土體表面含凹槽(或填充凹槽)對暫態波傳行為之探究

本研究於試驗模型中設置小型凹槽(或填充凹槽)以探究地表不規則區域對於暫態擾動源作用在土體表面產生的寬頻振動傳遞之行為。試驗利用敲擊鎚敲擊土體表面做為擾動源以產生暫態波傳，並透過加速規量測土體表面之加速度訊號，試驗之研究參數為凹槽之深度和凹槽之填充物，量測結果透過地表速度振幅降低比 Ar和三分之一倍頻程頻譜進行分析，並探討凹槽深度和填充物對於阻隔寬頻振動之貢獻。試驗結果顯示，增加凹槽深度能有效降低主要阻隔頻段之振動傳遞，且有效阻隔頻段之占比也會隨著深度增加而提升；此外，凹槽內含填充物會改變試驗模型之均勻性，導致試驗試體的密度產生不同程度的改變，進而影響有效阻隔頻率。本研究使用的四種填充物在主要阻隔頻段之阻隔效率依序為: 開口凹槽、合成橡膠、聚苯乙烯泡沫板和聚氨酯發泡材料。

關鍵字

暫態波傳；凹槽；填充凹槽；振幅降低比；頻譜分析

並列摘要

In this research, small trenches (or in-filled trenches) are set in the experiment model to explore the behavior of the surface irregularity region for the transmission of broadband vibration generated by the transient disturbance source on the soil surface. The experiment uses a percussion hammer to hit the soil surface as a disturbance source to generate transient fluctuations, and the acceleration signal of the soil surface is measured through an accelerometer. The research parameters of the experiment are the depth of the trench and the filling of the trench. The results are analyzed through the table velocity amplitude reduction factor Ar and one-third octave band rms amplitude spectrum, and the contribution of trench depth and filling to the isolation of broadband vibration is discussed. The experiment results show that increasing the depth of the trench can effectively reduce the vibration transmission of the main reducing frequency band, and the proportion of the effective reducing frequency will increase as the depth increases; in addition, the filling in the trench will change the uniformity of the experiment model, as a result, the density of the experiment specimens changes to varying degrees, which in turn affects the effective reducing frequency. The reducing efficiencies of the four fillers used in this study in the main reducing frequencies are: open trenches, synthetic rubber, polystyrene foam board, and polyurethane foam.