Environmental Engineering Reference
In-Depth Information
Foundation
pile
Scour
protection
Transition
piece
Turbine
Tower
Nacelle
Rotor blades
Figure 13: Installation sequence of main components for a monopile foundation.
Figure 14: The J-tube through which the power cable is directed to the seabed.
is by pile driving, whereby the foundation pile is driven into the seabed using
hydraulic hammers.
If a foundation pile is designed to be driven into the seabed, a transition piece is
required for the secondary structures such as J-tubes, boat landings and platforms
as shown in Fig. 14.
If the seabed consists of rock, a borehole is prepared (drilled) in which the foun-
dation pile is inserted. Since the foundation does not have to be designed for the
impact forces of pile driving, the secondary structures can be attached directly to
the foundation pile. Hence, no transition piece is needed.
Water currents fl owing around the pile can, through erosion, create a depres-
sion in the seabed around the base of the pile, known as scour. The effect of scour
on the foundation pile is as if it is positioned in deeper water with reduced soil-
penetration depth. The depth of a scour hole depends on local currents and soil
conditions, which is why it cannot be predicted accurately. Furthermore, an
increased section of the pile is exposed to hydrodynamic loads. The increased
length of the unsupported structure above the seabed may also result in a more
dynamic behaviour.
 
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