The challenges of offshore geotechnical engineering

Design practice in offshore geotechnical engineering grew out of onshore practice, but the two areas have diverged over the last 30 years, driven partly by the scale of the foundation elements used offshore, and partly by fundamental differences in construction techniques. Groups of many moderate sized piles used onshore are replaced by a few very large diameter piles for offshore applications. Similarly excavation of shallow soft sediments is replaced by the use of deep skirts, transferring the effective foundation depth to the level of the skirt tips, or by forcing footings to penetrate several diameters into the seabed; underwater installation has allowed the use of "suction" (or underpressure) to aid installation of skirted foundations and caissons. Emphasis in offshore design is focused more on capacity, paying particular attention to the effects of cyclic loading but generally with less concern on deformations compared with onshore design.