Study on Dynamic Interaction problems of Seabed-Structure Systems under Waves

海床动力响应是重力式海洋结构物设计的重要课题之一。海床的动力响应是海床-结构-流体系统动力相互作用的结果。针对海床-结构动力相互作用问题，进行了海床动力响应的试验研究和数值分析。通过重力式结构的二维模型试验，研究了波浪作用下超重力流体系统的响应特性水波作用下的孔隙水压力。从理论上建立了求解海床-结构-流体系统动力相互作用问题的边界积分方程。在该分析中，海床被假定为流体饱和的多孔弹性材料。本文假设流体为理想流体，结构物为线弹性体，主要研究结果如下：1）孔隙水压力随海床深度的增加呈指数衰减; 2）孔隙水压力的相位时间随土层深度的增加而变长; 3）数值分析发现，结构物的运动对模型海床的变形、主应力和孔隙水压力都有一定的影响。

The dynamic response of seabed is one of the important subjects for the design of gravity type of offshore structures. The dynamic response of seabed results from the dynamic interactions of the seabed-structure-fluid systems.In this study, an experimental study and a numerical analysis were carried out to evaluate the dynamic response of seabed in terms of a dynamic interaction problem of the seabed-structure-fluid system under water waves.Two dimensional model experiments with the gravity type structure were carried out to determine the response characteristics of the excess pore water pressure under the water waves. From the theoretical point of view, the boundary integral equations were formulated to solve the dynamic interaction problems of the seabed-structure-fluid system. In this analysis, the seabed is assumed as a fluid-saturated poroelastic material. The fluid is assumed to be a perfect fluid and the structure is to be a linear elastic body.The main results of this study are as follows :1) The pore water pressure decreases exponentially as the seabed depth increases.2) As the soil depth increase, the phase time of pore water presure becomes longer.3) It was found that from the numerical analysis, the deformation, principal stresses and pore water pressure in a model seabed were influenced by the motion of a structure associated with wave length.