HR Wallingford is currently conducting physical modelling in its Fast Flow Facility to test the scour development and the performance of a frond mat scour protection system to protect the jacket piles for the East Anglia ONE offshore wind farm.
The company is taking into account the foundation design, the seabed characteristics and metocean conditions.
The East Anglia ONE offshore wind farm, located approximately 30 miles southeast of Lowestoft and entering the construction phase, will comprise 102 turbines, mounted on piled jacket foundations.
Initial tests, undertaken at a scale of 1:2, are some of the largest scour tests ever undertaken in a laboratory, and highlight the power and scale of the Fast Flow Facility, which at 75m long and 8m wide can hold a million litres of water and can generate waves up to 1m high and flows of over 2 m/second, HR Wallingford said.
In the tests, jacket legs are protected with weighted frond mats. The mats are composed of high tensile strength, polypropylene, buoyant, frond lines. The frond mats are designed to mimic naturally formed seaweed, providing additional drag and slowing the flow of water. This reduction in velocity reduces the sediment carrying capacity of the water, resulting in a reduction in the erosion rate of material around the jacket legs, or in deposition.
The weight and time development of sediment build-up of the sediment bank will depend on the local conditions and seabed composition.
A series of three full tidal cycles, including both flood and ebb tides, are being simulated to allow the mats to accumulate sediment. Storm conditions are also being run, in which a 1:1 year, 1:10 year, and 1:50 year storm are simulated.