An accurate frequency-domain model for seismic responses of breakwater-seawater-seabed-bedrock system

Abstract A frequency-domain finite element model is proposed to evaluate seismic response of breakwater-seawater-seabed-bedrock system with full consideration of interactions among them. The frequency-domain model contains near field finite element model, accurate absorbing boundary condition (ABC) and seismic wave input. Firstly, the accurate ABC on the truncated boundaries is applied to simulate the far field of infinite domain. Discretizing for wave equation of the fluid-poroelastic-solid media in the depth direction, and using analytical methods in the remaining coordinate direction, the accurate ABC is mathematically derived without introducing any approximate assumptions. Secondly, the equivalent input seismic loads on the ABC are obtained by one-dimension (1D) response of free field. Combining of the proposed ABC, equivalent input seismic loads, and near field finite element equation, the coupled model to evaluate the seismic response of breakwater-water-seabed-bedrock system is obtained. Numerical examples indicate that the proposed model is accurate and efficient. Finally, the proposed model is used to investigate effects of slope angle of breakwater, water depth and seabed soil properties including seabed porosity, permeability coefficient and shear modulus on seismic response of breakwater, and the momentary liquefaction of seabed.