ABSTRACT

To apply a steel caisson with skirt, which takes suction effect into the stability, to the coastal structure on soft seabed, dynamic response of the caisson structure with suction and its soft foundation under wave attack was simulated by an advanced caisson structure seabed interaction analysis. Dynamic response of a caisson structure with suction and seabed around it was 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.

INTRODUCTION

The offshore structure foundation plays a very important role for the stability of offshore structures installed in a great water depth. Judging from the fact that the reclamation works recently have developed from seacoast to offshore, the installation water depth of offshore structure becomes larger, and also it is not so easy to sufficiently secure the supporting force of seabed ground for the installation of offshore structure as before. While severe sea conditions on site require the construction schedule to be shorten and easy. As described above, the construction of maritime structures has been developed from sites on rigid bed such as rock-base or sand layer in a shallow water to those on soft bed in a deep water. The demands mentioned above motivate to apply the suction effect to stabilize offshore structures, and actually it has been applied in the North Sea (Tsuzuki et al., 1995). In practice, the suction is effective not only for the increase of the penetration force in the installation of an offshore structure but also for the resistance to a pull-out force due to the interruption of atmospheric pressure after installation.

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