ABSTRACT

Offshore foundation systems are constantly evolving to meet the needs of developments in the energy sector. These developments may be induced by the requirements of moving into ever deeper water for hydrocarbon recovery, or creating foundation systems for renewable energy sources such as offshore wind farms. These massive turbine structures induce complex loading patterns on foundations as the result of combined wind, wave and self weight loading effects, all of which must be accommodated within very small displacement envelopes to allow the turbines to operate. The loading requirements associated with wind turbines are characterised by relatively low vertical loads but high overturning moments. As such, conventional shallow foundations are not well suited to resist these loads, although in some instances gravity base units have been successfully employed. The preferred foundation solution is a monopile. These foundations are attractive because they can be employed in a variety of soil conditions that might exist over the large areas occupied by commercial wind farms.Their design also draws on much offshore geotechnical experience in the design of cyclically loaded piles (e.g. Poulos, 1988).