Interpretation of Layer Boundaries and Shear Strengths for Soft-Stiff-Soft Clays Using CPT Data: LDFE Analyses
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 142, Issue 1
Abstract
This paper describes a new approach for interpreting cone penetrometer data in soft-stiff-soft clay deposits. The identification of layer boundaries and interpretation of shear strength profile were of particular interest. The proposed approach was based on an extensive parametric study using large deformation finite-element (LDFE) analyses, with a standard cone penetrometer penetrated continuously from the soil surface. The LDFE model has been validated against existing theoretical solutions and numerical results, with good agreement obtained. Regardless of strength ratio between two successive layers, the interface of soft-stiff layers can be identified at ( is the cone diameter) below the kink in penetration resistance curve in the top soft layer. The interface of stiff-soft layers can be demarked at above the kink in the penetration resistance profile in the bottom soft layer. The undrained shear strength of a soft clay layer can be interpreted using a single-layer approach and the resistance profile without the influence of the adjacent stiff layer. The interpretation for the interbedded stiff layer necessitates implementing a correction factor, which is shown to be a function of the thickness and rigidity index of the stiff layer and the strength ratio between that layer and the bottom layer. The proposed design framework is illustrated through a flowchart to be used in practice.
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Acknowledgments
The research presented here was undertaken with support from the Australian Research Council (ARC) Discovery Grant DP140103997. The fourth author is an ARC Discovery Early Career Researcher Award (DECRA) Fellow and is supported by the ARC Project DE140100903. The work forms part of the activities of the Centre for Offshore Foundation Systems (COFS), currently supported as a node of the Australian Research Council Centre of Excellence for Geotechnical Science and Engineering and as a Centre of Excellence by the Lloyd’s Register Foundation. This support is gratefully acknowledged.
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Journal of Geotechnical and Geoenvironmental Engineering
Volume 142 • Issue 1 • January 2016
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© 2015 American Society of Civil Engineers.
History
Received: Dec 13, 2014
Accepted: May 12, 2015
Published online: Jul 6, 2015
Discussion open until: Dec 6, 2015
Published in print: Jan 1, 2016
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