報告書番号

U99011

タイトル（和文）

人工島防波護岸の耐震性に関する研究（その５） --実規模防波護岸の地震時変形と機能維持検討--

タイトル（英文）

Study on Seismic Stability of Seawall in Man-made Island (Part5)-Deformation of Actual Seawall during Earthquake and Estimation of Seismic Performance-

概要 （図表や脚注は「報告書全文」に掲載しております）

地震によって変形を生じた人工島式原子力発電所防波護岸の地震後の越波防止機能を検討するため，遠心模型実験結果，ならびにケーソン護岸の地震観測による知見を考慮した実規模防波護岸の地震時変形に関する数値解析より，防波護岸が基準地震動S2クラスの地震を受けた場合の変形量を予測した。また，地震によって変形を生じた消波工が越波量に及ぼす影響を調べるため水理実験を実施した。その結果，(1)地震による消波工法面の緩勾配化，天端高の減少は，越波量の増大につながらない(2)実規模防波護岸が基準地震動S2クラスの地震を受けた時のパラペット天端の沈下量，水平変位量は，海底砂層厚が10mで相対密度60%程度と比較的緩い場合でも，それぞれ0.12m～0.2m，0.18m～0.6m程度であることがわかった。これらの結果より，地震によって変形を生じた防波護岸は，地震後の越波防止機能を十分維持していることを示した。

概要 （英文）

In the development of the man-made island siting technology of nuclear power plants,assessing the stability of the seawall against large ocean waves and earthquakes is indispensable. Concerning the seismic stability of the seawall,prediction of the deformation of the seawall during earthquake is important to evaluate the seismic performance of the seawall after the earthquake. In this report,the deformation of the actual seawall was predicted from the results of the centrifuge model tests and the case studies by the numerical analyses.Furthermore, wave flume model tests of the seawall with the deformed armour embankment by the earthquake shaking were conducted to investigate the effects of the deformation of the armoured embankment to the overtopping discharge by the waves. Obtained results were as follows:(1)It was experimentally confirmed that the slope gentleness and the decrease of the top elevation of the armoured embankment induced by the earthquake did not lead to the increase of the overtopping discgarge by the waves after the earthquake. (2)Subsidence and lateral displacement at the top of the parapet of the seawall caused by the S2 scale earthquake were approximately 0.12m～0.2m and 0.18m～0.6m respectively under the condition that the thickness of the sand seabed was 10m and relative density was 60%. (3)Even though such displacements were induced at the top of the parapet of the seawall, seismic performance of the seawall against the large waves was kept after the earthquake.

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