橋梁部に堆積した杉流木に関する水理模型実験  [in Japanese] EXPERIMENTAL STUDY ON ACCUMULATION OF CEDAR AT THE BRIDGE  [in Japanese]

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Abstract

<p> 大雨によって河川に流出した流木による被害が全国でみられる.一例として,2016年の岩手県豪雨災害における小本川の氾濫がある.一方,2017年7月に秋田県の雄物川にて発生した洪水では,橋梁や農地への流木の堆積が確認され,堆積した流木は針葉樹の杉であった.流木の流出過程を知ることは重要であるため,本研究では実在する橋梁をモデルとし,杉を用いた水理模型実験を行った.実験では,橋梁への流木の堆積数と橋梁の上流側と下流側の水位の変化に着目した.その際比較対象として流木の長さ,混合流木の平均長さ,流量などに関して複数のパターンを用意し結果をまとめた.実験より,流木長が長いほど橋梁への堆積が多いことが判明したが,水位は流木長に関わらず一定であった.</p>

<p> This paper presents an experimental approach to investigate the accumulation process of cedar at the bridge. Recently, it is frequently confirmed damage resulting from driftwoods in Japan. For example, Typhoon No. 10 in August 2016 caused flooding of Omoto River. It was a possibility of similar disaster in Akita Prefecture which has a lot of cedars. The hydraulic model experiments were carried out using a bridge model at Omoto River. The scale was 1/180. It based on the width of Omoto River and the water channel. The cedar rod was used for driftwood model. In the experiment, we focused on the number of driftwood accumulation at the bridge and changed in the water level on the upstream and downstream sides of the bridge. At that time, several patterns were prepared regarding the length of the driftwood, the average length of the mixed driftwood, and the flow rate as comparison objects. In conclusion, the experiment shows that the longer the driftwood length the larger the amount accumulation at bridge. This tendency was also observed in the mixed driftwood experiment. However the length of driftwood were different, water level was not changed. And the time which was taken to stop the rise of water level did not change due to the difference of driftwood length. In the experiment of the flow late, the ratio of driftwood accumulation was increased with the increase of the flow rate. In addition, it was suggested that flow velocity related to driftwood accumulation.</p>

Journal

  • Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research)

    Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research) 75(5), I_255-I_260, 2019

    Japan Society of Civil Engineers

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