Underwater Noise from Gentle Driving of Piles

Underwater noise pollution during the installation of foundation piles offshore using large impact hammers can adversely affect marine fauna. In recent years, several vibratory techniques have been developed to drive large foundation piles offshore. One promising technology is called the gentle driving of piles (GDP). This technology uses a combination of high-frequency torsional excitation together with low-frequency vertical excitation at the pile head to drive the pile into the marine sediment. To date, most of the modelling developments have focused on the installation process with this new method, i.e., the development of the so-called driveability models. This paper discusses the underwater noise that is generated during the installation of piles using the GDP method. A case study is analyzed using experimental data to identify the excitation forces at the top of the pile. The prediction of the noise is then investigated using a linear vibroacoustic model in two cases: the classical installation with vertical excitation alone and the installation by means of the GDP method. The differences between the two methods are highlighted, and some conclusions are drawn that can be of added value for practitioners in the field.