Numerical Analysis of T-Bar Penetration in Soft Clay
Publication: International Journal of Geomechanics
Volume 6, Issue 6
Abstract
The penetration resistance of a cylindrical T-bar penetrometer in soft clay is affected by features such as anisotropy, high strain rates, and gradual strain-softening during passage of the T-bar. In order to evaluate these effects, a detailed numerical study has been undertaken, comprising: (1) finite-element analysis; and (2) a strain path approach within the upper bound plasticity mechanism. These studies showed that the T-bar factor is relatively insensitive to the degree of strength anisotropy, provided the penetration resistance is normalized by the average shear strength. Strain rates were found to be six or seven orders of magnitude greater than typical laboratory testing rates, and about three orders of magnitude higher than in a standard vane test. However, the effect of high strain rates is partly compensated by remolding of the soil, where average strains of 400% are imposed on the soil. Charts are presented showing how the separate effects of high strain rates and partial softening may be combined to derive a T-bar factor for a given soil. The paper concludes with a discussion of the measurement of remolded shear strength using cyclic T-bar tests, and interpretation of the T-bar resistance in fully remolded soil.
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Acknowledgments
The writers would like to thank the participants in the joint industry project within which the work described here was carried out, namely: BP Exploration Operating Company, ConocoPhillips, Norsk Hydro, Petroleo Brasileiro, Statoil, and Woodside Engineering. In addition, COFS has been supported under the Australian Research Council’s Research Centres Program while NGI’s participation has been supported by the Research Council of Norway. The writers would also like to acknowledge the guidance from Dr. Lars Andresen, NGI, in connection with the finite-element analyses, and the contribution from Mr. Tom Lunne, NGI, project manager of the joint industry project.
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Published In
International Journal of Geomechanics
Volume 6 • Issue 6 • November 2006
Pages: 411 - 420
Copyright
© 2006 ASCE.
History
Received: Oct 19, 2005
Accepted: Dec 19, 2005
Published online: Nov 1, 2006
Published in print: Nov 2006
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