Cone Penetration Testing in Silty Soils (CSi)

Understanding how to measure, classify and characterise silty, partially-drained soils.

Cone penetration testing

Cone Penetration Testing (CPTU) is widely used to assess soil conditions at offshore wind turbine locations. Design standards exist to relate the CPTU results to soil classifications and engineering design parameters in sand and clay soils, but not silts. Similarly, bearing capacities are specified for fully-drained and undrained conditions, but not partially-drained conditions. As the offshore wind industry moves into emerging markets where these silty soils are more common, it is more important than ever to understand their behaviour .

The CSi project aims to:

  • Gather a high-quality database of measured data from silty, partially-drained soils
  • Combine this with data from lab testing and numerical modelling
  • Derive recommendations for investigating and interpreting silty soils and silt mixtures
  • Generate generalised, robust industry guidance for inclusion in future standards

This should allow offshore wind developers to:

  • De-risk foundation design and installation
  • Reduce costs by eliminating unnecessary conservatism

For more information please see Augustesen et al, CSi: A Joint Industry Project into CPTUs in Silty Soils and Fioravante et al, Calibration Cone Penetration Testing in Silty Soils, both presented at the Cone Penetration Testing conference 2022, available from Cone Penetration Testing 2022 | Guido Gottardi, Laura Tonni | Taylor & (

Project end date

March 2023 – initial findings presented at CPT conference on June 2022. 

Project lead



Equinor, RWE, Vattenfall, ScottishPower Renewables, Shell

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Offshore Wind Accelerator (OWA)

Neil Adams

Neil Adams, Project Manager