Study On Vibration And Acoustic Characteristics Of Pipe During Offshore Pile Driving

With the increasing number of marine engineering nowadays,a considerable degree of radiation noise pollution caused by the excitation of pipe pile foundations during the process of pile sinking,and its impact on marine life have become international research hotspots.At present,there is a lack of systematic research on the mechanism of pipe pile vibration and underwater radiation noise in the process of offshore pile driving,which further restricts the development of the general direction of vibration and noise reduction of pile driving.This article mainly proceeds from the following levels step by step,and conducts the research of pipe pile vibration and sound radiation in pile driving engineering from engineering practice to mechanism method and then to innovation: First,this paper numerically calculates the external excitation of the pile driving system.In the process of offshore pile-sinking,wind,currents and waves that act on marine engineering structures in the marine environment are used as the main external stimuli,and standard formulas and STAR-CCM software are used to analyze the external forces on pipe piles under different wind speeds and sea conditions.The empirical formula and numerical simulation results show that: Compared with the hammering system,the external force in the marine environment is secondary,and its impact can be ignored.As a result,the foundation for simplifying and abstracting the pile driving model into a fluid-pipe pile-soil coupling acoustic-vibration theoretical model under no wind and static water conditions is laid.Next,the acoustic and vibration characteristics of the fluid-pipe pile-soil coupling theoretical model are studied.Based on the Sanders shell theory and the Rayleigh-Ritz method,the free vibration equation of the fluid-solid coupling pipe pile under the spring damping distribution is derived;the Duhamel integral is used to calculate the forced vibration response under the axial impact load;The underwater acoustic radiation equation of pipe piles of frequency domain is constructed.After verifying the validity of the above theoretical approximate solutions,the influence of factors such as the presence or absence of fluid,soil stiffness,and soil depth on the inherent characteristics and acoustic and vibration characteristics of the pipe piles are discussed.The study found that the fluid load causes the natural frequency of the pipe pile to decrease,and at the same time,the amplitude of the acoustic and vibration response becomes smaller;the radial stiffness of the soil has the greatest influence on the acoustic and vibration response of the pipe pile,and the increase in stiffness increases the natural frequency of the pipe pile.The peak of the acoustic vibration response shifts to high frequencies,and the amplitude decreases.Then,the acoustic and vibration test of the pipe pile sinking reduction ratio model was carried out.Completed the modal test of steel pipe piles and composite pipe piles in the air,as well as the forced vibration and sound radiation tests in the anechoic pool and other underwater soiled environments,and guided and corrected the theoretical analytical solutions based on the test results;Innovatively carried out the sound and vibration test of the new type of double-shell steel pipe pile and composite material pipe pile.Compared with the traditional single-layer pipe pile,it has proved that it has a good noise reduction effect.Finally,a numerical study on the radiation noise of a new type of double-shell pipe pile was carried out.On the basis of the test results,the pile-sinking noise control strategy was provided,a new type of low-noise double-shell pipe pile was established,and the finite element numerical simulation and optimization were carried out through COMSOL Multiphysics software,and the geometry of the pipe pile and the composite material’s properties are analyzed by parameterization,and the influence law of the shell change on the overall sound radiation of the pipe pile is obtained.Numerical simulation results show that the change of the radius and wall thickness of the isotropic steel pipe pile has little effect on the noise reduction effect.When orthotropic fiber-reinforced composite materials are used,the noise is minimal when the ply angle is parallel to the axial direction.When the number of layers is reduced,the radiation noise will also be reduced accordingly.In this paper,through theoretical methods,numerical calculations,and experimental tests,the acoustic and vibration characteristics of pipe piles during offshore pile sinking are studied,and the inherent characteristics and acoustic and vibration characteristics of pipe piles under fluid-solid coupling and pile-soil interaction are obtained.The law and the constructed theoretical model,and the proposed new low-noise pipe pile configuration have certain engineering value in the practice and application of vibration and noise reduction in pile-sinking engineering.