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Application of Hht to Analysis on Mechanism of Generation and Dissipation of Wave-Induced Seabed Fluidization--- Dissipation Mechanism(III)
|Contributors: ||NTOU:Department of Harbor and River Engineering|
fluidization;dissipation mechanism;wave decay;interaction;HHT;EEMD
|Issue Date: ||2011-06-29T01:38:55Z
|Abstract: ||摘要:從第一年和第二年計畫的成果得知，當海床發生液化反應會讓水 表面波浪產生減衰，而且波浪減衰率與非線性強度大小指標耳索數(Ur) 成正比關係。因此，波浪之減衰與海床產生液化反應有明顯關聯。另 外，從過去波引致底床液化反應的水槽試驗結果得知，孔隙水壓的抬 升變化過程隱含液化反應的生成機制，而在液化後其變化不僅反應液 化海床的消散機制，也關係波浪能量減衰變化以及近底床處波浪與液 化海床交互作用的結果。由於不同波浪特性引致之不同的孔隙水壓抬 升與消散大都為非線性及非穩態，因而以可呈現瞬時頻率與能量分佈 的HHT 進行分析是最佳選擇。本年度計畫擬應用第二年計畫正建置的 EEMD 技術，針對孔隙水壓消散和波浪與液化海床交互作用之相關物 理現象進行分析討論，並與前兩年之結果整合以期能完整論述液化反 應的生成和消散機制。|
abstract:Preliminary results from granted 1st and 2nd- year investigations illustrate that wave decay significantly occurs in a fluidized seabed and its ratio is directly proportional to the magnitude of Ursell number (Ur). Thus, the wave decay is closely associated with the fluidized response in the seabed. Past results of a series of lab flume tests have further illustrated that pore pressure variations during the stage of increasing excess pore pressure consist of the mechanism of generation of fluidization. Moreover, pore pressure variations in post-fluidization not only reveal the mechanism of dissipation of fluidization but also relate wave decaying with wave-fluidized seabed interactions. Since behaviors of pore pressure building-up are diversified due to different wave characteristics, Hilbert-Huang transformation (HHT) scheme is preferably applied to deal with the nonlinear and non-stationary measurements for deriving the time-frequency-energy distributions for analysis. Thus, present study is aimed at investigating the dissipation of pore pressure and the wave-fluidized seabed interactions in a fluidization test by the EEMD scheme established in the currently granted 2nd-year project. In the end, the results of previously granted studies shall also be combined to summarize the mechanism of generation and dissipation of wave-induced seabed fluidization.
|Appears in Collections:||[河海工程學系] 研究計畫|
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