Response Characteristics of Seabed Around an Offshore Foundation Structure Subjected to Suction Force

将一种将吸力作用纳入稳定性的带裙边钢沉箱应用于软海底海岸结构，采用先进的沉箱结构-海底相互作用分析方法，模拟了具有吸力的沉箱结构及其软基础在波浪冲击下的动力响应。在本研究中，假定海床是一种流体饱和的孔隙弹性介质，其行为受Biot波传播理论的支配。在不规则波作用下，对有吸力和周围海床的沉箱结构进行了波浪压力作用下的动力响应数值计算。针对海底基础的一些材料特性，数值研究了裙摆长度和吸力对沉箱结构基础动力响应的影响。研究结果总结如下：1)沉箱结构下海床的位移响应很大程度上取决于沉箱结构裙摆长度，从沉箱本身的位移响应可以看出。2)在刚度和横波速度较小的海床上安装吸力沉箱结构时，有必要仔细考虑其位移和相位响应的行为。3)沉箱下孔隙水压力的动力响应在隔室附近达到最大值，并随着离沉箱底部距离的增加而逐渐减小。4)海底基础的孔隙水压力响应不仅取决于作用在沉箱结构裙部的吸力和摩擦力，还取决于其周围海床的刚度。(5)吸力沉箱在软海底是有效的，在海底渗透率较低、提供舱室较多的情况下具有优势。

To apply a steel caisson with skirt, which takes suction effect into the stability, to the coastal structure on soft seabed, dynamic responses of the caisson structure with suction and its soft foundation under wave attack were simulated by an advanced caisson structure-seabed interaction analysis. In this research the seabed was assumed to be a fluid-saturated poroelasic medium whose behavior is governed by Biot's theory of wave propagation. Dynamic responses of a caisson structure with suction and seabed around it were numerically evaluated for wave pressures acting on the front surface of the caisson, which were measured under the irregular wave in the experimental basin. The effects of the skirt length and suction on the dynamic response of caisson structure foundation were numerically investigated for some material properties of seabed foundation.The results obtained in this research is summarized as follows :1)The displacement response of seabed under a caisson structure greatly depends on the skirt length of a caisson structure as seen in the displacement response of a caisson itself.2)It is necessary to give careful consideration to the behavior of both the displacement and phase responses in case of installing a caisson structure with suction on the seabed, whose stiffness and shear wave velocity are small.3)The dynamic response of pore water pressure under caisson has a maximum value in the vicinity of compartments, and also gradually decreases with the distance from the bottom of caisson increasing.4)The pore water pressure response in seabed foundation depends on not only the suction and frictional force acting on the skirt part of a caisson structure but also the stiffness of seabed around it.5)The caisson with suction is effective in soft seabed and has superiority in the cases of the lower permeability of seabed, the more providing compartments.