為了解近液化底床處傳輸的特性，本試驗應用超音波Doppler流速計量測底床上方 1cm 處之流速，配合底床上方等間距水深 5 支光學式濃度計量取懸浮漂砂濃度剖面，和底床內部不同深度孔隙水壓反應土壤內部反應﹔試驗波浪條件以規則波、規則波群和具不同群性的不規則波浪進行試驗。由規則波和規則波群試驗結果顯示在非液化反應時，近砂質底床處水平方向流速可以線性波理論描述，其與理論值之比在 0.91~1.14 的範圍內，而垂直方向流速與理論值比在1.03~1.30 範圍內。起始液化反應時，水平方向流速會隨平均孔隙水壓抬升而變小，垂直方向流速則隨孔隙水壓抬升而變大，且不受起始液化層厚度影響，垂直方向流速放大的倍數均是整回合液化試次中最大者。隨液化次數增加，水平和垂直流速縮小和放大的量也會慢慢減少，最後回復非液化反應。當發生液化反應時，垂直方向流速產生振幅放大現象之後，於近底床處會有大量的懸浮漂砂濃度的抬升，且濃度剖面為冪次型態的分佈。具不同群性之不規則波浪試驗結果顯示，海床液化時平均孔隙水壓多階段抬升的過程與波浪群性有關，愈大的 GF 值，其使海床產生起始液化所需有義波高愈小。

In this thesis, a three-component acoustic Doppler velocimeter was adopted to measure the velocity field at 1cm above the seabed. Depth profiles of sediment concentration with 5 optical probes above and pore pressures with 5 transducers inside the seedbed are together used to investigate the features of suspended sediment transport near a wave-fluidized seabed. Regular waves, wave groups and irregular wave of different groupiness were generated in the laboratory flume tests. As a result, in unfluidized responses the measured near-bed velocities can be well predicted by linear theory under regular waves and wave groups. The ratios of measured to predicted were between 0.91 and 1.14 for horizontal velocity, while those were between 1.03 and 1.30 for vertical velocity. However, in fluidized responses a decrease in the horizontal velocity and an increase in the vertical velocity closely correlate with mean pore pressure build-ups. Regardless of the thickness of fluidized soil layers, maximum amplitude amplification in vertical velocity occur in the initially fluidized responses. After several wave-induced soil fluidization, the horizontal velocity amplitude reductions and the vertical velocity amplitude amplifications gradually decreased, become as the unfluidized response. During the fluidization, the suspended sediment concentration increases significantly after the vertical velocity amplitude amplification, while its depth profiles approximate a power law. Experimental results under irregular waves with different groupiness show that stepped build-ups of mean pore pressure closely relate with wave groupiness(GF). The larger values of GF the smaller significant wave height was needed in the initially fluidized responses.

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