Numerical Simulation of Dynamic Response of Seabed and Structure due to the Interaction among Seabed,Composite Breakwater and Irregular Waves (I)

摘要

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading.This excess pore water pressure may reduce effective stress and,consequently,the seabed may liquefy.If liquefaction occurs in the seabed,the structure may sink,overturn,and eventually increase the failure potential.In this study,to evaluate the liquefaction potential on the seabed,numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field.In the condition of an irregular wave field,the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated.Simulation results were used as input data in a finite element computer program for elastoplastic seabed response.Simulations evaluated the time and spatial variations in excess pore water pressure,effective stress,and liquefaction potential in the seabed.Additionally,the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated.From the results of the analysis,the liquefaction potential at the seabed in front and rear of the composite breakwater was identified.Since the liquefied seabed particles have no resistance to force,scour potential could increase on the seabed.In addition,the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater.Due to limitations of allowable paper length,the studied results were divided into two portions;(I) focusing on the dynamic response of structure,acceleration,deformation of seabed,and (II) focusing on the time variation in excess pore water pressure,liquefaction,effective stress path in the seabed.This paper corresponds to (I).