Critical Skirt Spacing for Shallow Foundations under General Loading
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 139, Issue 9
Abstract
Finite-element limit analysis is used to identify the critical internal skirt spacing for the undrained failure of shallow skirted foundations under conditions of plane strain based on the criterion that the confined soil plug should ideally displace as a rigid block, such that optimal bearing capacity is realized. General loading (vertical, horizontal, and moment) is considered for foundations with skirt embedments ranging from 5 to 50% of the foundation breadth in soil having either uniform strength or strength proportional to depth. The results explicitly identify the number of internal skirts required to ensure soil plug rigidity under arbitrary combinations of horizontal and moment loading expressed as a function of the normalized skirt embedment and the maximum expected level of vertical loading as a fraction of the ultimate vertical bearing capacity. It is shown that fewer internal skirts are required with increasing normalized foundation embedment, but more internal skirts are required with increasing soil strength heterogeneity. The results also indicate the potential for a significant reduction in capacity if insufficient skirts are provided, such that plastic deformation is permitted to occur within the soil plug.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The work described in this paper forms part of the activities of the Special Research Centre for Offshore Foundation Systems (COFS), currently supported as a node of the Australian Research Council Centre of Excellence for Geotechnical Science and Engineering. The work presented in this paper was supported through ARC grant DP0988904. This support is gratefully acknowledged. The work was carried out during an academic visit of the first and second authors to the Department of Engineering Science, University of Oxford, United Kingdom. The support of the Department of Engineering Science and the University of Oxford is gratefully acknowledged. MATLAB scripting advice from Professor David White is also gratefully acknowledged.
References
American Petroleum Institute (API). (2000). “Recommended practice for planning, designing and constructing fixed offshore platforms–Working stress design.” API RP-2A, Washington, DC.
Andersen, K. H., and Jostad, H. P. (1999). “Foundation design of skirted foundations and anchors in clay.” Proc., Annual Offshore Technology Conf., OTC 10824, Houston.
Bransby, M. F., and Yun, G. (2009). “The undrained capacity of skirted strip foundations under combined loading.” Geotechnique, 59(2), 115–125.
Bye, A., Erbrich, C., Rognlien, B., and Tjelta, T. I. (1995). “Geotechnical design of bucket foundations.” Proc., Annual Offshore Technology Conf., OTC 10824, Houston.
Dassault Systèmes. (2009). Abaqus analysis users’ manual version 6.9, Simulia, Providence, RI.
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.
Dyvik, R., Andersen, K. H., Hansen, S. B., and Christophersen, H. P. (1993). “Field tests of anchors in clay. I: Description.” J. Geotech. Eng., 199(10), 1515–1531.
Erbrich, C., and Hefer, P. (2002). “Installation of the Laminaria suction piles – A case history.” Proc., Annual Offshore Technology Conf., OTC 14240, Houston.
Gourvenec, S., Acosta-Martinez, H. E., and Randolph, M. F. (2009). “Experimental study of uplift resistance of shallow skirted foundations in clay under concentric transient and sustained loading.” Geotechnique, 59(6), 525–537.
Gourvenec, S., and Barnett, S. (2011). “Undrained failure envelope for skirted foundations under general loading.” Geotechnique, 61(3), 263–270.
ISO. (2003). “Petroleum and natural gas industries – Specific requirements for offshore structures – Part 4: Geotechnical and foundation design considerations.” ISO 19901-4: 2003, ISO, Geneva.
Kusakabe, O., Suzuke, H., and Nakase, A. (1986). “An upper bound calculation on bearing capacity of a circular footing on a non-homogeneous clay.” Soils Found., 26(3), 143–148.
Makrodimopoulos, A., and Martin, C. M. (2006). “Lower bound limit analysis of cohesive-frictional materials using second-order cone programming.” Int. J. Numer. Methods Eng., 66(4), 604–634.
Makrodimopoulos, A., and Martin, C. M. (2007). “Upper bound limit analysis using simplex strain elements and second-order cone programming.” Int. J. Numer. Anal. Methods Geomech., 31(6), 835–865.
Makrodimopoulos, A., and Martin, C. M. (2008). “Upper bound limit analysis using discontinuous quadratic displacement fields.” Commun. Numer. Methods Eng., 24(11), 911–927.
Mana, D. S. K., Gourvenec, S., and Randolph, M. F. (2010). “A numerical study of the vertical bearing capacity of skirted foundations.” Proc., 2nd Int. Symp. on Frontiers in Offshore Geotechnics (ISFOG), S. Gourvenec and D. J. White, eds., Taylor & Francis, London, 433–438.
Mana, D. S. K., Gourvenec, S., Randolph, M. F., and Hossain, M. S. (2012). “Failure mechanisms of skirted foundations in uplift and compression.” Int. J. Phys. Modell. Geotech., 12(2), 47–62.
Martin, C. M. (2011). “The use of adaptive finite element limit analysis to reveal slip-line fields.” Geotechnique Letters, 1, 23–29.
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. of the Int. Association for Computer Methods and Advances in Geomechanics (IACMAG), Balkema, Rotterdam, Netherlands, 1417–1428.
MOSEK ApS (2010). The MOSEK optimization tools manual, version 5. 〈http://www.mosek.com〉.
Prandtl, L. (1921). “Eindringungsfestigkeit und festigkeit von schneiden.” Angew. Math. U. Mech., 1(15), 15–20 (in German).
Randolph, M. F., and House, A. R. (2002). “Analysis of suction caisson capacity in clay.” Proc., Annual Offshore Technology Conf., OTC 14236, Houston.
Shewchuk, J. R. (2002). “Delaunay refinement algorithms for triangular mesh generation.” Comput. Geom., 22(1–3), 21–74.
Watson, P. G., Randolph, M. F., and Bransby, M. F. (2000). “Combined lateral and vertical loading of caisson foundations.” Proc., Annual Offshore Technology Conf., OTC 12195, Houston.
Yun, G., and Bransby, M. F. (2007). “The undrained vertical bearing capacity of skirted foundations.” Soils Found., 47(3), 493–505.
Information & Authors
Information
Published In
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Jun 19, 2012
Accepted: Dec 18, 2012
Published online: Dec 21, 2012
Published in print: Sep 1, 2013
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.