液状化を考慮した津波の戻り流れによる構造物周辺の洗掘メカニズム  [in Japanese] SCOURING MECHANISM AROUND STRUCTURE BY RETURN FLOW OF TSUNAMI CONSIDERING LIQUEFACTION  [in Japanese]

Access this Article

Search this Article

Author(s)

Abstract

東北地方太平洋沖地震津波により破堤した堤防周囲の局所洗掘は,その深さや拡がりが大きく復興において高い障害となった.波による水底侵食の要因はせん断力による土砂移動と液状化である.前者は多くの津波研究で考慮されているが,後者について定量的な評価は行われていない.本研究では洗掘メカニズムの解明を目的にせん断移動と液状化を組み込んだ数値モデルを開発し,大きな津波被害の生じた破堤箇所周辺に実際に適用した.その結果,戻り流れ時に水位が低下し,開口部の堤防端で液状化現象が発生し,せん断力による最大洗掘深と比較して28%の深さまで液状化することが示された.これにより,地盤条件によっては津波の洗掘計算を実施する際,液状化現象も考慮する必要があることが明らかとなった.

 The 2011 Tohoku Tsunami left many spots of deep and wide scouring near coastal structures such as levees, tidal gates, buildings, etc. The scouring caused major damage to the structures. There are two known scouring mechanisms; erosion by bottom shear stress and liquefaction by pore-pressure. The former is established; however, the latter has not been quantified. We advanced a quasi-3D numerical model by a finite volume method to simulate the flow and sediment transport. Temporal and spatial porepressure calculation under the ground was newly developed to find liquefaction. We applied the model to the breached spot of the coastal levee at Fujituka on the Sendai Bay Coast where the levees with gaps were assumed as the initial condition. We found the depth of liquefaction reached 28% of the maximum erosion depth by the bottom shear stress. We concluded that although erosion by the shear stress is the major process, liquefaction by the pore-pressure is also significant.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 71(2), I_241-I_246, 2015

    Japan Society of Civil Engineers

Codes

  • NII Article ID (NAID)
    130005109313
  • Text Lang
    JPN
  • ISSN
    1884-2399
  • NDL Article ID
    027077821
  • NDL Call No.
    YH267-236
  • Data Source
    NDL  J-STAGE 
Page Top