With the development of the offshore oil and gas industry, mobile jack-updrilling platforms are increasingly required to operate in deeper waters andharsher environments. The improvement of the jack-up site-specific assessmentpractice is vital for safely meeting this demand. In soft clayey seabeds, thespudcan foundations of the jack-up platform penetrate deeply into the soil, andcomplete or partial backflow occurs. In recent years, a number of studies haveinvestigated the performance of spudcan foundations in soft clay to improve therelevant recommendations in the industry guideline published by SNAME. In thispaper, a brief review of recent research in this area is first provided. Then,a force-resultant model that is suitable for performing integratedsoil-structure analysis is proposed. An example of the application of thismodel is finally provided, and important comparisons with the SNAME model aredrawn.
Although they were originally designed and built for shallow waters, mobilejack-up platforms are now more broadly used for offshore drilling activities.Due to the development of the offshore oil and gas industry, the demand forjack-ups to operate in deeper waters and harsher environments has increased,requiring improved site-specific assessment practices for both economical andsafety considerations. In many offshore areas, such as the Gulf of Mexico, theseabed consists of soft clayey soil, which often features an increasingundrained shear strength profile with a small intercept at the seabed surface.Jack-up installation in such soil conditions often results in significantfoundation embedment; embedments up to several spudcan diameters are common.The SNAME T&PB 5-5A guidelines are often used by the industry to performsite-specific assessments for the suitability of jack-up platform (SNAME,2008). The recommendations in the SNAME guidelines, however, do not reflect themechanisms of a deeply embedded spudcan in soft clay, but they are derived fromthe observed behavior of shallowly embedded foundations. Conservatism in theSNAME guidelines exists and in practice this can result in an unfavorablesite-specific assessment for a jack-up platform. This paper will brieflyhighlight some recent studies on the behavior of spudcans in soft clay andcompare these to the SNAME guidelines. Then, a plasticity force-resultantfooting model appropriate for spudcans in soft clay is proposed. Examplejack-up analyses with the proposed new model are provided, highlighting thedifferences in prediction with this new model.