In this paper, the performances of caissons installed by jacking and by suction are compared from the results of a series of centrifuge model tests in normally consolidated kaolin clay. The penetration resistance and radial total stresses at mid-depth of the caisson were measured during both installation and pullout of the caissons. The results showed no essential difference between the penetration resistance of caissons installed by jacking or by self-weight penetration followed by suction, and also the magnitude of total radial stress change was found to be virtually identical for both methods of installation.
Suction caissons are now widely used in the offshore industry for floating anchoring systems, providing vertical resistance for tension leg platforms (Andersen et al. 1993; Clukey et al. 1995). They have been applied successfully in the North Sea, the Gulf of Mexico and the Timor Sea North of Australia (Fuglsang and Steensen-Bach 1991). The installation of suction caissons starts by self-weight penetration which is then followed by pumping out the water from inside the caisson top, thereby creating an under-pressure (referred to here as ‘suction’). The differential pressure created across the caisson lid provides the driving force to install the caisson further. After installation, the top lid is sealed to provide maximum resistance during tensile vertical loading. Recently, the behaviour of suction caissons during installation and vertical pullout has been studied using field tests (Andersen et al. 1993), centrifuge tests (Watson 1999; House et al. 1999; Cao et al. 2002a, Randolph & House 2002) and numerical analysis (Hu et al. 1999; Deng & Carter 2000; Zdravkovic et al. 2001; Andersen & Jostad 2002; Cao et al. 2002b). Prediction of the axial capacity of suction caissons in soft marine clay has tended to be based on conventional design methods used for open-ended driven piles (API-RP2A 1993).
