Advanced laboratory testing program for the characterization of the stress history, compressibility and shear strength of a glaciolacustrine deposit in Northern Alberta

S Dickinson

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

Session: SOIL AND TERRAIN CHARACTERIZATION - III Geotechnical Laboratory Testing

ABSTRACT: An advanced geotechnical laboratory testing program was carried out to assess the stress history, compressibility and shear strength of an overconsolidated glaciolacustrine clay at the site of a large proposed storage tank farm in Northern Alberta. The program included the performance of 1D consolidation (oedometer) tests, unconsolidated undrained triaxial (UU), Ko-consolidated undrained triaxial (CKoU) and isotropically-consolidated undrained triaxial (CIU) compression tests, in addition to routine index testing. The primary focus of the study was to evaluate the consolidation behaviour of the deposit in order to support tank settlement analyses. Shear strength parameters were also required to support bearing capacity and slope stability analyses. The preconsolidation pressure (p'c) and Overconsolidation Ratio (OCR) of the clay were assessed by means of four independent laboratory approaches. These included (a) interpretation from oedometer tests (b) correlation to undrained shear strength ratio (su/p'o) using a modified-SHANSEP technique, (c) correlation to Plasticity Index (PI) and (d) correlation to Liquidity Index (LI). The p'c of the clay was interpreted to range from approximately 500 kPa at a depth of 2 m to 1100 kPa at a depth of 18 m. The undrained shear strength (su) of the clay ranged from approximately 100 kPa max) and fully softened-fs) of the clay were determined to be 34.1o (at p'=309 kPa) and 26.7o, respectively.

RÉSUMÉ: es essais triaxiaux en compression consolidés au Ko non drainés (CKoU) et des essais triaxiaux en compression consolidés isotropiques non drainés, en plus portement de consolidation du dépôt pour supporter des analyses de tassements des réservoirs de stockage. Les paramètres de résistance au cisaillement étaient aussi nécessaires pour supporter des analyses de capacité portante et de stabilité de talus. La pression de préconsolidation (p'ccorrélation avec le rapport de résistance au cisaillement non drainé (su/p'o) en utilisant la méthode SHANSEP modifiée, rété que la p'c résistance au cisaillement non drainé (supic ('max) de 34.1o (pour p'=309 kPa) et un angle de frottement du sol complètement ramolli ('fs) de 26.7o ont été déterminés.

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