Abstract

A finite element procedure is utilized to verify the results of a laboratory testing program on suction caisson foundations. A set of model caisson foundations was designed, fabricated, and instrumented for testing in the laboratory under simulated TLP loading. The caissons were made with length-to-diameter ratios of 2, 4, 6, and 12 to study the effect of increasing caisson length on penetration resistance and pullout capacity, as well as the feasibility of using suction as the method of installation. The simulated TLP loading was in the form of static and cyclic tension. Measurements of total foundation capacity, displacements, and pore water pressures inside and in the vicinity of the model caissons were made. The pullout capacity of the model caissons was clearly defined under both drained and undrained loading conditions. Results of the experimental program have shown that the rate of pullout loading had a significant influence on the capacity. The results of the testing program were instrumental in devising a limit equilibrium method to estimate the static pullout capacity of the caissons. The finite element results duplicated the behavior of the model caissons in both the drained and undrained pullout conditions and validated the proposed limit equilibrium design method.

Introduction

Traditionally, suction caissons have been built with length-todiameter (L/D) ratios, or aspect ratios, of approximately 0.5 to 2, e.g., Gullfaks C (Tjeita et aL, 1990), Snorre TLP (Fines et al., 1991; Stove et aL, 1992), Europipe (Tjelta, 1994), etc. These structures are located in the North Sea, the foundation material in the deeper waters is predominantly dense sand and stiff clay. In normally consolidated clay, however, foundation capacity is derived mainly from increased soil shear strength with depth.

This content is only available via PDF.
You can access this article if you purchase or spend a download.