台灣地震發生頻繁，地震期間地盤可能發生土壤液化現象，將導致建築物、橋梁與風機結構等基礎瞬間失去垂直與水平向之承載能力。依據現行設計規範為將具液化潛能之地盤參數進行不同程度之折減作為設計，而各規範建議之折減係數範圍差異甚大，且該設計觀念為將複雜之土壤液化行為簡化為擬靜態分析之設計方法，並未考慮液化土壤結構受震互制之複雜行為。因此，本研究利用離心模型試驗與FLAC2D二維有限差分數值模型分析，進行一系列之液化地盤-樁基礎-上部結構之受震互制試驗與模擬分析，探討土壤液化對樁基礎結構物各項設計考量因素之影響。並利用動態受震與擬靜態側推分析之結果，提出一套等值液化參數折減係數DE’之評估流程，針對現行規範建議之液化折減係數提出定性與定量之討論。 本研究建立之數值模型經由參數率定後，方可有效模擬離心模型試驗之樁土受震液化反應。在考量等效單樁、群樁、液化、非液化、長短結構週期與多組人造震動等眾多因素下之分析結果顯示，在相同慣性力作用下，動態分析求得之樁身變位與彎矩反應均較擬靜態分析結果大。而12組震動事件之分析統計結果顯示，土壤液化對結構慣性力實具減震之作用，並對樁身變位、旋轉角與彎矩等反應均有負面之影響，而對樁身最大剪力分佈則無明顯影響。針對短週期結構模型之液化折減係數DE研究結果顯示，日本道路協會(JRA)建議之DE在多個案例分析中發生不保守之狀況；而日本建築學會(AIJ)建議之DE則多為保守之情形。最後，藉由不同等值條件求得之平均等值液化折減係數DE’界於兩規範建議值之間。綜整上述結論以供未來相關研究與工程實務設計參考。 ;Taiwan is a seismic active zone. Soil liquefaction often occurs during strong earthquake. It will greatly reduce the horizontal and vertical bearing capacities of foundations and cause unacceptable deformations of structures. The current design codes use the reduction coefficient DE to reduce the soil’s modulus and strength so that the softening effect caused by liquefaction can be taken into account in the traditional quasi-static design methodology. This methodology is unable to consider the complicated seismic liquefied soil-structure interaction (LSSI). This study aims to establish a simple and practical numerical model to investigate LSSI effect of pile structures. The FLAC2D software was used to create the model. The PM4Sand constitutive law was used to simulate the stress-strain-pore pressure relations of soils. At the first, the parameters of PM4Sand model was calibrated by the results of dynamic centrifuge tests. It is found that the test responses of LSSI can be reasonably simulated by the numerical model. After that, a series of LSSI numerical tests were performed by the proposed model considering the differences of equivalent single pile and group piles, liquefaction and non-liquefaction, short and long period structures, and input earthquake motions. The test results show that the deformation and bending moment of pile obtained from dynamic LSSI analysis are larger than those from static pushover analysis under the same inertial force of upper structure. Based on the statistical results from twelve different input motions, soil liquefaction reduces the inertial force of superstructure and increases the deformation, rotation and bending moment of piles. The statistical results of numerical analysis were used to calibrate the equivalent reduction coefficient DE’ used in quasi static analysis. The calibrated average DE’ is about 0.25 which less than DE=0.33 suggested by Japanese Road Association and greater than DE=0 suggested by Japanese Architectural Institute for the numerical case in this study.
