Effects of the fluid-solid interface conditions on the dynamic responses of the saturated seabed during earthquakes

In this paper, the effects of the fluid-solid interface conditions between seawater and seabed on the dynamic responses of the seabed during earthquakes are investigated. Based on Biot's porous media theory, a semi-analytical solution of the 1D transient response and an analytical solution of the 1D steady-state response of the saturated seabed under different fluid-solid interface conditions are given, respectively. Based on the transient response solution, it is found that the fluid-solid interface conditions have a significant effect on slow waves and a small effect on fast waves. Based on the steady-state response solution, it is found that the effects of the fluid-solid interface conditions on the displacement amplification factor and pore-water pressure vary under different incident wave frequencies. In the low-frequency region, the lower the interface permeability, the smaller the displacement amplification factor. In the high-frequency region, the lower the interface permeability, the larger the displacement amplification factor. Moreover, the fluid-solid interface conditions affect the dynamic response of the seabed with different permeability coefficients to different degrees. As the seabed permeability coefficient decreases, the effects of the fluid-solid interface conditions on the dynamic responses of the seabed gradually decrease. •Solutions for the seabed with a partially open interface are developed.•The fluid-solid interface has different effects on the two types of P waves.•Effects of the interface on the dynamic response of the seabed are studied.