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 multi-media 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.

本研究提出了一种瞬态地震结构-水-沉积-岩石（SWSR）相互作用模型，以评价斜入射地震作用下海洋空间中海洋结构的地震响应，其中结构与其周围介质和波之间的动态相互作用。充分考虑了截断的半无限远场域的辐射效应。该模型的一个特殊优点是，海洋空间中的沉积物层更现实地建模为流体饱和的多孔弹性介质。建立模型包括三个主要过程：首先，建立了一个近场域的有限元方程来对多媒体相互作用进行建模。然后利用粘滞弹性吸收边界条件模拟截断远场域的波辐射效应。最后，从地震自由场响应中获得等效地震荷载。该模型可以通过标准时间积分算法（例如隐式Newmark方法）求解。通过分析三个退化模型并与参考解进行比较，证明了建立SWSR相互作用模型的数值框架的有效性。地震SWSR相互作用模型最终被用于评估沉管隧道的地震响应，重点是沉积物特性（包括厚度，孔隙率和渗透率）以及地震波入射角对结构动力响应的影响。通过分析三个退化模型并与参考解进行比较，证明了建立SWSR相互作用模型的数值框架的有效性。地震SWSR相互作用模型最终被用于评估沉管隧道的地震响应，重点是沉积物特性（包括厚度，孔隙率和渗透率）以及地震波入射角对结构动力响应的影响。通过分析三个退化模型并与参考解进行比较，证明了建立SWSR相互作用模型的数值框架的有效性。地震SWSR相互作用模型最终被用于评估沉管隧道的地震响应，重点是沉积物特性（包括厚度，孔隙率和渗透率）以及地震波入射角对结构动力响应的影响。