振動台模型相似律及滑移行為分析

Similitude and Landslides Behavior for Shaking Table Test

鄒銘徽(Ming-Huei Zou)

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(2011年)

https://doi.org/10.6342/NTU.2011.01595

摘要

大地工程問題通常規模大，材料組成複雜，不容易利用全尺寸的現地試驗觀察破壞機制。透過模型相似律與問題的簡化，可以縮小尺度建立物理模型試驗，在1-g的條件下來觀察大地工程問題的破壞機制。本研究採用林美聆、王國隆於2009年9月於國家地震中心所進行之大型振動台試驗資料，由加速度反應、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，由應力路徑與加速度歷時推測可能之臨界加速度。利用建立之數值模型，針對大型振動台試驗模型與原型之模型相似性進行討論。
邊坡淺層崩滑時，滑動範圍僅發生在邊坡坡面，坡頂及坡趾並無明顯位移產生，試體內部加速度反應並不明顯。邊坡產生大規模深層塊體滑動時，坡頂及坡趾開始往下坡方向移動，坡頂後方產生裂縫，試體內部不同深度之加速度相位反應不同步。由標點位移量測定義當坡頂裂縫產生後，坡頂標點移動速度開始改變時之位移量為臨界位移量，當FLAC計算出邊坡模型之水平位移量達臨界位移量時，定義此時最大剪應變範圍為破壞面，其延伸至坡頂位置與影像記錄所量測到之位置相近。藉由Meymand（1998）所提出之模型相似律，可以由模型邊坡之試驗結果預測原型邊坡之受震反應。本研究利用數值軟體FLAC分別模擬大型振動台邊坡模型試驗，以及原型邊坡之受震反應，發現兩組邊坡之時間長度正規化相對水平位移變化以及剪應變分佈相當一致。因此，在不考慮邊界效應以及能量消散之情況下，可使用由邊坡模型試驗所建立之數值模型模擬現地邊坡受震反應行為。

關鍵字

震動台試驗 ； 模型相似律 ； 邊坡 ； 破壞面 ； 臨界加速度

並列摘要

Geotechnical engineers usually encounter large-scale 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, small-scale model tests were established to simulate 1-g gravitational field. This study was according to the large-scale model slope shaking table tests of the model slope conducted by Lin and Wang in September 2009 at NCREE. The failure time was estimated according to the acceleration responses, particle image velocimetry (PIV) analysis, and marker displacement measurements. The failure plane was estimated from results of the finite differential numerical analysis. The critical acceleration was estimated based on stress path during loading. By using the established numerical mode, the similarity between model and prototype was 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 landslide occurred, the crest and toe started moving toward down-slope. The crack occurred behind the crest, and the acceleration response became shifted. After the crack occurred and the markers at the crest started moving rapidly, the critical displacement was defined by the marker's horizontal displacement. The failure surface was defined by maximum shear strain distribution when the numerical model's horizontal displacement was equal to critical displacement. The location of failure surface at the top of the slope is similar to the crack measured from image. According to the law of similitude proposed by Meymand (1998), the prototype seismic slope response could be predicted from model test. Based on results of numerical simulation of prototype seismic behavior, it was found that the normalized deformation and shear strain distribution were quite similar. Therefore, the numerical model established according to the slope model test could be used to simulate in-situ seismic slope response when boundary effects and energy dissipations were insignificant.

並列關鍵字

shaking table test ； law of similitude ； slope ； failure surface ； critical acceleration

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