Sound pressure and particle motion calculations considering pile skin friction

Abstract

Modelling sound propagation over seabeds where the seabed cannot be approximated as an equivalent fluid due to limestone layers with high shear wave speeds is a common underwater acoustic propagation modelling problem for Australian shallow marine environments. With the increase in prospective areas for offshore windfarm development across Australia, construction operations across large regions of the continental shelf area are set to increase. Windfarm construction will require the installation of a large number of foundation piles near potentially sensitive marine habitat areas. Predicting the underwater noise from these activities requires suitable models. This paper investigates the modelling approaches for including a full elastic parameterisation of the seabed when conducting numerical predictions of pile driving sound emissions. The approach considers buried sources and the excitation of shear waves via a skin friction model for the stress–strain relation at the pile-seabed boundary. Shear waves are considered in the source model and in the propagation model. Sound pressure level metrics and particle motion metrics are considered as part of the numerical predictions.