Incorporating Shank Resistance into Prediction of the Keying Behavior of Suction Embedded Plate Anchors
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 141, Issue 1
Abstract
The suction embedded plate anchor (SEPLA) is a promising deepwater anchoring solution that uses a suction caisson to install a plate anchor vertically to a precise depth within the seabed. The plate anchor is then rotated from its vertical position toward an inclination approximately normal to the load applied by the mooring line in a process known as keying. This configuration reduces the embedment depth and, in typically increasing strength with depth soils, diminishes the installed capacity of the anchor. Therefore, an accurate prediction of the keying behavior of SEPLAs is crucial for offshore operations. Recently, plasticity approaches that combine a yield surface written directly in terms of the applied loads on the anchor with an associated flow rule have been suggested. However, the combined loading yield surface has been defined only for a flat square or rectangular plate. None of these approaches directly account for the resistance of the relatively large anchor shank used to attach the mooring line. The results described in this paper show (1) the impact of the joint plate and shank on the size and shape of the combined loading yield surface and (2) the subsequent impact on predicting the keying behavior of SEPLAs using the plasticity approach. The influence of anchor thickness and shank height on the capacity of an idealized plane-strain anchor is first defined through two-dimensional finite-element (FE) studies. Then, the yield surface parameters for a typical plate and anchor size are provided from three-dimensional FE analysis. The keying behavior of this anchor when subjected to pullout loading from an anchor chain is simulated using the plasticity approach and the results are compared with keying paths for a simple plate anchor without a shank. The predictions using parameters derived from a plate anchor with a shank significantly outperform those using parameters derived from a plate anchor without a shank.
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Acknowledgments
The research presented here was supported by the Australia-China Natural Gas Technology Partnership Fund and the Lloyd’s Register Foundation. The work forms part of the activities of the Centre for Offshore Foundation Systems, currently supported as a node of the Australian Research Council Centre of Excellence for Geotechnical Science and Engineering.
References
ABAQUS 6.11 [Computer software]. Providence, RI, Dassault Systèmes.
Bransby, M. F., and O’Neill, M. (1999). “Drag anchor fluke soil interaction in clays.” Proc., 7th Int. Symp. on Numerical Models in Geomechanics, Balkema, Rotterdam, Netherlands, 489–494.
Bransby, M. F., and Randolph, M. F. (1998). “Combined loading of skirted foundations.” Géotechnique, 48(5), 637–655.
Cassidy, M. J., Gaudin, C., Randolph, M. F., Wong, P. C., Wang, D., and Tian, Y. (2012). “A plasticity model to assess the keying of plate anchors.” Géotechnique, 62(9), 825–836.
Chain and SEPLA Plasticity Analysis (CASPA) 1.2 [Computer software]. Perth, WA, Australia, Univ. of Western Australia.
Dassault Systèmes. (2011). Abaqus analysis user’s manual, Providence, RI.
Dove, P., Treu, H., and Wilde, B. (1998). “Suction embedded plate anchor (SEPLA): A new anchoring solution for ultra-deepwater mooring.” Proc., Deep Offshore Technology 10th Int. Conf. and Exhibition, Deep Offshore Technology, London.
Elkhatib, S. (2006). “The behaviour of drag-in plate anchors in soft cohesive soils.” Ph.D. thesis, Univ. of Western Australia, Perth, WA, Australia.
Elkhatib, S., and Randolph, M. F. (2005). “The effect of interface friction on the performance of drag-in plate anchors.” Proc., Int. Symp. on Frontiers in Offshore Geotechnics, S. Gourvenec and M. Cassidy, eds., Taylor & Francis, London, 171–177.
Gaudin, C., O’Loughlin, C. D., Randolph, M. F., and Lowmass, A. C. (2006). “Influence of the installation process on the performance of suction embedded plate anchors.” Géotechnique, 56(6), 381–391.
Gaudin, C., Simkin, M., White, D. J., and O’Loughlin, C. D. (2010). “Experimental investigation into the influence of a keying flap on the keying behaviour of plate anchors.” Proc., 20th Int. Offshore and Polar Engineering Conf., J. S. Chung, W. C. Kan, E. Fontaine, and J. Chen, eds., Vol. 2, International Society of Offshore and Polar Engineers (ISOPE), Cupertino, CA, 533–540.
Gaudin, C., Tham, K. H., and Ouahsine, S. (2009). “Keying of plate anchors in NC clay under inclined loading.” Int. J. Offshore Polar Eng., 19(2), 135–142.
Gourvenec, S. (2007). “Shape effects on the capacity of rectangular footings under general loading.” Géotechnique, 57(8), 637–646.
Gourvenec, S., Randolph, M., and Kingsnorth, O. (2006). “Undrained bearing capacity of square and rectangular footings.” Int. J. Geomech., 147–157.
Murff, J. D. (1994). “Limit analysis of multi-footing foundation systems.” Proc., 8th Int. Conf. on Computer Methods and Advances in Geomechanics, Vol. 1, Balkema, Rotterdam, Netherlands, 223–244.
Neubecker, S. R., and Randolph, M. F. (1995). “Profile and frictional capacity of embedded anchor chains.” J. Geotech. Engrg., 797–803.
O’Loughlin, C. D., Lowmass, A., Gaudin, C., and Randolph, M. F. (2006). “Physical modelling to assess keying characteristics of plate anchors.” Proc., 6th Int. Conf. on Physical Modelling in Geotechnics, C. W. W. Ng, Y. H. Wang, and L. M. Zhang, eds., CRC Press, Boca Raton, FL, 659–665.
O’Neill, M. P., Bransby, M. F., and Randolph, M. F. (2003). “Drag anchor flukesoil interaction in clay.” Can. Geotech. J., 40(1), 78–94.
Randolph, M. F., Gaudin, C., Gourvenec, S. M., White, D. J., Boylan, N., and Cassidy, M. J. (2011). “Recent advances in offshore geotechnics for deepwater oil and gas developments.” Ocean Eng., 38(7), 818–834.
Skempton, A. W. (1951). “The bearing capacity of clays.” Proc., Building and Research Congress, Vol. 1, London, 180–189.
Song, Z., Hu, Y., O’Loughlin, C., and Randolph, M. F. (2009). “Loss in anchor embedment during plate anchor keying in clay.” J. Geotech. Geoenviron. Eng., 1475–1485.
Taiebat, H. A., and Carter, J. P. (2000). “Numerical studies of the bearing capacity of shallow foundations on cohesive soil subjected to combined loading.” Géotechnique, 50(4), 409–418.
Tian, Y., Cassidy, M. J., and Gaudin, C. (2014a). “The influence of padeye offset on plate anchor re-embedding behaviour.” Géotechnique Lett., 4(1), 39–44.
Tian, Y., Cassidy, M. J., Randolph, M. F., Wang, D., and Gaudin, C. (2014b). “A simple implementation of RITSS and its application in large deformation analysis.” Comput. Geotech., 56(Mar), 160–167.
Tian, Y., Gaudin, C., and Cassidy, M. J. (2014c). “Improving plate anchor design with a keying flap.” J. Geotech. Geoenviron. Eng., 04014009.
Tian, Y., Gaudin, C., Cassidy, M. J., and Randolph, M. F. (2013). “Considerations on the design of keying flap of plate anchors.” J. Geotech. Geoenviron. Eng., 1156–1164.
Tian, Y., Gaudin, C., Randolph, M. F., and Cassidy, M. J. (2014d). “The influence of padeye offset on the bearing capacity of three-dimensional plate anchors.” Can. Geotech. J., in press.
Wang, D., Hu, Y., Randolph, M. F. (2010). “Three-dimensional large deformation finite-element analysis of plate anchors in uniform clay.” J. Geotech. Geoenviron. Eng., 355–365.
Wang, D., Hu, Y., and Randolph, M. F. (2011). “Keying of rectangular plate anchors in normally consolidated clays.” J. Geotech. Geoenviron. Eng., 1244–1253.
Wilde, B., Treu, H., and Fulton, T. (2001). “Field testing of suction embedded plate anchors.” Proc., 11th Int. Offshore and Polar Engineering Conf., International Society of Offshore and Polar Engineers (ISOPE), Cupertino, CA, 544–551.
Yang, M., Aubeny, C. P., and Murff, J. D. (2012). “Behavior of suction embedded plate anchors during keying process.” J. Geotech. Geoenviron. Eng., 174–183.
Yu, L., Liu, J., Kong, X.-J., and Hu, Y. (2009). “Three-dimensional numerical analysis of the keying of vertically installed plate anchors in clay.” Comput. Geotech., 36(4), 558–567.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 141 • Issue 1 • January 2015
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© 2014 American Society of Civil Engineers.
History
Received: Mar 13, 2013
Accepted: Aug 20, 2014
Published online: Sep 17, 2014
Published in print: Jan 1, 2015
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