Geotechnical Stability of Gravity Base Foundations for Offshore Wind Turbines on Granular Soils

Offshore wind energy farms have gained much attention during the last years in Germany and all over the world. In the construction of offshore wind turbines, piled foundations have been mostly used so far. However, gravity base foundations represent a good alternative as they minimize the typical high risks of the offshore works, such as weather-dependent installation, operational safety, construction sequence and performance. The whole wind energy turbine is assembled onshore and promptly transported to the planned location.In the design of the gravity foundation under cyclic loading conditions, it is essential to avoid inadmissibly large reductions of the subsoil bearing capacity due to the excess pore-water pressure (loss of stability) and tilting of the foundation caused by the accumulation of settlements (loss of serviceability).This paper provides a description of the soil-mechanical behaviour of gravity base foundations and gives an account of the current available rules and standards for dimensioning foundations of this type. In this regard, a procedure for the geotechnical design of a gravity base foundation is laid out, where this work points out that the existing standards for designing gravity base foundations need to be further developed. Moreover, a brief summary of the results at a full-scale model test, according to the present state of testing and knowledge, are given.Copyright © 2012 by ASME