Centrifuge modelling of jackups and spudcans on drained and partially drained silica sand

• Published in: Marine structures 1997, Vol.10 (2), p.221-241
• Main Authors: Dean, E.T.R., Hsu, Y.S., James, R.G., Sasakura, T., Schofield, A.N., Tsukamoto, Y.
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; centrifuge modelling; Centrifuges; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fixed structures and platforms; Fuels; Hardening; Hydraulic constructions; Jack-up rigs; Liquefaction; Marine; Mathematical models; Offshore drilling and production; offshore geotechnics; Port facilities and coastal structures. Lighthouses and beacons; Prospecting and production of crude oil, natural gas, oil shales and tar sands; sand; Silica sand; Stiffness
• ISSN: 0951-8339; 1873-4170
• DOI: 10.1016/S0951-8339(96)00024-X

This paper presents selected data and analyses of centrifuge tests of spudcans and 3-leg independent leg jackup models under fully drained and partially drained conditions on medium dense fine saturated sand. Data of single spudcan models show the importance of vertical displacements in terms of ‘hardening’, and for reducing the potential for liquefaction under cyclic loading. Similarity of loadpaths under conditions of zero vertical displacement during loading at different values of vertical settlement is observed. Data of 3-leg jackup tests indicate that, in the absence of scour, a well-seated flat spudcan on medium dense silica sand can provide considerable rotational stiffness which, however, reduces as cyclic load amplitudes increase. An empirical concept of a ‘fixity ellipse’ is developed. Related analytical studies and experimental work on horizontally-skirted spudcans are also briefly discussed.