Development of a geological model and interpretation of soil engineering properties at the site of a proposed tailings impoundment in Northwestern British Columbia

Annie Ruksys

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

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

ABSTRACT: A site investigation program was carried out for the purpose of spatially delineating glaciolacustrine deposits beneath an expanding tailings impoundment in Northern British Columbia. These deposits are of particular concern for tailings dam stability given their potential for exhibiting low shear strength. The surficial geology in this area is unusually complex and has not been investigated by academic or government researchers to the extent that its complexity is understood and documented in published literature. The glacial deposits at this site included ablation till, basal till and glaciolacustrine deposits reflecting at least three phases of glacial advance and retreat. During the last Fraser glaciation, advance phase, glaciers entered the Stikine River Valley from the Boundary Ranges, blocking westward drainage from the Stikine watershed. Obstruction of the Stikine River Valley drainage caused a vast advance-phase glacial lake to form, known as glacial Lake Stikine. The glaciolacustrine silt and clay deposits encountered during the site investigation are associated with Glacial Lake Stikine. A geological model for the site was developed and the engineering properties of the glaciolacustrine deposits were assessed by means of advanced laboratory testing in order to develop a better understanding on site conditions in support of dam design. The laboratory testing focused on the determination of the shear strength, compressibility and preconsolidation pressure (p'c) of the deposits. The laboratory program included the performance of consolidated undrained triaxial compression, direct simple shear and 1D consolidation tests, in addition to routine index testing.

RÉSUMÉ: Une étude de terrain a été conduite dans le but de délimiter des dépôts glaciolacustres situés sous un parc à résidus miniers en expansion dans le nord de la Colombie-la digue à résidus miniers en raison de leur résistance au cisaillement potentiellement faible. La géologie superficielle de à un niveau suffisant pour être publiée ou pour en comprendre la complexité. Les dépôts glaciaires sur le site incluent un re. e Fraser, les glaciers en provenance des Boundary Ranges ont rejoints la vallée de la rivière Stikine a engendrée une vaste avancée lac glaciaire, connu sous le nom de lac glaciaire Stikine. Les dépôts durant géologique du site a été développé et les propriétés géotpour supporter la conception de la digue à résidus miniers. 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'c) du dépôt. Le compression triaxiale, des essais de .

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