7. Sizing deep foundations

As already mentioned, the search for the best wind conditions means that wind turbines are best sited on higher ground. As a result, sites where geotechnical conditions are conducive to the construction of deep foundations are relatively rare.

In recent years, the number of pile-founded wind turbines has been low (< 5%). The geotechnical contexts that lead to the use of pile foundations are mainly :

• compressible surface soils ;

• karstification or significant alteration at depth.