The effects of slab geometries and wave directions on the steep wave-induced soil response and liquefaction around gravity-based offshore foundations

Abstract

Gravity-based offshore foundations generally consist of a bottom slab and one or more cylindrical shafts on top of it. The slab geometry can strongly affect the surrounding flow pattern, dynamic wave pressure distribution and further momentary soil liquefaction. In the present study, the effects of the slab geometry and the incoming wave angle to the foundations on the surrounding soil response are investigated. Gravity-based foundations with bottom slabs of cylindrical shape and hexagonal prismatic shape are considered. For the hexagonal foundation, two different incoming wave angles, i.e. propagating to the hexagon corner and the edge, are simulated. The waves are fully nonlinear steep non-breaking waves. The wave-structure interaction is validated against an existing experiment. Soil consolidation behaviour underneath the foundations is investigated. It is found that both the slab geometry and the incoming wave angle can affect the distributions of pore pressure and momentary liquefaction depth in the surrounding soil.