ABSTRACT

Suction caissons have become the preferred foundation mooring systems for deep-water oil and gas facilities due to their competitive technical and economical advantages over driven piles and drag embedment anchors. However, several working principles of suction caissons are still not fully understood. These include penetration resistance during both self-weight and suction application, distribution of excess pore pressures induced during installation and their dissipation with time, uplift failure mechanism, displacement associated with the development of vertical pullout capacity, development of passive suction, and the increase in the pullout capacity with time after installation. In order to better understand the behavior of suction caissons installed in normally consolidated and slightly over-consolidated clay, a series of centrifuge tests were carried out at C-CORE's large centrifuge facility. The model caissons were installed in-flight by both self-weight and active suction. This paper presents the centrifuge test results for suction caissons installed in clay. The penetration resistance developed during both caisson's self-weight and suction application are presented. The paper also includes a brief description of C-CORE's centrifuge facility, the clay and caisson models, the multi-function test set-up, and the testing procedure. The preparation of the normally consolidated clay bed foundation in the laboratory and in-flight and the results of the in-flight mini-cone penetration test, used to measure the clay foundation's shear strength, are also presented.

INTRODUCTION

Suction caissons are usually cylindrical units made of steel or concrete. Suction caissons have been used as foundation elements in different seabed soil conditions, such as very soft and soft clay, soft/medium clay, layered clay, and layered clay/sand (Aas and Andersen, 1992). They have been used successfully in the North Sea, the Gulf of Mexico and North-West Shelf in Western Australia (Clukey and Morrison, 1993, Fuglsang and Steensen-Back, 1991).

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