臺灣位於歐亞板塊交界，地震頻繁，而臺灣西部平原區，均屬於地質鬆軟的新沖積地層，地下水位亦高，在大地震發生時，極有可能發生土壤液化現象。在過去有許多地震事件造成砂土層液化，導致樁基礎遭受斷樁的災損案例，此種災損不容易修復及發現，因此土壤液化時樁基礎的受震行為，成為重要的研究課題。 本研究利用離心振動台輸入不同振幅的水平振動，引致試驗砂床發生不同程度的液化。在發生不同液化程度下，本試驗設計一個施加水平力的氣壓系統，可以在砂土層因水平振動引致砂土液化，振動停止後，在超額孔隙水壓尚未消散或部分消散時，隨即快速進行水平推樁的動作。利用模型計測彎矩樁所量測之彎矩沿深度的分佈，經由溫克樑理論，嘗試了解及建立埋置於不同液化程度土層內的樁基礎的非線性p-y曲線的形狀、強度與周圍砂層超額孔隙水壓的關係。 試驗以80倍黏滯性液體作為飽和流體，在80g離心重力場下模擬相對密度60%、厚度25.6m之砂質地盤液化樁土間動態行為。進行液化地盤水平推樁試驗共22組，取出其中5組試驗成功且分析結果完善，試驗間有足夠差異性來進行比較及討論，試驗結果顯示： (1) 未液化或部分液化最大彎矩約發生於樁深4 m處(約4 D，D為樁直徑)，而液化土層則最大彎矩約發生於樁深9 m處(約9 D) (2) 液化後之殘餘土壤側向反力係數 kh約為未液化土壤側向反力係數 kh之百分之一 (3) 將各試驗不同水平荷載下與樁頭水平變位和p-y曲線回歸出y=ax/(b+x)方程式，將其中的參數a和b對應到各試驗的地表ru值，再用方程式擬合，得到不同ru值對應a、b參數方程式，代入不同ru可以得到地表水平變位與樁頭水平荷載關係和p-y曲線。 ;Taiwan is situated on the borderline of Eurasian plate with a great amount of earthquakes. The plain of the western Taiwan is categorized as new alluvial layer with soft soil and high water table. It is possible to result in soil liquefaction. There are many sandy soil liquefaction during earthquakes in the past, and it led to the failure of pile foundation, which is not easily discovered and repaired. The behavior of pile foundation in liquefiable soil under shaking is one of the unneglectable topics. This research utilizes the centrifuge shaking table with different amplitudes of horizontal vibration, which leads to a variety of liquefaction of experiment sand bed. Under different kinds of liquefaction, this experiment set up a serve pneumatic air cylinder providing horizontal force, which conducts the fast lateral loading test during excess pore water pressure yet or partially dissipated immediately after shaking. The moment distribution along the depth of the pile were measured with strain gauges. Construct the model of the non-linear p-y curve shape, strength, and relationship between excess pore water pressures of the pile in the different kinds of liquefaction. The experiment is focused on pile-soil dynamic interaction of sandy ground with 80 times viscous fluid as the saturated fluid under 80g centrifuge gravity for simulating the sand bed with a relative density of 60%, and a thickness of 25.6 m. Totally conduct 22 sets of tests of the model pile subjected to lateral loading in liquefiable ground. Select the fittest 5 sets to operate analysis, which provides enough variance to compare and discuss. The result shows: (1) yet liquefied or partially liquefied maximum moment occurs at the pile depth of 9m (around 9 D); (2) the liquefied residual soil lateral reaction coefficient, kh, which is approximately 1% of non-liquefied soil lateral reaction coefficient. (3) Regress the relationship between horizontal loading and pile head horizontal displacement and p-y curve with the formula of y=ax/(b+x) from a variety of experiments, and attain different ru values corresponding to the formula with parameters a, and b.
