高速列車所引致之噪音和振動問題甚為重要，其在軟弱地盤所造成的長週期波微動現象向為工程界所關注。本研究係以簡易有效之分析取代有限元素法，討論列車作用下橋墩基礎和鄰近土層振動反應。研究將橋墩和土壤-基礎拆解成個別之子結構模擬，並考慮上部橋梁結構和下部基礎地盤之力平衡性，藉以納入基礎柔度影響;同時配合土層衰減律求取鄰近地盤振動反應，並使用1/3 八音階寬頻分析和主動控制理論了解不同車速行經所造成之地表振動量和減振效益。研究發現:改變上部橋梁結構質量與勁度和其振動特性，對鄰近地表之振動反應、影響甚微，若欲減少地表振動，仍應以改善基礎構造及地質特性等方式較為有效。 Noises and vibrations induced by high-speed-rail trains are important engineering issues. The micro ground vibrations of the long-period waves have received major attentions. This study presents a simplified but effective analysis for the train-induced vibrations of a bridge-pier-foundation and the near-by ground. While the superstructure is decomposed into a three DOF system, the under-ground foundation is modeled by a number of discrete elements using the wave equation analysis. Compatibility condition of the transmitting force between the superstructure and the foundation is satisfied, which provides the foundation flexibility to the analysis. The attenuation laws for waves propagating along the ground surface and 1/3 octave band spectrum are both adopted for the discussions. Effect of the foundation flexibility is discussed in order to conduct the active control analysis for the superstructure. This study found that improve the quality, stiffness and change the vibration characteristic of superstructure, could not influence the vibration reacts. The train-induced ground vibrations would be more pronounced at relatively high speeds, modifying the under-ground structure and improving the geological characteristic of the soils could more effectively reduce the ground vibrations.