Combined Geophysical, Geological and Geotechnical Study of Offshore Soft Sediments at a Planned Wind farm Area

Offshore energy production increases rapidly on the Finnish west coast. Effective ground investigation methods are needed for offshore wind farm construction and cable route planning. This study identified fine-grained local subsurface sediment units based on seismoacoustic survey and sediment coring complemented with geotechnical properties from free fall cone penetrometer tests. The finegrained sediments in the study area consist of brackish-water mud, postglacial lacustrine clay and glaciolacustrine clay and silt which all show variability in physical properties and undrained shear strength profile. The study shows that free fall penetrometer tests provide a ground-truth for the seismoacoustic profile interpretation and, combined with seismoacoustic survey and sediment coring enable a fast and cost-efficient site reconnaissance.