Abstract: Vertical circular cylinder or group cylinders are widely used in coastal and ocean engineering, which are one of the most common type of the ocean engineering structures. In this paper, based on linear water wave diffraction theory and wave induced seepage consolidation theory ,the analytical solutions to the diffracted water wave-induced seepage pressures referring to porous multiple vertical circular cylinders resting on permeable elastic seabed are derived by applying the eigenfunction expansion approach, and then the wave-induced lift force and overturn moment caused by the seepage pressure on the bottoms of a pair of vertical cylinders are accordingly evaluated and are compared with direct diffracted wave force and moment. The results illustrate that the porosity of the lateral surface of the circular cylinder may result in a significant reduction in direct horizontal wave loads, and will lead certain reduction in wave-induced seepage overturn moment on the bottoms of a pair of circular cylinders. The variation of ocean wave condition and structure geometry condition may have some influence on wave-induced seepage loads, especially on seepage moment. In certain condition, wave-induced seepage loads may have same order of magnitude as the direct wave loads. Furthermore, compared with compact cylinders, the porosity of a pair of the circular cylinders may also lead more similarity of the variation of wave-induced seepage loads on two cylinders.

Key words: a pair of porous circular cylinders, wave diffraction, wave force, seabed, seepage uplift force, overturning moment