報告書番号

U03052

タイトル（和文）

段波津波による漂流物の衝突力に関する実験的研究

タイトル（英文）

Experimental sutudy on impulsive force due to collision of drifted body by borelike tsunami

概要 （図表や脚注は「報告書全文」に掲載しております）

津波漂流物の衝突力評価の第１段階として、漂流物を剛体とみなし、防波提や陸上構造物に衝突する場合を想定して、貯水部のゲート開放により段波津波を発生させた実験を行った。段波波力、各種形状剛体漂流物（横向きと縦向き配置の円柱と角柱、球）の運動と衝突力との関係、衝突時の質量係数等を検討した。砕波しながら衝突する段波の波圧は静水面付近で最大となり従来の非砕波段波圧算定式を上回る。実験に基づき、新たな波圧算定式を提案した。つぎに、水面に浮かんだ漂流物が衝突する場合、衝突直前の漂流物の運動量が同じならば形状によらずほぼ同じ衝突力を示す。一方、遡上段波による陸上漂流物が衝突する場合、漂流物と一体となって移動する周辺流体の質量や衝突力は漂流物の形状や運動特性の違いにより異なる。質量係数を取り込み各種形状漂流物に適用できる衝突力算定式を提案した。これより、未知であった漂流物の衝突力の概略が把握できる。

概要 （英文）

As the first step for estimation of impulsive force due to collision of drift body and tsunami, using bore like tsunamis generated by opening the gate of a water tank, physical model tests have been performed on collision of drift rigid body and tsunami with coastal and land structures. Bore like tsunami force, relationship between the rigid motion of drift body of several kind shapes (in the in-line and transverse collisions of cylinder and square column, and collision of sphere) and impulsive force, and the mass coefficient of drift body in collision with structures, are elucidated experimentally. As a result, it is firstly found that the wave pressure of bore like tsunami attacking with breaking indicates the maximum near still water level, and it overestimates that estimated by the usual wave pressure formulae of tsunami without breaking. So, a new wave pressure formula is proposed based on these experiments. Next, it is also found that in collision of drift body floating on the water surface, almost similar impulsive force occurs between drift bodies of the above kind shapes attacking with same momentums. On the other hand, it is found that in collision of land drift body due to tsunami running up to land, the mass of fluid moving and surrounding drift body, impulsive force on the land structure, and drift body motion are different between drift bodies of the above kind shapes. So, introducing the mass coefficient obtained by these experiments, a new formula of impulsive force of drift body is proposed for effective application to drift body of the above kind shapes. And thus, using the above formula, impulsive force of drift body, which was unknown so far, can be approximately estimated.

報告者

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