The potential vulnerability of the monopile foundation for the offshore structures during seismic events is a valuable research topic. In this study, an integrated 3-D numerical model is set up to investigate the dynamic behavior of monopile-seawater-seabed coupling system in the frequency domain. The pile is considered as linear viscoelastic material and Biot model is used for porous seabed. The dynamic interactions among various components including pile, seabed, and seawater, are fully considered and the perfectly matched layer is adopted as an absorbing boundary condition. The seismic responses of the coupling system, such as hydrodynamic pressure of seawater, pore pressure in seabed, acceleration amplitudes in pile and seabed, are discussed. In addition, the transient liquefaction in the seabed around the monopile foundation is investigated. At the first three peak frequencies, transient liquefaction occurs in more than about two-thirds area around the pile, rather than the whole pile circumference. In particular, only less than about two thirds of the soil around the pile could be transiently liquefied along the vertical direction. Additionally, the influences of embedment depth, pile diameter, soil shear modulus, soil damping ratio, and water depth on the earthquake-induced pore pressure around the pile are significant.

地震事件中海上结构单桩基础的潜在脆弱性是一项有价值的 研究 话题。在这项研究中，建立了一个集成的 3-D 数值模型来研究单桩-海水-海底耦合系统在频域中的动态行为。桩被视为线性粘弹性材料，Biot 模型用于多孔海床。充分考虑桩、海床、海水等各构件之间的动力相互作用，采用完美匹配层作为吸收边界条件。讨论了耦合系统的地震响应，如海水动压、海床孔隙压力、桩和海床加速度幅值。此外，还研究了单桩基础周围海床中的瞬态液化。在前三个峰值频率处，桩周围超过三分之二的区域发生瞬态液化，而不是整个桩周。特别是，桩周围只有不到三分之二的土壤可以沿垂直方向瞬时液化。此外，埋设深度、桩径、土体剪切模量、土体阻尼比、水深等因素对桩周地震孔隙压力影响较大。