報告書番号

U00026

タイトル（和文）

無ひずみ模型実験による浮揚式発電所係留浮体の津波来襲時３次元挙動解明

タイトル（英文）

Three Dimensional Dynamic Behavior of Moored Floating Structure of a Nuclear Power Plant due to Tsunami Based on Non-Distorted Model Tests

概要 （図表や脚注は「報告書全文」に掲載しております）

日本海中部地震津波の際には，遠浅地形の長く続く海岸で，周期10分程度の津波本体の上に周期10秒程度のソリトン分裂波が複数重畳して津波の最高水位が増大した．このソリトン分裂波の周期と船体運動の固有周期とが近いため，航行中の漁船や防波堤・護岸を建設中の各種作業台船が共振運動により激しく揺れた．海上立地浮揚式発電所に対しても立地点によっては同様のことが懸念され検討が必要である．また，浮揚式発電所を囲む外郭防波堤の津波に対する遮蔽効果を調べておく必要がある．そこで，本研究では，大型造波水路津波発生システムを用いた縮尺1/150の無ひずみ模型により，沖合い津波を押し波あるいは引き波初動の正弦波やマグニチュード8クラスの断層運動により想定される津波で模擬し実験した。そして、ソリトン分裂津波による110万kw級プラント搭載係留浮体の３次元動揺特性および種々の開口率の港口部を有する防波堤に囲まれた同係留浮体の動揺特性を明かにした．

概要 （英文）

In the Nihonkai-Chubu Earthquake Tsunami (1983), tsunamis grew up into violent bores with shoaling and generated significant soliton fission waves on several coasts of wide continental shelf. Moreover, the split soliton waves induced the large motion of fishing boats, several kinds of deck barges and floating cranes, with which the breakwaters and the seawall caisson were being constructed at the Noshiro Port. Because, the period of the soliton waves is almost 10s and it is very near to the natural period of the ship motion. So, it was guessed that soliton waves induced resonant motion of the ships. The above resonant motion due to soliton waves may occur for the Floating type Nuclear Power Plant (FNP) if the FNP will be settled in the sea area with wide continental shelf and investigation is needed for this problem. Moreover,it is also necessary to investigate sheltering work of the breakwaters surrounding the FNP against tsunamis. In this paper, using the CRIEPI large wave flume, the non-distorted tsunami model tests were performed in the 1/150 scale model. Dynamic behavior was compared among motion of moored floating structure of the FNP due to sine wave tsunami with runup start and backrush start, and due to tsunamis caused by submarine earthquake using the fault model of the moment magnitude:Mw=8. First, the resonant motion of a moored floating structure caused by tsunami with significant soliton fission in the open seas without breakwaters was elucidated experimentally. Next, the dynamic behavior of the moored floating structure in a semi-closed basin surrounded by breakwaters with the opening due to tsunami was investigated. The several opening rates were applied in this model test. Relationship among the opening width of breakwaters, inflow velocity and water surface elevation in the mooring basin and 3-D motion of the moored floating structure were elucidated experimentally.

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