Experimental Investigation of the Coupling Effect of Jackup Offshore Platforms, Towers, and Seabed Foundations under Waves of Large Wave Height

Abstract

A large number of jackup offshore platforms with towers are widely applied in ocean engineering. The dynamic response of the platforms to waves of large wave height is critical, as such waves may cause platform accidents, property damage, and casualties. Therefore, it is important to investigate the coupling effect of jackup offshore platform, towers and seabed foundations under waves of large wave height. In this study, the coupling effect of offshore platforms, tower structures, and seabed foundations under the impact of waves of large wave height was studied via a physical flume model test. The experimental results show that the impact of waves of large wave height on the platforms is significant when the wave is blocked by the platform surface as the water body gathers under the platform surface, causing a pile group effect that results in the onshore piles being subjected to larger pressures than the front ones. The combined action of wave impact and pile leg squeezing force leads to an increase in the pore pressure of the foundation bed near the pile leg, and the soil near the pile leg becomes soft, revealing the mechanism of instability of the offshore platform’s pile foundation under waves of large wave height. The acceleration of the longitudinal movement of the platform increases under waves of large wave height, and the vortex-induced vibration of the platform includes the vibration along the direction of the wave and perpendicular to it. A coupled vibration effect between the tower structure and the platform occurs under waves of large wave height, reducing the vibration of the platform itself. Furthermore, damping members are installed on the tower structure, greatly reducing the natural vibration period and the motion response of the tower structure. This study provides significant enlightenment for the design of offshore platforms with towers to protect against waves of large wave height.