Offshore impact pile driving as a source of opportunity for geoacoustic investigations

Abstract

Noise generated by offshore impact pile driving can radiate into and propagate through the air, water, and sediment. Most of the recent studies have focused on predicting acoustic pressure field in water to assess environmental impacts. In this study, we focus on the propagation of acoustic energy along the interface between water and ocean bottom. We modeled the interface wave propagation using the commercial Finite Element (FE) code, Abaqus 6.11. A field test is planned for this summer using a scaled model impact pile driving off the dock in the Bay Campus University of Rhode Island (URI). Interface data (particle velocities at the water-sediment interface) will be collected using the Shear Measurement System. Our efforts will focus on identifying the arrivals corresponding to various wave types using data-model comparison. In addition to the interface waves, we will also model the Mach wave front arrival angle. We will explore the possibility of utilizing the arrival times and angles corresponding to these wave types for setting up an inverse problem. This test will also verify the possibility calculating compressional wave speed using a single three-axis geophone by measuring arrival angle of Mach wave front at the interface generated by impact pile driving. [Work sponsored by the Link Foundation Ocean Engineering and Instrumentation PhD Fellowship program.]