Development of an enhanced CPT system for Dogger Bank

Abstract

An enhanced seafloor CPT system has been developed to support completion of the soil investigation campaign for Dogger Bank. This enhanced system has a demonstrable and significant performance increase over standard seafloor CPT systems; capable of pushing through dense sand layers with qc>100 MPa and through tens of meters of very stiff clays. At Dogger Bank, this enhanced system has enabled CPT penetrations of more than 40 m below seafloor, in soils where standard systems could only average in the twenties. The system enhancement has been achieved through the application and adaption of techniques well known in the geotechnical industry (water lubrication and water injection), but which have never before been combined in an offshore seafloor CPT system. The performance of the enhanced CPT system has enabled a reliance on seafloor CPTs to acquire data to beyond monopile toe depths, therefore removing absolute reliance on boreholes to acquire data at turbine locations and facilitating the fast and efficient development of a geotechnical design basis.

Development of an enhanced CPT system for Dogger Bank