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|Title:||Time-Independent and Time-Dependent Behavior of Clearwater Clay Shale Underneath Large Storage Tanks – Laboratory Testing and Numerical Modelling|
|Abstract:||The Clearwater clay shale overlays the Wabiskaw-McMurray bitumen deposit over most of the extent of Athabasca Oil Sands Area in northeastern Alberta, Canada. Both short-term and long-term settlement need to be assessed in a standard foundation design. Accuracy of these assessments depend on the knowledge of the real soil behavior in the field. Therefore, characterizing the behavior of this shale is of prime importance from geotechnical engineering perspective. The goal of this research is to investigate time-independent and time-dependent behavior of Clearwater clay shale in order to develop numerical tools for design, prediction, and analysis of structures over such clay shale formation. To this end, a set of laboratory testing and numerical modeling are completed. An extensive experimental study, including XRD analyses, free swell tests, oedometer tests, constant rate of strain consolidation tests, triaxial tests, and stress relaxation tests, was conducted on various facies of Clearwater Formations (Kcc-710, Kcb-700, Kcb-650, and Kca-625). The results of ten consolidated drained triaxial compression tests and two consolidated undrained triaxial tests were used to determine elastic parameters, Mohr-Coulomb shear parameters, parameters of the Chsoil model to characterize the time-independent response of facies of the Clearwater clay shale. Stress relaxation behavior of facies of the Clearwater clay shale was experimentally examined. Scrutinizing the obtained results, an expression was suggested for stress relaxation of Clearwater clay shale based on the final relaxed normalized deviatoric stress and half relaxation time, the time elapsed for half the stress relaxation in term of stress takes place. Then, a novel application of parameters of stress relaxation test in a model to predict creep settlement was introduced. Hence, a rheological model, the Zener model, was calibrated for facies of the Clearwater clay shale to predict the creep behavior under loading. The results were implemented in FLAC to predict Short-time and Long-time settlement of a test fill constructed on the Clearwater clay shale. The results of short-term analysis were in good agreement with the measured field data and those of the long-term analysis signified the importance of both creep and consolidation phenomena in the settlement assessment.|
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