Mooring Line-Seabed Interaction considering Trench Development and its Application in Integrated Analysis of Floating Wind Turbines

Offshore floating wind turbine (FWT) provides an efficient solution to address climate challenge. Integrated analysis of FWT is vital to reduce the uncertainties in design and save costs.

In the field, seabed trenches dramatically increase the failure risks of mooring system and raise operation and maintenance costs.

However, the mooring line-seabed interaction related to soil erosion and trench development is not considered in design code (DNVGL-ST-0119, 2018).

Thus, two objectives of this project are: 1. reveal the trigger factor for seabed trenching due to the mooring line-soil interaction; simulate the trench development with time. 2. establish the macro element model considering seabed trenching process; integrate the model into the integrated analysis tool of FWTs, e.g., SESAM.

A total of 3 packages are designed comprehensively. In the seabed trenching package, conduct 1g erosion test to reveal the trigger factor for seabed trenching (WP1.1). Then propose the soil erosion model based on analytical analysis based on 1g erosion test (WP1.2). Finally, the trench development will be simulated by the trench profile model (WP1.3).

In the mooring line-seabed package, get the chain resistance by 1g result (WP2.1); establish the macro element model (WP2.2); considering seabed trenching process, which can consider the soil degradation, erosion, removal (WP2.3). In integrated analysis package, integrate the model into the integrated analysis tool of FWTs, e.g., SESAM (WP3).

The new development of the soil erosion model, seabed trench model and macro element of mooring line soil interaction are the new computation tool for scientific analysis.

Integrated analysis tool for FWT will be an important and powerful tool for FWT analysis considering mooring line-soil interaction, which will contribute to standards’ setting. This will be a groundbreaking progress and will fill the gaps in the norms and standards (DNVGL-ST-0119).