Improved TDR Deformation Monitoring by Integrating Centrifuge Physical Modeling

NCUIR > Engineering College > Graduate Institute of Civil Engineering > Electronic Thesis & Dissertation > Item 987654321/83043

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/83043

Title:	Improved TDR Deformation Monitoring by Integrating Centrifuge Physical Modeling
Authors:	陳文研;Tran, Van-Nhiem
Contributors:	土木工程學系
Keywords:	Time domain reflectometry;shear deformation quantification;centrifuge modelling.;Time domain reflectometry;shear deformation quantification;centrifuge modelling.
Date:	2020-07-31
Issue Date:	2020-09-02 14:31:22 (UTC+8)
Publisher:	國立中央大學
Abstract:	邊坡災害是在邊坡上土壤或岩石崩壞的現象。監測邊坡災害一直都是棘手的問題，尤其是在山區，由於復雜的地形和地理環境，難以安裝監測系統。邊坡監測技術不僅包括地面衛星圖像分析和全球定位系統（GPS），還包括諸如傾斜儀和時域反射法（TDR）等監測方法。儘管上述的方法可以提供邊坡大面積的監測範圍，但是在使用 GPS 時仍具有侷限性，例如追求更高的精度，又或者取得目標地之滑坡平面的深度。另一方面，TDR 作為地下邊坡監測預警系統，已經成功驗證在不同現地測試下的可行性。而 TDR 可涉及到監測連續的剪切變形。有研究者在實驗室內進行剪切和壓痕實試，且對於 TDR 反射係數與剪切位移進行了定量分析，但是 TDR 仍面臨著一些問題，由於上覆壓力對於反射係數仍相對不敏感，所以反射係數對剪切位移的精確定量仍是一項挑戰。為了解決上述問題，本研究提出將離心機逆斷層破壞模型與 TDR 結合來模擬纜線剪切變形的方法。為了符合離心試驗的縮放定律，對於小直徑柔性同軸電纜進行第一次的修改，並與直接剪力實驗進行評估。然後在不同重力的離心機模型中，通過增加 N 倍的重力場，與 1/N 比例的實驗模型來進行研究。本研究執行三個部分，第一，實驗室直接剪力實驗表明，改良後的同軸電纜在 0.5mm 的極小剪切位移下，靈敏度有顯著地提高。第二，在離心機物理實驗中，通過具有剪切帶和較大剪切位移的逆斷層破壞模型成生剪切平面，進而得到 TDR 波形與剪切變形之間的相關性。基於上述的實驗，包括尖峰反射係數和區域積分以及相應的剪切位移，對其進行進一步的定量分析。而在最後發表了 TDR 離心機模型建模之指南。;Landslide disaster is a result of the failure of the soil or rock slope. Landslide monitoring is the most critical challenging issue especially in the mountain where is difficult for installation of the monitoring system because of complex topography and geography. Landslide monitoring techniques include not only satellite images analysis and Global position system (GPS) for the land surface target, but also the underground methods such as inclinometer and Time Domain Reflectometry (TDR). Despite providing the early warning with a continuous displacement of the slope surface, GPS applied in landslide monitoring still exists a limitation on indicating higher accuracy and localizing the shear plane in depth. On the other hand, TDR as a warning system in landslide monitoring underground has been validated with different field studies in slope monitoring. TDR involves continuously detecting shear surface and exactly identifying shear deformity. Although previous studies of laboratory shear and indentation tests have quantified shear displacement based on the TDR reflection coefficient, TDR suffers challenges for precise quantification of shear displacement from the reflection coefficient influenced by several factors, and it relatively insensitive due to artificial overburden pressure in the laboratory test. To address the abovementioned problems, this study proposed TDR integrated with centrifuge reverse fault modeling to simulate sliding at depth. To fit the centrifuge test scale, a flexible and small diameter coaxial cable was first modified and evaluated with the simple direct shear test. Then the reverse fault modeling was used to simulate the shear plane in the centrifuge modelling at the different earth gravity level. The prototype model can investigate through the 1/N scale model by enhancing the N time level earth gravity field. As testing results, this study carries out three main major parts. First, the laboratory direct shear testing showed the modified coaxial cable has dramatic improvement in the sensitivity at very small-scale shear displacement at 0.5 mm. Second, in the centrifuge physical model, the shear plane can be generated by reverse fault modeling with shear bandwidth and large shear displacement, and the quantification of the correlation between the TDR waveform and shear deformation was accordingly revealed. The quantification was further analyzed based on two methods including the peak reflection and the integration area with corresponding shear deformation. Finally, general guidelines for TDR landslide modeling in centrifuge was suggested in this study.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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