Offshore geotechnical site characterization of silty soils: a novel database

Current practice in the offshore wind industry is to utilise existing CPTU soil behavior charts to identify soil type (e.g., clean sands to silty sands, sand mixtures, clay etc.). The charts identify drained clean sands and undrained clays; however there are limitations detecting silty soils. Accordingly, indication of soil behaviour is needed to define whether the engineering correlations for drained or undrained soils should be used for partial drained silty soils. This paper presents a high-quality database of CPTU and laboratory index data collected as part of a Joint Industry Project on characterisation of silty soils. The database consists of results from 23 sites (21 offshore and two onshore sites) covering a wide range of silts from silty sands to clayey silts and silt mixtures. The database is used to test existing soil behavior charts. The study provides guidelines for industry practice for geotechnical site characterization of silty soils.