Construction company employs strain gauges in a bid to reduce noise pollution caused by driving foundation piles for wind turbines into the seabed
This noise reduction method used by GBM Works involves fluidising the seabed with water jets, which helps the monopiles sink more quickly and quietly under their own weight. To assess this new system at a site in Maasvlakte, tests were carried out to measure the vibrations and deformations using strain gauges supplied by HBK.
According to Ben Arntz of GBM Works, when a steel foundation pile with a diameter of eight metres is driven, the noise production can reach 180 decibels. The vibration, the pressure waves and the loud noise have a negative effect on underwater life. Therefore regulations have been adopted to reduce the noise production
Under the new method, dozens of water jets inside the pile spray seawater into the seabed. As a result, the seabed takes on properties comparable to those of quicksand. The resistance of the seabed decreases and the foundation pile sinks with the help of a vibratory hammer that replaces the hydraulic piledriving rig.
To assess the success of the method, a series of tests was conducted at 62 test installations to collect information on the vibrations that arise and the effect on noise damping. To measure the strain in the monopoles, GBM Works chose to use strain gauges from HBK. These strain gauges are often used to monitor wind turbines.
“When you exert pressure on steel monopiles, deformation occurs, and vibrations arise that cause noise. We measured those vibrations and also got some interesting information on fatigue in the foundation piles,” explains Arntz.
Most of the data has now been analysed and the noise production of the solution with the vibratory hammer and the jet gun was compared to that of a traditional pile hammer, showing a noise reduction of 90 to 95 percent thanks to the new system.