Laboratory Modeling of Suction Caisson Foundations

Suction caisson foundations (SCF), also known as skirt piles (Tjelta et at., 1990) and bucket foundations (Bye et at., 1995), have been used with success in the North Sea for major structures such as the Gullfaks C (1989) gravity platform, the Europipe fixed steel jacket (1994), and the Snorre (1991) tension leg platform. Insufficient experience in the US with this novel foundation type prompted Shell Oil, in 1993, to utilize conventional pile driving for the Auger platform in the Gulf of Mexico (GoM) (Luyties et at., 1994). World events and the discovery of major petroleum prospects in the deep GoM within the United States Exclusive Economic Zone make it necessary to examine and exploit the new technology for application within this zone. The thrust of this effort is in line with the stated objectives of the Offshore Technology Research Center (OTRC) and our industry partners; specifically the study of the basic engineering problems associated with reducing the costs and improving the structural reliability of structures in water depths of 2000 to 5000 m (6000 to 10,000 ft), in the GoM. The main goal of the project that is the basis for this paper is to study the behavior and pullout capacity of suction caisson foundations. An experimental approach was used in which model caissons were tested under static and cyclic pullout loading. Prior to testing, the program involved the preparation of soil samples, design and manufacture of model suction caissons, and the development of an instrumentation, data acquisition, and loading systems. In this paper, the individual components of the testing program are addressed separately and then combined as the first test series is described. The arrival at the working model and the successful completion of preliminary tests are the major accomplishments of the initial phase of the program. Results of additional load tests are included in a companion paper.