Investigation of the Time-Dependent Behavior of Clearwater Clay Shale Using Triaxial Stress Relaxation Tests

Ramin Ghassemi

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

Session: FUNDAMENTALS - IV Soil & Rock Mechanics

ABSTRACT: The time-dependent behavior of argillaceous sediments is known to be a crucial element influencing the long-term operation and safety of the large storage tanks that are currently in use near Fort McMurray, Alberta, Canada. Many of these tanks are constructed on the Cretaceous Clearwater formation, a clay-rich strata with smectite constituting more than 40% of clay fraction, and as a result are quite prone to prolonged settlements. The present study aims to characterize the time-dependent behavior of Clearwater shale using the stress relaxation tests that are much shorter than long conventional creep tests and need fewer samples, and yet describe a similar mechanism. Eight stress relaxation tests were conducted at different axial strain levels in four drained triaxial compression tests on intact samples from each facies. In each triaxial test, the sample was sheared up to a specific axial strain, at which point the axial displacement was kept constant for 40 hours and the reductions in load were recorded. Recorded stresses during different relaxation tests were plotted as normalized deviatoric stress versus logarithm of time. . Calibrated model was implemented in FLAC to simulate performance of a test fill in the field.

RÉSUMÉ: Le comportement différé des sédiments argileux est un facteur important qui influe le bon fonctionnement et la sécurité des grands réservoirs de stockage situés dans la région de Fort McMurray en Alberta au Canada. Nombreux de ces grands réservoirs sont cosmecticte ; donc prévoyant des tassements importants de longue durée. Ce travail vise à caractériser le comportement rtir des tests de relaxation en contrainte. Cette technique, qui nécessite moins mécanisme. On a effectué huit tests de relaxation en contrainte à de différents niveaux de déformation axiale dans des essais chaque essai triaxial était cisaillé à un niveau de déformation axiale spécifié qui est ensuite contraint à rester constant déviatoriques normalisées en fonction du logarithme du temps. Ces résultats expérimentaux sont donc utilisés pour la simuler numériquement le comportement

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