 16o ont été déterminés pour les surfaces préalablement cisaillées, avec une moyenne de 11o. Il est interprété que ces angles de frottement représentent la résistance au La p'c du dépôt a été estimée à environ 400 kPa, correspondant à un rapport de surconsolidation (OCR) entre 2 et 4.

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Cite this article:
S Dickinson (2016) Characterization of a pre-sheared Glaciolacustrine Deposit beneath a proposed tailings dam in South Central British-Columbia in GEO2016. Ottawa, Ontario: Canadian Geotechnical Society.

@article{4083_0721054848,author = S Dickinson,title = Characterization of a pre-sheared Glaciolacustrine Deposit beneath a proposed tailings dam in South Central British-Columbia,year = 2016}