ABSTRACT
Intermediate foundation design usually requires close cooperation between geotechnical and other offshore disciplines, particularly structural engineers. Installation is by dead weight, generally followed by suction assistance. Retrieval and removal are usually by overpressure, possibly with crane assistance. Impact driving, vibratory driving or drilled-and-grouted techniques are sometimes used to achieve high penetrations in competent sand and (weak) rock. Vertical, horizontal, overturning and torsional loads are centric and act at a geotechnical reference point, which is at the midpoint of the foundation at seafloor level. Intermediate suction foundations usually have “stick-up” above seafloor to allow for general seafloor slope, local seabed variations and steel displaced in soil. In addition, platform foundations may have platform leg(s) offset from the foundation midpoint, in order to improve barge transport/barge stability. These features mean that specified loads may not act centrically and at seafloor level.
