New achievements in underwater noise modelling for offshore pile driving

摘要

Underwater noise emission from pile driving within the offshore wind industry is becoming an increasingly important issue. To advance the understanding and ability to predict underwater noise emissions and associated control measures, Lloyd's Register Consulting and DONG Energy Wind Power have initiated model development activities. Two procedures have been applied. First a technique based on empirical data and long range sound transmission models was successfully evaluated. The prediction is based on a semi-empirical source strength which may be re-used for another site, provided the piling setup is similar. Second, a modelling method was then initiated to account for any hammer and pile configurations and gain knowledge on the near-field sound generation. The method combines two techniques: stress-Wave Equation Analysis for Piles (WEAP) and vibro-acoustic Finite Element (FE). WEAP is a well-established geotechnical tool that calculates the stress wave in the hammer-pile system. A customized WEAP is implemented in order to output soil damping and loading function information. The time-domain FE model is then set up accordingly and predicts acoustic pressure data in the vicinity of the pile. Comparisons to measured hydrophone data are very promising and that bodes well for the next modelling steps.