基盤土壤液化對上方土堤位移的影響;Effect of Foundation Soil Liquefaction on Deformation Behavior of Embankment

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Title:	基盤土壤液化對上方土堤位移的影響;Effect of Foundation Soil Liquefaction on Deformation Behavior of Embankment
Authors:	黃俊學;Huang, Jun-Xue
Contributors:	土木工程學系
Keywords:	離心模型試驗;土壤液化;側向滑移;土堤;centrifuge;liquefation;lateral spreading;embankment
Date:	2016-12-16
Issue Date:	2017-01-23 15:44:29 (UTC+8)
Publisher:	國立中央大學
Abstract:	臺灣位於歐亞板塊交界，地震頻繁發生，且臺灣西部平原區多屬地質軟弱的沖積地層，地下水位面高，因此這些區域的土壤液化潛能較高，當地震來臨時，很有可能發生土壤液化。若液化地盤上有一土堤結構，在受振引致土壤液化與側向移動的情況，會對土堤造成相當大的損害，因此了解基盤土壤液化對土堤結構的影響，並找出改善方法，是一個重要的課題。本研究進行一系列離心模型動態試驗，模擬土堤座落於均質地砂質地盤上的受振行為，藉由改變地盤的坡度與飽和條件，探討土堤及地盤在不同條件下，其動態反應與沉陷行為。試驗結果顯示，當試體受到非等振幅類正弦波的振動時，土壤液化會由試體之表層至深層依序發生，本研究稱此現象為「液化延遲」。傾斜2度的飽和地盤，因為地盤本身受到一靜態剪應力，受振時地盤的加速度反應會呈現不對稱的狀態。在地盤為乾砂條件時，土堤僅有受振引致的沉陷產生，然而地盤為飽和條件時，土堤不僅有受振引致的沉陷，亦有地盤液化後因超額孔隙水壓消散引致的壓密沉陷，且土堤於液化地盤之上的沉陷量為於乾砂地盤之上的10至15倍。此外，在所有的試驗中，土堤的沉陷皆為均勻沉陷之行為，且當同為乾砂地盤或是飽和地盤的條件下，土堤的沉陷量皆相近，表示地盤傾斜與否對土堤的沉陷行為影響不大，但是土堤在傾斜的飽和地盤上時，地盤液化後引致的側向滑移，會使土堤也隨之滑動，造成水平方向上位移。;The plain of west Taiwan is soft alluvium ground with high ground water level. Moreover, Taiwan is located at Circum-Pacific seismic belt, earthquakes usually occur and leading to soil liquefaction especially for the alluvium ground. At two sides of river, the embankment built on the liquefiable ground would cause significance damage during earthquake. Therefore, it needs to be understood the failure behavior of a gentle slope by soil liquefaction or lateral spreading. Several centrifuge shaking table tests were performed to simulate the behavior of embankment which construct on the liquefiable ground. The effects of soil liquefaction on the response of embankment are discussed. Test results show that liquefaction occurs in sequence from soil surface to deep soil layer when model subject an unequal-amplitude sinusoidal wave. In saturated inclined ground model, the acceleration amplitude is asymmetry due to static stress. In dry models, there is only immediate settlement of embankment cause by shaking. However, in saturated models, it includes immediate settlement cause and consolidation settlement cause by soil liquefaction, and the total settlement in saturated models is 10 to 15 times of total settlement of dry models. Moreover, embankment settles uniformly in all tests, and the settlement values are very close between flat and inclined ground, so the effect is slightly whether the ground is inclined or not. However, lateral spreading occur when soil liquefied in inclined ground model, therefore embankment also slide away for 1 meter on horizontal direction.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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