以連續小波轉換分析土層表面波波速之研究

A Study on the Wave Velocity of Rayleigh Wave Using Continuous Wavelet Transform

王裕賢(Yu-Hsien Wang)

指導教授 ： 蔡佩勳

朝陽科技大學/理工學院/營建工程系/碩士(2010年)

摘要

傳統的表面波譜法(SASW)是利用快速傅立業轉換將時域訊號轉換至頻率域後再進行相位譜分析，但相位譜容易受到雜訊干擾造成跳動頻繁，進而限制分析結果之準確性。本研究將以一種時頻分析方法以求解表面波之波速，利用表面波攜帶能量大於實體波之特性，利用連續小波轉換將時域訊號轉換至時頻域訊號，由對應於某頻率下不同收波器所接收能量較高的表面波之傳遞時間來計算其波速，進而求出表面波之頻散曲線。本研究將分別以單一土層、雙層土層以及三層土層進行討論。從分析的結果顯示，本研究發展的方法可以推估土層之厚度及各土層之波速，為了驗證其可行性，本研究最後也以現地試驗來驗證。

關鍵字

連續小波轉換 ； 表面波 ； 頻散曲線

並列摘要

Conventional SASW method is used fast Fourier transform to convert time domain signals to frequency domain. Then the frequency-dependent phase angle can be obtained from phase spectrum analysis. But it can be interfered with surrounding noise. This research will develop a time-frequency method to evaluate the velocity of surface wave. The method is used continuous wavelet transform to convert time domain signals to time-frequency domain signal. The velocity of surface wave will be determined from the incoming time of higher energy wave and the distance of two receivers. Because the signal has characteristics of time and frequency domain, the velocity can be expressed a function of frequency. Therefore, the dispersion curve will be evaluated from the analysis. The dispersion curves of a single layer soil, two layers soil and three layers soil are analyzed by the time-frequency meted. For practical application, a experimental test was performed to verify the rationality of the proposed method. From the results of numerical analysis and experiment test, it cam be concluded that the proposed method can evaluate the velocity of surface wave.

並列關鍵字

Continuous Wavelet Transform ； Rayleigh Wave ； Dispersion Curve

參考文獻

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