ABSTRACT
The cone penetration test is the preferred tool for measuring the in-situ soil conditions for offshore wind farm developments. This preference stems from the consistent and reliable data quality, low relative cost, and speed of data acquisition which enables developers to characterise large areas with numerous structure locations to support foundation concept feasibility studies, installation risk assessments and geotechnical engineering analyses to optimise the foundation design by reducing the uncertainty in soil input parameters. However, the interpretation of CPT data is largely dependent on site-specific or published correlations, which can present challenges when relying on the CPT as the primary tool for stratigraphic profiling, interpretation of soil behaviour and for defining geotechnical parameters for engineering design. This paper presents recent developments and processes that enabled the delivery of an optimised CPT based geotechnical design basis for the Dogger Bank Wind Farm. The processes and tools that enabled this approach comprised a novel SI strategy, focussed CPT interpretation and CPT tool development. The strategic approach for the novel SI strategy is presented and the individual elements described. Challenges and limitations associated with the interpretation of CPT data are discussed, including size and scale effects, resolution, calibration with laboratory and large-scale field test data and rate effects. Finally, the challenges with using statistical methods to derive design values from CPT records are briefly discussed.
