地震造成地盤液化時，位於側向滑移地盤的沉箱式碼頭及後線，向港渠移出，造成長時間碼頭作業停頓，造成極大的經濟損失。因此了解影響沉箱碼頭滑移的機制，並進行耐震設計；另外針對既存危險沉箱碼頭的可能復建補強對策，進行離心模型震動台試驗，藉以了解不同改善對策的有效性是有其必要的。本研究計畫預計執行三年。第一年模擬自由場飽和砂土液化的離心模型試驗。發展CPT及彎曲元件系統，量測模型地盤的動態性質。利用完整的量測計畫，了解液化過程中砂土變形機制及建立砂土勁度和強度的衰減模式；第二年針對位於側向滑移地盤的沉箱式碼頭，利用離心碼頭模型震動台試驗，探討碼頭的震動模態，同時考慮水平滑移模態及旋轉模態，了解影響沉箱碼頭向海側滑移的機制，並提出性能設計的分析方法；第三年則依據試驗得到的破壞機制，提出可能的復建補強對策，並進行離心模型震動台試驗，藉以了解不同改善對策的有效性及其評估方法。本研究計畫預期可以建立砂土受震時勁度和強度的衰減模式和了解砂土受剪膨脹效應，對砂土液化及量測加速度歷時的影響。建立不同超額孔隙水壓下所得到之不同剪力波速剖面，可以掌握Gmax的變化情形。了解在不同試驗條件下，沉箱周圍及背填土的孔隙水壓分佈情況及液化鋒面的發展情形及對沉箱水平變位量及傾斜角的影響。依據背填土不同的液化程度，提出合理估計地震時的動態土壓力及動態水壓力的方法，考慮旋轉及水平運動模態的相位差，建立評估沉箱碼頭水平外移量及傾斜量的計算方法。最後利用模型試驗的結果，評估不同復舊改善對策的有效性及建立可行的評估方法。The lateral deformation and surface settlement in the backfill behind the caisson-type quay wall induced by the lateral spreading during earthquakes may destroy the harbor facilities and result in the shutdown of harbor operations for a long period of time. This type of disaster would cause huge economic loss. Hence predicting the liquefaction-induced displacements of quay wall is a key aspect of the seismic design. In the first phase of this consecutive three-year project, a series of centrifuge modeling on the liquefaction of sand tested in a laminated box subjected to various input horizontal excitation will be conducted. A CPT system and a bender elements system will be developed for characterizing the dynamic properties of the tested ground during flight. These tests aim to understand the deformation mechanism of liquefied sand and the degradation of stiffness and strength of liquefied sand during and after earthquakes. The shear wave velocity of and the stress-strain relation of sand in the process of liquefaction based on a 1-D shear beam model will be developed. The evolution of shear wave velocity and the pore water pressure generation will be discussed In the second phase of the project, a series of centrifuge modeling tests with dense instrumentation will be performed to investigate the seismic response of a caisson type quay wall embedded in various ground conditions. A method considering both the rotational model and the sliding mode will be used to evaluate the stability of quay wall during earthquakes. In the third phase, the centrifuge modeling for the practical measures and the rehabilitation of the damaged quay wall will be also conducted to investigate the effectiveness of various countermeasures and finally an appropriate design methodology in the performance design base to evaluate the responses of caisson-type quay wall subjected to earthquake-induced liquefaction will be proposed. 研究期間 : 9808 ~ 9907
