Rana26
Student
- Dec 14, 2022
- 2
An offshore wind developer is planning a large wind farm offshore Virginia. The project is in the concept stage, using monopiles as the preferred foundation option. The water depth varies from 40 to 80 m across the site. You are the geotechnical engineer responsible for providing recommendations to the structural engineer. They have already determined that you would need a 10 m diameter pile to fit the tower diameter requirements for a 15 MW turbine. They have also determined that the wall thickness needs to be minimum of 80 mm with a minimum pile length to diameter ratio of L/D = 3 for structural stiffness purposes. Assume a pile steel density of rs = 7850 kg/m3 and a modulus of Ep = 200 GPa. The soil conditions are shown below, applicable to all problems.
seabed
5 m loose sand (g’ = 8 kN/m3, K = 0.7, d = 25 deg)
40 m of very stiff clay (su = 150 kPa, g’ = 7 kN/m3)
incompressible layer
For the deeper portion of the site (water depth > 60 m), floating turbines are being considered. If the same monopiles were utilized as anchors (loaded in tension) for the floating turbines, at what depth should the mooring line padeye be located to maximize the lateral capacity? Estimate the new axial and horizontal capacity based on your answer, again using the current API method and assuming scour to a depth of 0.5D.
