Seismic structure-water-sediment-rock interaction model and its application to immersed tunnel analysis under obliquely incident earthquake

In this study, a transient seismic structure-water-sediment-rock (SWSR) interaction model is proposed to evaluate seismic response of marine structure in ocean space under obliquely incident earthquake, in which the dynamic interaction between structure and its surrounding media, and wave radiation effect of truncated semi-infinite far field domain are fully considered. One particular advantage of the model is that the sediment layer in ocean space is more realistically modelled as fluid-saturated poroelastic medium. Three main procedures are included in establishing the model: first, a finite element equation of near field domain is established to model multimedia interaction; then a viscous-spring absorbing boundary condition is used to simulate wave radiation effect of truncated far field domain; and in the last, equivalent earthquake loading is obtained from seismic free field response. The model can be solved by a standard time integration algorithm such as implicit Newmark's method. The validity of the numerical framework to establish the SWSR interaction model is demonstrated by analyzing three degenerated models and comparing with reference solutions. The seismic SWSR interaction model is finally applied to assess seismic response of an immersed tunnel, with emphasis on the effects of sediment properties here including thickness, porosity and permeability, and the seismic wave incident angle on structural dynamic responses.

Automated summary

This study introduces a novel seismic structure-water-sediment-rock (SWSR) interaction model to effectively assess earthquake response of marine structures under obliquely incident earthquakes in ocean space. The model accounts for dynamic interaction between the structure and surrounding media, as well as wave radiation effects, and is established through multiple procedures with solution using a standard time integration algorithm. Validity of the model is demonstrated through analysis of degenerated models and comparison with reference solutions, and its application to assess seismic response of an immersed tunnel highlights the importance of sediment properties and seismic wave incident angles on dynamic responses.