Installation of Stiffened Caissons in Nonhomogeneous Clays
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 142, Issue 2
Abstract
A significant difference between predicted and measured installation resistance of stiffened suction caissons was identified due to the existing uncertainty regarding the mobilized soil-flow mechanisms. This paper describes an extensive investigation of stiffened-caisson penetration in nonhomogeneous clays undertaken through large deformation finite-element (LDFE) analysis to provide insight into the soil behavior during installation of a caisson. The soil-flow mechanisms around and between stiffeners, and inside and outside of the caisson, and the corresponding penetration resistances were presented from a parametric study, exploring a range of dimensionless parameters related to stiffened-caisson geometry, caisson roughness, and soil strength nonhomogeneity. The LDFE results were compared with centrifuge test data in terms of the soil-flow mechanisms and penetration resistance profile, with good agreement obtained. Three interesting features in the mobilized soil-flow mechanisms inside the caisson were observed: (1) soil started to infill the gap between the bottom two stiffeners when the bottom stiffener penetration reached ( is the critical depth of rotational soil flow around bottom stiffener); (2) soil started to infill the gap between the second and third bottom stiffeners when the second stiffener penetration reached ( is the critical depth of soil backflow into gaps above the 2nd stiffener); (3) profound soil heave due to significant inward flow and the presence of stiffeners and gap between stiffeners. Both and were shown to be a function of the stiffener-width to caisson-diameter ratio, normalized soil strength at the mudline, and soil strength nonhomogeneity. To predict the penetration resistance profile in the field, a rational analytical penetration model, based on the revealed soil-flow mechanisms, was proposed. The LDFE data were used to calibrate the model. Very good agreements were obtained when the proposed model was validated against measured data from field installation and centrifuge tests.
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Acknowledgments
The research presented here was undertaken with support from National Nature Science Foundation of China (No. U1134207 and B13024), the Department of Industry, Innovation, Science, Research and Tertiary Education (DIISRTE) Australia China Science and Research Fund (Group Mission ACSRF00300) and the Australian Research Council (ARC) Discovery Grant (DP1096764). The second 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, as is the benefit of discussion with Dr. Long Yu, Dr. Dong Wang, and Dr. Xu Li.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 142 • Issue 2 • February 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Dec 15, 2014
Accepted: Jun 4, 2015
Published online: Sep 9, 2015
Published in print: Feb 1, 2016
Discussion open until: Feb 9, 2016
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