A case study addressing the development of a novel marine seismic cone penetration testing system.

Abstract

Within the offshore wind sector, following the conclusions of the Pile Soil Analysis (PISA) Project increased emphasis has been placed on the acquisition of in-situ 𝐺𝐺𝑚𝑚𝑚𝑚𝑚𝑚 data, to corroborate laboratory-based measurements, to allow for foundation weight optimization. This requirement for higher fidelity data at all wind turbine locations is coupled with the increased requirement to acquire data in shorter periods to meet ambitious development schedules for offshore wind farms. The development of a deep push seabed SCPT which can be deployed fully autonomously is considered to address this challenge facing the offshore wind industry. Recognising that within the current standards there is a shortfall on what is considered as accurate and reliable data with regards to having confidence in the shear wave velocity (𝑣𝑣𝑠𝑠) measurements obtained offshore, there is a requirement for discussion within the industry; clients, designers and contractors, on how to provide improved set-ups, acquisition and interpretation methods in order to increase the confidence in the 𝑣𝑣𝑠𝑠 data acquired. The case study described within this paper, initiated by such dialog, presents the specification, construction, testing and utilisation of a dual array non-drilling mode seismic cone penetration test (SCPT) device and seismic source to provide demonstrable reliability and accuracy in acquisition and interpretation of in-situ 𝑣𝑣𝑠𝑠 measurements. Within this context, the paper describes; the engineering considerations and optimisation of a novel device intended for deployment from a new generation of robotic vessel; application and limitations of the set-up during trials and offshore operations; commentary on the in-situ data including challenges encountered during interpretation and comparison with existing data acquired at the same location, established correlations and site-specific correlations.

Full Paper