A Study on Estimation of Tsunami External Forces of Pontoon by The Mooring Pile System

Abstract

In this paper, responses of a pontoon in tsunami were studied. As an example, a pontoon by the mooring pile system of Izushima fishing port in Miyagi Pref. was treated. The pile of the pontoon was pulled out of the tsunami which was derived from the Great East Japan Earthquake. Model tests in a solitary wave was carried out and tsunami simulation was also carried out. The pontoon was capsized in fast elevating cases of water surface. In order to suppress the capsizing, it is effective to place the roller fender lower than the gravity center to increase restoring moment. According to the tsunami simulation for Izushima fishing port, tsunami height was small enough compared to the wave length and elevation speed was slow. Thus, the pullout force of the pile is estimated mainly from surplus buoyancy, and capsizing should not be occurred.