Vibro driving testing in confined space for offshore wind farm application

An onshore vibro driving testing of large-scale piles (2.5 m diameter) was carried out in order to validate an
innovative foundation design that is needed to overcome challenging soil conditions encountered at an offshore wind
farm in France. The foundation concept named DSD (drill-sand-drive) is to replace the hard soils using drilling by
engineered granulars that are then compacted to design density though which monopiles are vibrodriven. Three tests
were conducted covering different levels of soil compaction from low to very high and that was closely controlled
using CPT. The pile driving monitoring comprised PDA sensors, vibro hammer parameters, crane hook load as well
as water pressure along the external pile shaft to evaluate the liquefaction extent. The tests ultimately produced the
confinement configuration induced by the drilled hole and the surrounding stiff soils and provide evidence of its
impact on noticeable amplification of vibro compaction and vibro driving.