Effect of Strain Rate and Strain Softening on the Penetration Resistance of Spudcan Foundations on Clay
Publication: International Journal of Geomechanics
Volume 9, Issue 3
Abstract
In practice, natural soils exhibit strain-rate dependency and also soften as they are sheared and remolded. Traditional design approaches, however, have been developed based on idealized rate-independent perfectly plastic soil. This paper presents results for deep penetration of spudcan foundations in strain-softening, rate-dependent, soft clays quantifying the effects relative to results for ideal soil. The analysis was carried out using a large deformation finite-element (LDFE) approach, modifying the simple elastic-perfectly plastic Tresca soil model to allow strain softening, and incorporate strain-rate dependency of the shear strength. Parametric analyses were undertaken varying the strain-rate parameter, the sensitivity and ductility of the soil, the normalized penetration rate, and the soil strength nonhomogeneity. Overall, penetration resistance for rate-dependent, strain-softening clays lay below that for ideal soil. Increased brittleness of the soil led to marked reduction in penetration resistance, only partly compensated by strain-rate dependency. Key results have been presented in the form of design charts, fitted by simple expressions to estimate the limiting cavity depth above the advancing spudcan and the limiting bearing capacity factor at depth.
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Acknowledgments
The first writer is supported by an International Postgraduate Research Scholarship and a University Postgraduate Research Award from the University of Western Australia. The research presented here was undertaken with support from the Australian Research Council through the Discovery and Federation Fellowship programs. The work forms part of the activities of the Centre for Offshore Foundation Systems (COFS), established under the Australian Research Council’s Research Centres Program and currently supported through Centre of Excellence funding from the State Government of Western Australia. This support is gratefully acknowledged, as is the benefit of discussion with Dr. Zarnaz Mehryar and Dr. Hongjie Zhou.
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Information
Published In
International Journal of Geomechanics
Volume 9 • Issue 3 • May 2009
Pages: 122 - 132
Copyright
© 2009 ASCE.
History
Received: Jun 2, 2008
Accepted: Feb 12, 2009
Published in print: May 2009
Published online: May 15, 2009
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