本研究的目的為量測高鐵列車通過路堤結構在不同的土層型式引致的地盤振動,利用Bornitz與Wiss衰減公式分析各土層型式的衰減係數,以便瞭解現地土層的衰減特性。並藉由資料統計分析,探討高速鐵路行駛於路堤結構上所引致的地盤振動之振源衰減型式及頻率影響等。 經由本研究分析可發現高鐵於路堤結構用Bornitz之線振源較點振源及中間振源為佳。另高鐵於路堤之衰減情形,分析結果顯示隨著地盤愈硬而衰減趨緩。將1/3倍頻中心頻率分成低(1~8 Hz)、中(10~25 Hz)、高頻(31.5~100 Hz) 3個頻率帶分別評估其衰減係數,分析結果顯示高頻段的衰減較能反應出各現地土層衰減情形,而中低頻段的衰減則無規律性,因此有必要將1/3倍頻中心頻率分段探討其衰減行為。 另外,本研究最後將使用5種不同預估方法,利用現地量測近距離(28 m)的振動資料推估遠距離(130 m及210 m)的振動並與實際量測值比較。本研究建議將1/3倍頻中心頻率分成低、中、高頻推估遠距離的振動大小較為簡便且精確度合宜,可供工程界計畫初期評估之用。
This research measured the ground vibrations of different soil types which caused by the high-speed trains on the embankment structures. Both Bornitz and Wiss methods were used to analyze the attenuation coefficient for each soil type. The proper source type and the effect of frequency factor are also studied in this research. These analyses show that the type of line-load vibration source presents better statistical results than other vibration source types for high-speed trains on embankment. The attenuation coefficient of ground vibration increases when ground becomes softer. Besides, the analyses show that the attenuation of high frequency can relatively reflect the attenuations of each soil type, however, the attenuation of low and middle frequencies are irregular if the 1/3 Octave Band Center Frequency is divided into three parts: low frequency (1 to 8 Hz), mid frequency (10 to 25 Hz), and high frequency (31.5 to 100 Hz). Therefore, it is really necessary to divide the 1/3 Octave Band Center Frequency into three parts for calculating the attenuation coefficients separately. Finally, this research compares the predicted ground vibration with measured results using five possible prediction methods. The results suggest that it is simple and reasonably accurate for the analysis using low, mid, and high frequencies for the 1/3 Octave Band Center Frequency. This can provide engineers to estimate the ground vibration in the future projects.
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