Penetration and Load Capacity of Marine Drag Anchors in Soft Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 124, Issue 10
Abstract
Marine drag anchors have developed significantly over the past few decades and are capable of providing anchorage loads in excess of 1,000 t. In spite of this progress, the prediction of the load capacity of such anchors has remained almost entirely empirical. A theory developed from geotechnical principles has the potential to give a better understanding of the penetration mechanism and a design method that is portable between different anchor types and sites. This paper presents such a method for the penetration of drag anchors in normally consolidated soils. First, equations are developed to represent the equilibrium forces acting on an anchor at a particular depth below the seabed and at a particular orientation. These equations are based on the proposition that no movement will occur until the soil forces acting parallel to the fluke are overcome. Predictions made using these equations show good agreement with full-scale results. Then a theory is presented that models the movement of the anchor in the soil as the chain or cable is tensioned. Examples of application of this theory show good agreement with nine full-scale tests covering three different sites and five different anchor types.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
American Petroleum Institute (API). (1995). Recommended practice for the design and analysis of stationkeeping systems for floating structures, 1st ed., American Petroleum Institute, Washington, D.C., 28–30.
2.
Baligh, M. M., and Scott, R. F.(1976). “Analysis of wedge penetration in clay.”Geotechnique, 26(1), 185–208.
3.
Bang, S., Taylor, R. J., and Kim, H. T. (1996). “Analysis of anchor mooring lines in cohesive seafloor.”Transp. Res. Rec. Rep. No. 1526, Transportation Research Board, Washington, D.C.
4.
Broms, B. B.(1964). “Lateral resistance of piles in cohesive soils.”J. Soil Mech. and Found. Div., ASCE, 90(2), 27–63.
5.
Butterfield, R., and Bannerjee, P. K.(1971). “A rigid disc embedded in an elastic halfspace.”Geotech. Engrg., Bangkok, Thailand, 2(1), 35–52.
6.
Degenkamp, G., and Dutta, A.(1989). “Soil resistances to embedded anchor chain.”J. Geotech. Engrg., ASCE, 115(10), 1420–1439.
7.
Dutta, A., and Degenkamp, G. (1989). “Behaviour of embedded mooring chains in clay during chain tensioning.”21st Annu. Offshore Technol. Conf., OTC, Houston, Tex., 551–562.
8.
Lee, I. K.(1962). “Bearing capacity of foundations with particular reference to the Melbourne area.”J. Instn. of Engrs., Australia, 34, 283.
9.
Meyerhof, G. G. (1982). The bearing capacity and settlement of foundations. Technical Press, Technical University of Nova Scotia, Halifax, Canada.
10.
Naval Civil Engineering Laboratory (NCEL). (1985). Handbook for marine geotechnical engineering. K. Rocker Jr., ed., Naval Civil Engineering Laboratory, Port Hueneme, Calif., 6–13.
11.
Naval Civil Engineering Laboratory (NCEL). (1987). “Drag embedment anchors for Navy moorings.”Techdata sheet 83-08R, Naval Civil Engineering Laboratory, Port Hueneme, Calif.
12.
Neubecker, S. R., and Randolf, M. F.(1995a). “The performance of drag anchor and chain systems in cohesive soil.”Marine Res. and Technol., 15(2), 78–95.
13.
Neubecker, S. R., and Randolf, M. F.(1995b). “Profile and frictional capacity of embedded anchor chain.”J. Geotech. Div., ASCE, 121(11), 797–803.
14.
Neubecker, S. R., and Randolf, M. F.(1996). “The performance of drag anchor and chain systems in cohesive soils.”Marine Resour. Technol., 15(2), 78–95.
15.
Omega Marine Services International. (1990). “Joint industry project Gulf of Mexico large scale anchor tests, final report.” Omega Marine Services International, Houston, Tex.
16.
Poulos, H. G., and Davis, E. H. D. (1974). Elastic solutions in soil and rock mechanics. John Wiley & Sons, Inc., London, U.K., 165–180.
17.
Randolf, M. F., and Houlsby, G. T.(1985). “Limiting pressure on a circular pile loaded laterally in a cohesive soil.”Geotechnique, 34(4), 613–623.
18.
Rowe, R. K., and Davis, E. H.(1982). “The behaviour of anchor plates in clay.”Geotechnique, 32(1), 9–23.
19.
Stewart, W. P. (1992). “Drag embedment anchor performance prediction in soft soils.”Proc., 24th Annu. Offshore Technol. Conf., Houston, Tex., 241–248.
20.
Taylor, R. J. (1980a). Conventional anchor tests results at San Diego and Indian Island. Naval Civil Engineering Laboratory, Port Hueneme, Calif.
21.
Taylor, R. J. (1980b). Test data for commercially available drag embedment anchors. Naval Civil Engineering Laboratory, Port Hueneme, Calif.
22.
Vivitrat, V., Valent, P. J., and Pontario, A. A. (1982). “The influence of chain friction on anchor pile behaviour.”14th Annu. Offshore Technol. Conf., Houston, Tex., 163–152.
23.
Vold, R. C., and Eie, J. (1982). “Anchor holding tests in the Norwegian trench.”15th Annu. Offshore Techol. Conf., Vol. 2, Houston, Tex., 149–158.
24.
Vryhof. (1990). Anchor Manual. Vryhof Ankers B. V., Krimpen and Yessel, The Netherlands.
25.
Whitman, R. V., and Richart, F. E.(1967). “Design procedures for dynamically loaded foundations.”J. Soil Mech. Found. Div., ASCE, 93(6), 169–193.
26.
Yen, B. C., and Tofanni, G. D. (1984). “Soil resistance to stud link chain.”16th Annu. Offshore Technol. Conf., Houston, Tex., 479–488.
Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 124 • Issue 10 • October 1998
Pages: 945 - 953
Copyright
Copyright © 1998 American Society of Civil Engineers.
History
Published online: Oct 1, 1998
Published in print: Oct 1998
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.