自1964年日本新瀉大地震及美國阿拉斯加大地震相繼發生土壤液化現象以來，經歷數十年研究，土壤液化之成因已漸為人了解，土壤液化之防治工法亦不斷被研究開發，其中礫石樁工法已被證明具有相當不錯之液化防止效益，為海埔新生地地盤改良，防止地震時土壤液化常見的施工方法；關於地震時礫石樁與四周地盤之互制行為與礫石樁之排水效應如何，是設計礫石樁前必須瞭解之基本資料，本研究是利用三維非線性之有限元素分析程式進行地震時地盤之孔隙水壓、有效應力、地盤變位等之研究分析，希望能由分析結果一方面證實程式之實用性，另一方面了解礫石樁之滲透性、樁徑、樁距等參數對土壤液化之影響程度以為礫石樁設計之參考依據。 本研究利用以 Biot 多孔介質變形理論為基礎所發展出來的非線性有效應力之三維有限元素分析程式，進行細粒土壤及地盤受震之反應分析，其中土壤及礫石樁是以8節點塊狀元素模擬並分別給予不同的土壤性質，元素的非線性行為採用帽蓋模式來模擬，孔隙水壓模式則使用Pacheco配合帽蓋模式所提出的孔隙水壓模擬方法進行模擬。 由研究的結果發現，於較大地震作用下，細粒砂質土壤之滲透排水性不佳時極易造成土壤液化，當這類土壤中打設礫石排水樁後確實會降低土壤液化之潛能，當打設之礫石樁愈密、樁俓愈大、礫石之滲透性係數愈大，則土壤受震液化之可能性亦隨之降低。 From 1964 Japan Niigata earthquake and America Alaska earthquake that badly damaged structures ,Expert and scholar first noticed that the fine sand soil will cause liquefaction under strong earthquake. After about 30 year experience accumulated it had been proved that the gravel drain column is a economic and effective way to prevent fine sand to Liquefaction. In this paper a nonlinear 3-D effective stress finite element model is developed to analysis the seismic response of gravel drain column .In this model the 8-node brick element are adopt to model the reclaimed land soil and the gravel drain column , but with different material property respectively. In the analysis, the cap model and it associate pore water pressure model are employed to simulate the nonlinear soil behavior and pore water pressure build up. From the analysis , it can observed that the gravel drain column is effective for decrease the build up pore water pressure of reclaimed land soil under seismic to prevent soil liquefaction . The diameter of gravel drain column and distance between two gravel drain column influenced the efficiency of decrease build up pore water pressure , If we can get and realize the medium properties of gravel used in the gravel drain column .
