應用時域反射法於地層下陷監測之改善研發;Improvement of subsidence monitoring using Time Domain Reflectometry

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题名:	應用時域反射法於地層下陷監測之改善研發;Improvement of subsidence monitoring using Time Domain Reflectometry
作者:	簡煒峰;Chien, Wei-Feng
贡献者:	土木工程學系
关键词:	地層下陷;時域反射法;自動化;Subsidence;Time Domain Reflectometry (TDR);Automatic monitoring
日期:	2017-08-24
上传时间:	2017-10-27 12:18:59 (UTC+8)
出版者:	國立中央大學
摘要:	摘要地層下陷的問題在台灣日益嚴重，而根本瞭解沉陷的機制才能擬定減緩沉陷行為的方法。由於台灣西部的沖積扇平原含有多個含水層與阻水層，要瞭解沉陷行為必須監測各個壓縮層的沉陷情形。現有的磁環式監測井可以達到分層監測，但是此方法的人為誤差降低了沉陷精確度，而且無法即時反應沉陷行為。為此，本研究參考既有時域反射方法(Time Domain Reflectometry, TDR) 於沉陷量測之初步建議，以監測各個壓縮層的沉陷行為，不僅可以達到分層監測的目的，自動化監測去除了人為誤差的影響。本研究延續陳震紘（2014）之初步研究成果，採用漸變型金屬沉陷計以及發泡性聚苯乙烯(Expandable Polystyrene, EPS) 之非金屬沉陷計合併而成新式沉陷計，並提出多種判斷沉陷計位置的方法。此外，面對長距離傳輸造成的TDR 波形衰減問題，本研究建造一大型物理模型進行水中試驗，模擬地下水位變化時，波形衰減以及波形偏移之行為。當水位上升4 m，波形向下與向上振幅分別衰減了55%與80%，而最小與最大偏移量分別為4.53cm/m、8.64 cm/m。但於侷限含水層之實際沉陷計位移評估下，試驗結果顯示不受水深變化影響，其量測精度為0.97 mm，量測準確度為 0.90 mm，因此本研究初步建議本研發之沉陷計仍以侷限含水層為優先，但目前初步評析可適用範圍為30 m。本研究為改善波形衰減問題，提出一沉陷計分段式串接概念，藉由改變電磁波傳遞路徑以減少衰減行為，分析結果發現波形仍有產生衰減，但量測範圍大幅提昇至43 m。綜合上述試驗結果，本研究認為TDR 沉陷監測方法可應用於淺層之沉陷自動化監測，若是沉陷井建置於自由含水層，則可透過本研究中的波形偏移與水位關係，扣除偏移後求得實際沉陷量。關鍵詞：地層下陷、時域反射法、自動化;Abstract Since the problem of subsidence becomes serious recently in Taiwan, understanding the trend and mechanism of subsidence for reducing the influence is much essential and needed. The region in western Taiwan, however, consists of several aquifers and aquitards, it requires kinds of multilevel measurement methods for subsidence profiling. The public method now is the multi-depth subsidence leveling with magnetic rings, but it has apparent measurement error and lacks temporal resolution due to the manual manipulation. To provide an automatic and high accuracy instrumentation, this study improved Time Domain Reflectometry (TDR) as the core technology to measure subsidence based on the designs of Chen(2014). New subsidence sensor and related data reduction method have been validated to decrease the measurement error in the laboratory. To quantify the TDR wave attenuation and measurement error, which may be affected by groundwater variation, a 6 m physical model is built for such scenario. While water level rises 4 m, minimum and maximum amplitudes of TDR subsidence sensor wave decrease 55% and 80%, and the related error are 4.53 cm/m and 8.64 cm/m. The measurement precision and accuracy are 0.97 mm and 0.90 mm, respectively. Nevertheless, the signal decay due to the long transmission line is inevitable. A novel multi-section connection schema is now proposed and under testing to solve the aforementioned problem, it increases the measuring range from 30 m to 43 m. Keywords: Subsidence, Time Domain Reflectometry (TDR), automatic monitoring.
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