Field Measurements of Airborne Noise Emission During Impact Piledriving on Land and the Effect of a Reduced Stiffness at the Impact Interface

Impact piledriving is the most common method for pile driving on land. Hydraulic impact hammers are known for their high efficiency due to a very stiff impact with the pile, especially in the case of steel tubular piles, leading to a relatively large impact force and a small impact duration. Pile vibrations are the main source of airborne noise during driving. As noise limits become stricter in the built environment, there is a need for mitigation measures. In this paper we investigate the effect of reduced contact-stiffness of the impact interface on the noise levels in air. To this end, a 90-kJ hydraulic impact hammer is equipped with a novel technology between the hammer ram and the anvil on top of the pile, that consists of a hydraulic spring element. This element reduces the impact force while it lengthens the impact duration. Due to the reduced stiffness, the introduction of the stress wave in the pile is smoother, which is beneficial for noise reduction. The 90-kJ hammer with and without the new technology was used for installation of steel tubular piles, during which the pile driving was monitored, and airborne noise was measured. The noise measurements show significant reduction of the equivalent noise level and the peak noise level when piling with the reduced contact-stiffness, compared with conventional impact piling.