Integrated Multi-Sonar Inspection of Offshore Wind Foundations and Submarine Cables: A Field Engineering Application

Offshore wind-farm operation requires periodic inspection of turbine foundations and submarine power cables to assess foundation scour, cable surface exposure, and cable burial condition. This paper presents a task-oriented multi-sonar inspection workflow based on multibeam echosounder (MBES), side-scan sonar (SSS), and sub-bottom profiler (SBP) observations for a field engineering application. MBES was used to quantify foundation scour from seabed morphology, SSS to inspect cable surface exposure, and SBP to detect buried cables and estimate burial depth. Processed MBES bathymetry, SSS imagery, and SBP profiles were organized in a common spatial reference so that complementary observations could be associated with the same foundation or cable corridor. The field application was conducted in an operational offshore wind farm in Rushan, Shandong, China, and included 10 wind-turbine foundations and 44 valid SBP cable crossings. The maximum scour depths were 0.8–1.9 m, the maximum local seabed uplift was 0–0.7 m, and no exposed-cable surface signature was identified within the surveyed corridor by SSS. The interpreted burial depths were 1.17–2.56 m, with a mean burial depth of approximately 2.00 m. The field results demonstrate the practical applicability of organizing complementary sonar observations according to task-specific physical observability within a common spatial framework.