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Title: 應用HHT 分析波引致海床液化之生成與消散機制---波群效應(II)
Application of HHT to Analysis on Mechanism of Generation and Dissipation of Wave-Induced Seabed Fluidization---Effects of Groupiness(II)
Authors: 臧效義;歐善惠
Contributors: NTOU:Department of Harbor and River Engineering
Keywords: 海床液化;生成機制;HHT;群性
bed fluidization;mechanism of generation;HHT;wave groupiness
Date: 2008-08
Issue Date: 2011-06-29T01:38:50Z
Publisher: 行政院國家科學委員會
Abstract: 摘要:近岸海域地區波浪與底床交互作用明顯,且非線性和群性在工程上為重要的波浪 特性。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 浪能量減衰以及近底床處波浪與液化海床交互作用的結果;且不同波浪特性引致的孔 隙水壓抬升行為亦不同。應用具有可分析非線性、非穩態及可呈現瞬時頻率與能量分 佈的HHT,從本年度第一年核准計畫之初步結果顯示,振動和超額孔隙水壓可從 IMFs 重組而得,且在孔隙水壓抬升過程中會有倍頻成份的產生。本年度計畫擬針對 不規則波群引致的海床液化反應,藉由 HHT 分析不同群性造波條件之試驗資料, 深入探討群性的影響,並與第一年之結果完整論述液化反應的生成機制。
abstract:In nearshore waters, wave-seabed interactions become dramatically intense. Wave characteristics of nonlinearity and groupiness are very important on coastal engineering. Results from a series of lab flume tests in past years have illustrated that variations of pore pressure building-up imply 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 and near-bed wave-fluidized seabed interactions. The behaviors of pore pressure building-up might change due to different wave characteristics. Hilbert-Huang transformation (HHT) is proved to be applicable to nonlinear and non-stationary processes; its final presentation of the results is an time-frequency-energy distribution. Preliminary results from granted fist-year investigations illustrate that oscillating and excess pore pressures can be extracted by reconstruction of the IMFs of pore pressure. Superharmonic components were generated during excess pore pressure build-up. Thus, present study is aimed at detailing the interaction responses induced by irregular wave groups and fluidized bed soils. By analyzing pore pressure data with different wave groups with HHT, the effects of groupiness shall be investigated and the results of first-year study shall also be adopted to describe the mechanism of generation of wave-induced seabed fluidization.
Relation: NSC97-2221-E019-042
Appears in Collections:[Department of Harbor and River Engineering] Research Reports

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