Predicting Peak Resistance of Spudcan Penetrating Sand Overlying Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 140, Issue 2
Abstract
Accurately predicting peak penetration resistance during spudcan installation into sand overlying clay is crucial to an offshore mobile jack-up industry still suffering regular punch-through failures. This paper describes a series of spudcan penetration tests performed on medium-loose sand overlying clay and compares the response to existing centrifuge data from tests performed on dense sand overlying clay. Together these data demonstrate that punch-through is a potential problem for both dense and loose sand overlying clay soil stratigraphies. Using this experimental database, a failure-stress-dependent model has been modified to account for the embedment depth, and the depth of occurrence of is shown to be a function of the sand thickness . The model then was recalibrated, taking these findings into account, for a larger range of material properties and ratios of sand thickness to spudcan diameter (). Finally, the performance of the modified and recalibrated model is verified by comparing its predictions with those calculated using current guidelines. The comparisons show that the modified model yields more accurate predictions of over the range of ratios of practical interest, which when used in practice will potentially mitigate the risk of unexpected punch-through on sand overlying clay stratigraphies.
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Acknowledgments
This work forms part of the activities of the Centre for Offshore Foundation Systems (COFS), which is supported by the Lloyd’s Register Educational Trust as a Centre of Excellence and is now forming one of the primary nodes of the Australian Research Council (ARC) Centre of Excellence in Geotechnical Science and Engineering. This project has received additional support from the Australia-China Natural Gas Technological Partnership Fund and the ARC Discovery program. The authors are grateful for this support and also to drum centrifuge technician Mr. Bart Thompson for his assistance during the experimental work and to Dr. Kok Kuen Lee for providing data on the original dense sand over clay experiments and for fruitful discussions regarding the work.
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© 2013 American Society of Civil Engineers.
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Received: Oct 4, 2012
Accepted: Jul 25, 2013
Published online: Jul 27, 2013
Published in print: Feb 1, 2014
Discussion open until: Apr 18, 2014
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