Suction anchor installations for deep gulf of mexico applications

摘要

A cost-effective solution to mooring problems in the deep and ultra-deep waters of the Gulf of Mexico (GoM) is the suction anchor system. Suction caisson foundations, also known as skirt piles and bucket foundations, have been used with sucess in the North Sea for major structures such as the Gullfaks C gravity platform (1989), the Europipe fixed steel jacket (1994), and the Snorre tension leg platform (1991). In the normally consolidated cl;ays of the deep GoM, the new foundation concept is implemented with mooring applications where the holding capacity derives from increased resistance with detph to pullout or lateral bearing capcity failure mechanisms. Knowledge of the geotechnical engineerig propoerties of the deep GoM clays is key to accurate and efficient foundation design. An effective way to determining these properties is by way of correlation with actual caisson behavior during installation. The results of a laboratory modeling program of suction caisson installatons are used in conjunction with observations from about half a dozen actual deployments to back-figure the geotechnical properties of the foundation materials. The model caissons were fabricated with length-to-diameter ratios ranging between 2 and 12 to investigate the effect of increasing caisson aspect ratio on the feasibility of effect of increasing caisson aspect ratio on the fesibility of using suction as the method of installation. In the field, the installed caissons had a diameter of 12 ft (3.7 m) and an aspect ratio of 5. The caissons were installed in water depths ranging between 4000 to 10,000 ft (12000 to 3000m). In general, self-eweight penetration accounted for approximately one half the installation depth and the suction penetration data were utilized to sketch profiles of undrained shear strengths with depth at the installation locations.