The lateral capacity of suction caissons and traditional pile elements are evaluated under loading conditions typical of deepwater exploration and production applications. Results from finite element analyses for cohesive and a layered clay-over-sand foundation are presented. The effects of the suction caisson soil-structure interface conditions and modeling assumptions are shown to dramatically affect computed capacities.
Many deepwater floating structure foundations are designed to resist a predominately lateral mooring load. Finite element techniques are used herein to demonstrate responses of two typical foundation elements for deepwater oil exploration and production applications: suction caissons and laterally loaded piles. These foundation elements are analyzed with techniques that account for the significant aspects of responses important to their lateral capacity. Comparisons of the performance of lateral pile elements and suction caissons in a cohesive soil are presented. The ultimate capacities of the two specific foundation elements examined here are roughly the same. Solutions for the lateral capacity of caissons in a layered clay over sand condition are presented.
Sukumaran et al. (1999) and Sukumaran and McCarron (1999) have validated finite element numerical techniques for calculating suction caisson capacities. The following describes some additional work on the effects of interface modelling on the computed responses. The particular aspects of the interface investigated are friction assumptions and separation of the soil from the caisson at the interface. The caisson considered is 15 ft in diameter and 60 fft long (L/D = 4). The finite element program ABAQUS (HKS, 1998) is used for the analyses. The finite element model consists of solid elements for the soil, shell elements for the caisson structure, and interface elements to simulate the soil-structure contact. The contact simulation includes the effects of friction and potential separation of the soil from the structure.
