A critical appraisal of methods for and obstacles to obtaining, processing and interpreting useful data from offshore seismic cone penetration testing

The seismic cone penetration test (SCPT) is an essential tool for establishing in-situ shear wave velocity (vs ) and hence Small Strain Shear Stiffness (Gmax ). The technique has received intense attention recently as it is considered the most reliable in-situ tool available to deliver Gmax profiles. These profiles are used to calibrate results of advanced laboratory testing and as direct input for numerical modelling of offshore windfarm foundations. However, although SCPT has been performed routinely on land for many years, the complexities of performing this kind of testing with a seismic source located on the seabed presents ongoing challenges for the industry. Additionally, there remains disagreement amongst the engineering and academic community over the most appropriate data interpretation methods. The lack of standardisation between contractors in equipment capability and arrangements, data deliverables and methods for interpretation can lead to difficulties for practicing engineers in establishing the reliability of the generated data sets. The authors provide a critical review of the acquisition methods utilised and how these affect the quality, volume and validity of the data. An appraisal of the advantages and disadvantages of true interval straight ray path and pseudo interval true ray path processing methodologies is presented along with alternative recommendations for developing design vs profiles.