鐵道橋樑基礎型式主要包括路堤和樁基，其中樁基礎在土壤液化和地盤流動影響下的反應為近年所廣泛探討的工程課題。本文將以簡易之動力分析模式EQWEAP 處理該項問題，模式係將集中質塊分析所得之自由場地盤反應作用於樁基，並使用波動方程分析求取樁體變形和內力，該項分析方法經與有限元素分析比較證實可行。為模擬液化影響，本文建議以液化潛能評估法分析之土質折減條數用於土壤彈簧，以弱化液化區的土壤支承力; 另可藉擬動態土壓模擬地盤流動(側潰)影響。透過相關案例分析，研究發現樁頂將產生最大位移量，近樁頂部位之剪力亦大，彎矩則取決於樁頂束制性，若屬剛性束制，則最大彎矩仍將發生於樁頂; 在液化層與非液化層之介面處，樁身變形和內力均有明顯驟增現象，相關部位俱可能產生斷樁。相關分析應以個案方式討論，吾人可藉地盤改良避免液化，並強化基礎結構以避免地盤流動影響。 Foundations for railway mainly include embankment and piles. The problems encountered in pile design regarding the soil liquefaction and later spread induced by the earthquake have been extensively studied in recent years. This paper suggests a simplified procedure EQWEAP for dynamic analysis of this task. Free-field ground motions obtained from the lumped mass analysis were applied to the wave equation analysis to achieve the pile response. The solutions were verified with the FEM analysis. For liquefaction simulations, soil parameter reduction factors from the liquefaction potential analysis were used for the soil springs along the pile. On the other hand, dynamic earth pressures induced by the lateral spread of the ground could be implemented into the pile analysis monitoring pile response. Based on the case studies, it is found that the maximum displacements would occur at the pile head, and the maximum shear would occur nearly at the pile head. Bending moments are highly dependent of the pile head boundary conditions. For rigid pile-cap connections, the maximum moment would appear at the head too. At the interfaces of the liquefied and the non-liquefied layers, sharp changes of the displacements and the internal forces were seen. All these locations could yield to failure. One may minimize the site liquefaction potential by soil stabilization or strengthen the pile foundation to avoid the lateral spread influences.