振動台模型邊坡滑移行為之數值模擬

Numerical Simulation of Landslide Behavior from Shaking Table Test

蕭宇翔(Yu-Hsiang Hsiao)

指導教授 ： 林美聆

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01322

摘要

邊坡問題通常規模很大，材料組成複雜，並不容易利用全尺寸的現地試驗觀察破壞機制。透過模型相似性與問題的簡化，可以縮小尺度並建立物理模型試驗，利用振動台試驗與離心機試驗，可以在1-g及N-g的條件下，觀測大地工程問題的破壞機制。林美聆、王國隆於2003年至2009年在國家地震工程研究中心進行八組大型振動台試驗，模擬邊坡受震行為。本研究由試驗結果之加速度反應、PIV影像分析以及標點位移量測，觀察邊坡受震反應，推測破壞時間。以有限差分軟體FLAC模擬邊坡模型受震反應，推測可能之破壞面位置，由應力路徑與頻譜分析推測可能之滑動時間及臨界加速度。利用建立之數值模型，針對大型振動台試驗加入垂直振動與否之影響進行討論。
振動加載過程乃由小至大，邊坡開始產生淺層滑動時，滑動範圍僅在邊坡坡面，坡頂及坡趾並無產生明顯位移，試體內部加速度反應並不明顯。邊坡產生大規模滑動時，坡趾開始往下坡方向移動，坡頂後方產生張裂縫，試體內部加速度相位反應不同步。數值模擬由模型內部網格變形呈現夾心狀時定義為大規模滑動之時間，以坡趾延伸至坡頂之剪應變分佈且網格應力碰觸到破壞包絡線做為大規模滑動之範圍。本研究利用數值軟體FLAC分別模擬無垂直振動之試驗及加入垂直振動之試驗，發現兩組試驗在水平位移變化及剪應變分佈範圍以加入垂直振動之試驗較為廣泛。最後再比較各組之間不同的加速度歷時及破壞行為，找出大型振動台試驗之淺層破壞及深層破壞之型式，以及各分析方法所對應之破壞時間。

關鍵字

振動台試驗 ； 模型邊坡 ； 破壞面 ； 數值模擬

並列摘要

Geotechnical engineers usually encounter large-scale slope problems with complex material composition. Thus, it is hard to use full-size in-situ test to observe the failure mechanism. By law of similitude and simplification, model tests were established to simulate 1-g gravitational field or n-g gravitational field by shaking table test or centrifuge test. This study utilized to the large-scale model slope shaking table tests of the model slope conducted by Lin and Wang from 2003 to 2009 at NCREE. The failure time was estimated according to the acceleration response record, particle image velocimetry (PIV) analysis, and marker displacement measurements. The failure plane was estimated from results of the finite differentice analysis. The critical acceleration and failure time was estimated based on stress path and frequency spectrum analysis during loading. By using the numerical analysis, the effects of vertical vibration or not were discussed.
Shallow failure sliding occurred on the slope surface, no significant displacement on the crest and toe, and no obvious difference in acceleration responses were observed. As deep-seated landslide developed, the crest and toe started moving down-slope. The crack occurred behind the crest, and phase of acceleration response became shifted. The failure time was defined when the grid start to deform in deeper. The failure surface was defined by maximum shear strain distribution which is from toe to crest and the stress of grids close to failure envelope. Based on results of numerical simulation of specimen which is without vertical vibration and specimen which is with vertical vibration, it was found that the range of horizontal displacement and shear strain increment of specimen with vertical vibration is more than specimen without vertical vibration.At last, compared with acceleration history and failure behavior were made to determine, find out the mode of shallow failure, deep failure, and failure time, then summarize the data of large shaking table test.

並列關鍵字

shaking table test ； slope ； failure surface ； numerical analysis

參考文獻

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