Theoretical study of vibro-acoustics of fluid-pile-soil coupled system and experimental research of noise reduction of small-scale pile driving

Abstract

Excited by a hydraulic hammer, the steel pipe pile makes a quite strong noise, which would cause enormous damage to the hearing of marine mammals. Therefore, a fluid-pile-soil coupled theoretical model is established to predict the environmental impact and underwater noise in pile driving and obtain the near-field acoustic information. Based on the Rayleigh-Ritz theorem, a differential equation of pile vibration that considers soil as a distributed damped spring is derived, and the analytical solution of vibro-acoustic response of pipe pile is given. Then the influence of fluid and soil on natural frequency and sound pressure radiated from pipe pile is discussed. A new type of double-shell pipe pile is also proposed to explore the noise reduction. Several model tests are carried out and compared double-shell with single pipe piles to validate the hypothesis. Numerical results show that the existence of fluid loading causes a decrease in the natural frequency, and when the spring stiffness, especially the radial stiffness, becomes stronger, the sound pressure peaks shift toward higher frequencies. Double-shell pipe piles have good performance in noise reduction as the noise transmission between the inner shell and the outer shell is eliminated.