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  • 學位論文

小型振動台之模型邊坡動態試驗研究

Dynamic Test of Model Slope Using Small Shaker

指導教授 : 林美聆

摘要


一九九九年九月二十一日,集集大地震襲擊中台灣,造成人員傷亡、房屋倒塌,許多邊坡嚴重破壞,為更深入了解邊坡之破壞機制,林美聆與王國隆自二○○三年起於國家地震中心進行「大型模型邊坡之振動台試驗」,探索邊坡之動態行為。但礙於大型試驗試體準備時間較長及經費耗費甚鉅,為能於大型試驗進行前預先模擬,因此王國隆開發小型振動台,期利用小型土壤模型振動試驗,進行先期定性研究以降低大型試驗之風險,產生互補作用。 本研究以越南峴港砂為試驗材料,透過剪力波元件試驗與共振柱試驗獲得試驗土壤之動態特性,包括剪力波速、最大剪力模數及剪力模數和阻尼比對剪應變之關係曲線。利用小型振動台進行模型邊坡動態試驗,模擬邊坡受震情形,藉由加速度計記錄與影像判視,觀察其受震行為。最後採用FLAC程式分析並驗證模型邊坡試驗之結果,配合STABL程式與Meymand(1998)之模型相律關係,比較模型與原型間之差異。 試驗結果發現振動台之振動模式,可產生頻率7赫茲,加速度振幅0.2g之簡諧振動,使模型邊坡產生近似圓弧型之淺層滑動破壞。而相對密度較低(約40%)之模型邊坡試體,其坡面滑動破壞較相對密度較高者(約70%)發生時機早,主要滑動發生之延時短暫,滑動量大,坡面滑動速率高,試驗前後模型邊坡幾何形狀改變大。而當試體相對密度上升,模型箱邊界對試體之束制情形會愈加明顯,此時應妥善處理邊界以免影響試驗結果。 以FLAC程式模擬小型振動台模型邊坡試驗,可有效模擬分析試驗結果。以STABL程式進行擬靜態分析其臨界加速度大小,與試驗中是否發生破壞之趨勢一致。Meymand之模型相似律,確實可使剪應變量達到一定程度之相似,然而試體之剪力波速與剪力模數難以滿足相似律之要求,係導致誤差之主要原因之一。

並列摘要


The Chi-Chi earthquake struck the central Taiwan on September 21, 1999 and resulted in severe landslide hazard. In order to understand the dynamic slope behavior, Meei-Ling Lin and Kuo-Lung Wang(2005) conducted “large- scale model slope shaking table test” in National Center for Research on Earthquake Engineering since 2003. However, the large scale test is time consuming and difficult to prepare simple. Therefore, the small shaking table was developed to simulate the large scale test and to perform qualitatively preliminary researches to lower the risk of large scale test. The small shaking table test is supplementary test to the large scale test. The Vietnam sand was used in this research, its dynamic characters, including shear wave velocity, maximum shear modulus, and the relationships of shear modulus and damping ratio versus shear strain were determined. Model slope test using small shaker were executed to simulate and observe the dynamic behavior of slope. Finally, the test results were verified and compared with results of prototype using FLAC, STABL, and similitude law proposed by Meymand(1998). The result indicates that the small shaker which generated simple harmonic vibration with frequency 7Hz and acceleration amplitude of 0.2g induced circular shallow failure of model slope. The slope failure of model slope with lower relative density, about 40%, than the model slope with higher relative density, and with about 70%, occurred earlier, within shorter duration, larger slip volume and faster slipping rate, and resulting more change in shape. The constraint of model box boundaries becomes more significant while samples’ relative density increased. The FLAC program used in this study appeared to be able to effectively analyze small-scale model slope. The critical acceleration computed using STABL in the pseudo-static is consistent with the model slope failure condition. The similitude law by Meymand appeared to satisfy the similarity between model and prototype in shear strain, however, due to the limitation in scaling of shear wave velocity and shear modulus, error was introduced.

參考文獻


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被引用紀錄


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曾美綺(2017)。地表地形對地震震波反應影響之數值模擬〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU201702675
陳俊甫(2015)。地形對地表放大效應之影響〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2015.01796
藍詩婷(2014)。地形對地震震波反應之影響〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2014.01284
黃靖雅(2013)。地震引致邊坡崩塌之影響範圍與滑動量數值模擬〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2013.00117

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