| 摘要: | 臺灣位於菲律賓海板塊和歐亞板塊的聚合邊界，地震發生頻繁，且臺灣約有三分之一的地形為平原地區，多屬地質軟弱的沖積地層，地下水位面高，使土壤液化潛能高，當大規模地震作用時，即可能發生土壤液化。版樁牆具有良好的經濟性及施工性，因此常被作為河岸、港灣、碼頭的擋土系統，該區域地下水位面非常高，因此通常有較高土壤液化潛能，當土壤液化發生時，版樁牆會因土壤大變形而傾倒及損毀。
地震強度與延時皆與地震災害影響的嚴重程度呈正相關，為瞭解加速度振幅與週數對液化砂土中版樁牆的受振反應，本研究利用中央大學地工離心機進行動態離心模型試驗。在24 g重力場中，試驗輸入基盤振動頻率為1 Hz，最大加速度振幅及持續週數分別為0.1 g-36 cycles、0.14 g-19 cycles、0.17 g-10 cycles以及0.2 g-5 cycles的非等振幅正弦波，並透過加速度計、孔隙水壓計、線性可變差動變壓器、圓錐貫入試驗儀、地中位移計與地表追蹤計記錄土壤受震反應。
試驗結果顯示，土壤受振強度與液化深度呈正相關，隨著液化深度增加，對地表產生的水平位移量也會增加，土壤受振持續時間亦會對液化土壤造成位移增加，因此地表位移相近;當輸入振幅與週數呈反比而愛氏震度相同時，造成牆傾角相近，然而土壤受振強度大到牆前土壤也液化後，牆傾角會明顯大於其他愛氏震度相同的小振;在版樁牆受振後土壤超額孔隙消散階段，版樁牆不再繼續位移，牆後土壤會繼續沉陷。
;The plain of west Taiwan is formed of soft alluvium ground with a high groundwater level. As Taiwan is located on the Circum-Pacific Seismic Belt, earthquakes occur frequently and can lead to soil liquefaction on the alluvium ground. Sheet pile walls are often used as a retaining system at riverbanks, harbors, and piers due to their cost-effectiveness, convenience, and constructability. Near the river, soil deposits are composed of alluvial soils and groundwater levels are very high, therefore soil liquefaction are usually more common around this area. When soil liquefaction occurs, the sheet pile walls would fall or become damaged as a result of soil deformation.
Both the intensity and duration of the earthquake are positively correlated with the severity of the earthquake disaster. In order to understand the seismic response behavior of sheet pile walls in saturated soil caused by these two variations, four dynamic centrifuge tests were conducted to simulate the sheet pile wall in liquefiable ground, and used the centrifugal model scaling law to simulate the seismic response of the sheet pile wall in a mixed soil layer of saturated silica sand with relative density of 90% and 60%, and thicknesses were 1m and 4m, respectively. In the 24 times gravitational field, frequency of input motion is 1 Hz. The maximum acceleration of input motion and the cycles of the maximum acceleration of the motion are 0.2 g-5 cycles, 0.17 g-10 cycles, 0.14 g-19 cycles, 0.11 g-36 cycles of ramped sine waves, respectively. In this test, accelerometers, linear variable differential transformers, pore water pressure transducers, spaghetti and surface marker were arranged to measure the response of the model. The test results show that 1. Liquefaction depth and the intensity of input motion are positively correlated; 2. As the input motions have the same AI, if the amplitude is big enough to lead to front wall soil liquefaction occur, the wall will tilting angle much more than other smaller motion; 3. In the stage of dissipation period, the sheet pile wall will no longer continue to move, and the backwall soil will continue to settle. |
