A three-dimensional semi-analytical model for the prediction of underwater noise from offshore pile driving
Delft University of Technology
Monday 1 june, 2015, 17:00 - 17:20
0.2 Berlin (90)
In this study, a three-dimensional semi-analytical pile-water-soil interaction model is developed for the prediction of underwater noise from offshore pile driving. The pile is described by a thin shell theory and the hammer is substituted by a force applied at the head of the pile. The soil is modelled as a three-dimensional elastic continuum and the water region is described by the linear acoustic wave equation. The response of the (exterior to the pile) acousto-elastic domain is expressed in terms of a complete set of eigenfunctions which satisfy the surface and interface conditions along the vertical coordinate. The displacement compatibility and the force equilibrium at the pile-water and pile-soil interfaces are satisfied by using the orthogonality relations of the acousto-elastic and shell modes. With the developed model, the wave radiation due to vibratory and impact pile driving is analysed. It is shown that the field generated by impact piling consists of powerful pressure conical fronts in the water column. In the soil region, both shear and compressional waves are generated, with the former being much stronger than the latter. Scholte waves are generated along the seabed-water interface, which induce low-frequency pressure fluctuations in the water column close to the seabed surface. The energy launched by the hammer into the water and into the soil is investigated for both hammer types in order to highlight the main differences regarding the generated wave field. The present work aims to provide the scientific and engineering community with an in-depth physical understanding of the main sources that can possibly contribute to the underwater noise associated with pile driving in offshore environments.
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