New Mechanism-Based Design Approach for Spudcan Foundations on Single Layer Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 135, Issue 9
Abstract
Spudcan foundations for offshore mobile drilling rigs are large saucer-shaped foundations that can penetrate several tens of meters into soft sediments. The penetration depth is typically predicted by considering a wished-in-place foundation at different depths and following traditional bearing capacity approaches to assess the depth at which the estimated capacity matches the applied loading. However, the geometry of the spudcan and its progressive mode of penetration lead to soil failure mechanisms that differ markedly from those relevant to onshore practice. This paper presents a new rational design approach for assessing spudcan penetration in single layer clays based on a study combining centrifuge model testing and large deformation finite-element (FE) analysis. The design approach takes account of the evolving failure mechanisms in the soil, which start with cavity formation and surface heave at shallow penetration, gradually transforming to backflow of soil over the spudcan. A detailed FE parametric study has explored the relevant range of normalized strength, strength nonhomogeneity, and spudcan base roughness, with results validated against centrifuge model test data. The penetration response curves are presented in terms of profiles of bearing capacity factors, forming nondimensional design charts along with simplified expressions for convenient use in practice. Comparisons with approaches suggested in the SNAME design code suggest an urgent need to update current practice.
Get full access to this article
View all available purchase options and get full access to this article.
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, established under the Australian Research Council’s Research Centres Program and currently supported through the Centre of Excellence funding from the State Government of Western Australia. Support from these various organizations is gratefully acknowledged, as is the assistance of the drum centrifuge technician, Mr. Bart Thompson.
References
Ahrendsen, B. K., Dutt, R. N., and Ingram, W. B. (1989). “Jackup footing performance: An integrated approach to geotechnical assessment.” Proc., 21st Offshore Technology Conf., Houston, 525–534, OTC 6027.
Brinch Hansen, J. (1970). A revised and extended formula for bearing capacity, Bulletin No. 28, Danish Geotechnical Institute, Copenhagen, Denmark, 5–11.
Carter, J. P., and Balaam, N. P. (1990). AFENA users’ manual, Centre for Geotechnical Research, Univ. of Sydney, Sydney, Australia.
Cassidy, M. J., Houlsby, G. T., Hoyle, M., and Marcom, M. R. (2002). “Determining appropriate stiffness levels for spudcan foundations using jack-up case records.” Proc., 21st Int. Conf. on Offshore Mechanics and Arctic Engineering, American Society of Mechanical Engineers (ASME), Oslo, Norway, OMAE2002-28085R.
Cox, A. D., Eason, G., and Hopkins, H. G. (1961). “Axially symmetric plastic deformation in soils.” Proc. R. Soc. London, Ser. A, 254, 1–45.
Davis, E. H., and Booker, J. R. (1973). “The effect of increasing strength with depth on the bearing capacity of clays.” Geotechnique, 23(4), 551–563.
Dean, E. T. R. (2008). “Consistent preload calculations for jackup spudcan penetration in clays.” Can. Geotech. J., 45(5), 705–714.
Edwards, D. H., Zdravkovic, L., and Potts, D. M. (2005). “Depth factors for undrained bearing capacity.” Geotechnique, 55(10), 755–758.
Endley, S. N., Rapoport, V., Thompson, P. J., and Baglioni, V. P. (1981). “Prediction of jack-up rig footing penetration.” Proc., 13th Offshore Technology Conf., Houston, 285–296, OTC 4144.
Erbrich, C. T. (2005). “Australian frontiers—Spudcans on the edge.” Proc., 1st Int. Symp. on Frontiers in Offshore Geotechnics, Perth, Australia, Taylor & Francis Group, London, 49–74.
Gemeinhardt, J. P., and Focht, J. A., Jr. (1970). “Theoretical and observed performance of mobile rig footings on clay.” Proc., 2nd Offshore Technology Conf., Houston, 549–558, OTC 1201.
Gemeinhardt, J. P., and Yan, W. K. (1978). “Progress of consolidation of a marine clay in Borneo.” Proc., 10th Offshore Technology Conf., Houston, 1361–1366, OTC 3209.
Ghosh, S., and Kikuchi, N. (1991). “An arbitrary Lagrangian-Eulerian finite element method for large deformation analysis of elastic-viscoplastic solids.” Comput. Methods Appl. Mech. Eng., 86(2), 127–188.
Herrmann, L. R. (1978). “Finite element analysis of contact problems.” J. Eng. Mech., 104(EM5), 1043–1057.
Hossain, M. S., Hu, Y., and Randolph, M. F. (2004a). “Bearing behaviour of spudcan foundation on uniform clay during deep penetration.” Proc., 23rd Int. Conf. on Offshore Mechanics and Arctic Engineering, American Society of Mechanical Engineers (ASME), Vancouver, Canada, OMAE2004-51153.
Hossain, M. S., Hu, Y., Randolph, M. F., and White, D. J. (2005). “Limiting cavity depth for spudcan foundations penetrating clay.” Geotechnique, 55(9), 679–690.
Hossain, M. S., Mehryar, Z., Hu, Y., and Randolph, M. F. (2004b). “Deep penetration of spudcan foundation into NC clay.” Proc., 23rd Int. Conf. on Offshore Mechanics and Arctic Engineering, American Society of Mechanical Engineers (ASME), Vancouver, Canada, OMAE2004-51154.
Hossain, M. S., Randolph, M. F., Hu, Y., and White, D. J. (2006). “Cavity stability and bearing capacity of spudcan foundations on clay.” Proc., Offshore Technology Conf., Houston, OTC 17770.
Houlsby, G. T., and Martin, C. M. (2003). “Undrained bearing capacity factors for conical footings on clay.” Geotechnique, 53(5), 513–520.
Houlsby, G. T., and Wroth, C. P. (1983). “Calculation of stresses on shallow penetrometers and footings.” Proc., IUTAM/IUGG Symp. on Seabed Mechanics, Newcastle, U.K., 107–112.
Hu, Y., and Randolph, M. F. (1998a). “A practical numerical approach for large deformation problems in soil.” Int. J. Numer. Analyt. Meth. Geomech., 22(5), 327–350.
Hu, Y., and Randolph, M. F. (1998b). “ -adaptive FE analysis of elasto-plastic nonhomogeneous soil with large deformation.” Comput. Geotech., 23(1–2), 61–83.
International Organization for Standardization (ISO). (2003). “Petroleum and natural gas industries–Offshore structures—Part 4: Geotechnical and foundation design considerations.” ISO, Geneva, ISO 19901-4.
Lu, Q., Hu, Y., and Randolph, M. F. (2001). “Deep penetration in soft clay with strength increasing with depth.” Proc., 11th Int. Offshore and Polar Engineering Conf., Vol. 2, Int. Society of Offshore and Polar Engineers (ISOPE), Stavanger, Norway, 453–458.
Lunne, T., Myrvoll, F., and Kjekstad, O. (1981). “Observed settlements of five North Sea gravity platforms.” Proc., 13th Offshore Technology Conf., Houston, 305–317, OTC 4146.
Martin, C. M. (2001). “Vertical bearing capacity of skirted circular foundations on Tresca soil.” Proc., 15th Int. Conf. on Soil Mechanics and Geotechnical Engineering, Vol. 1, Int. Society of Soil Mechanics and Geotechnical Engineering (ISSMGE), Istanbul, Turkey, 743–746.
Martin, C. M., and Randolph, M. F. (2001). “Applications of the lower and upper bound theorems of plasticity to collapse of circular foundations.” Proc., 10th Int. Conf. on Computer Methods and Advance Geomechanics, Vol. 2, Tucson, Ariz., 1417–1428.
Noble Denton and Associates. (1987). Foundation fixity of jack-up units: A joint industry study, Noble Denton, London.
Poulos, H. G. (1988). Marine geotechnics, Unwin Hyman, London.
Prandtl, L. (1921). “Eindringungsfestigkeit und festigkeit von schneiden.” Z. Angew. Math. Mech., 1, 15.
Quirós, G. W., and Little, R. L. (2003). “Deepwater soil properties and their impact on the geotechnical program.” Proc., Offshore Technology Conf., Houston, OTC 15262.
Randolph, M. F. (2004). “Characterization of soft sediments for offshore applications.” Proc., 2nd Int. Conf. on Site Characterization, Porto, Portugal, Vol. 1, Millpress Science Publishers, Rotterdam, 209–231 (Keynote Lecture).
Randolph, M. F., Wang, D., Zhou, H., Hossain, M. S., and Hu, Y. (2008). “Large deformation finite element analysis for offshore applications.” Proc., 12th Int. Conf. of Int. Association for Computer Methods and Advances in Geomechanics, Goa, India, 3307–3318.
Rapoport, V., and Young, A. G. (1988). “Foundation performance of jack-up drilling units, analysis of case histories.” Mobile offshore structures, Elsevier Science, New York, 461–476.
Salgado, R., Lyamin, A. V., Sloan, S. W., and Yu, H. S. (2004). “Two- and three-dimensional bearing capacity of foundations in clay.” Geotechnique, 54(5), 297–306.
Skempton, A. W. (1951). “The bearing capacity of clays.” Proc., Building Research Congress, Vol. 1, London, 180–189.
Society of Naval Architects (SNAME). (2002). “Recommended practice for site specific assessment of mobile jack-up units.” T&R Bulletin 5–5A, 1st Ed.–Rev. 2, N.J.
Tani, K., and Craig, W. H. (1995). “Bearing capacity of circular foundations on soft clay of strength increasing with depth.” Soil Found., 35(4), 21–35.
van Langen, H., Wong, P. C., and Dean, E. T. R. (1999). “Formulation and validation of a theoretical model for jack-up foundation load-displacement assessment.” Mar. Struct., 12(4–5), 215–230.
Wang, C. X., and Carter, J. P. (2002). “Deep penetration of strip and circular footings into layered clays.” Int. J. Geomech., 2(2), 205–232.
Young, A. G., Remmes, B. D., and Meyer, B. J. (1984). “Foundation performance of offshore jack-up drilling rigs.” J. Geotech. Engrg., 110(7), 841–859.
Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 135 • Issue 9 • September 2009
Pages: 1264 - 1274
Copyright
© 2009 ASCE.
History
Received: May 20, 2008
Accepted: Dec 31, 2008
Published online: Feb 23, 2009
Published in print: Sep 2009
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.