透地雷達應用於堤防掏空及板體潮濕檢測之研究

Inspection of Deteriorated Embankments and Concrete Structure with Different Moisture Content using Ground Penetration Rader

劉信邦(Xin-Bang Liu)

指導教授 ： 鄭家齊

朝陽科技大學/理工學院/營建工程系/碩士(2011年)

摘要

摘要
由於透地雷達對施測目標具有非破壞性，而近年來儀器設備與軟體不斷地更新進步，研究之目的是研究如何將透地雷達檢測運用於河海堤防掏空檢測與板體潮濕狀態檢測以及如何適當解釋檢測訊號。
本研究在板體潮濕狀態檢測實驗中利用B-scan鋼筋反應數位影像找尋對應之雙曲線，用來計算試體四種含水量之混凝土波速、介電常數，結果發現當混凝土之含水量越多時，混凝土波速會越小及介電常數會越大，所以含水量多寡，在透地雷達圖上有明顯之差異，而利用鋼筋首達波達到時間計算之波速與利用鋼筋半雙曲線曲率來計算之波速差異不大。
本研究在掏空實驗探討在混凝土板下方存在掏空時，透地雷達反應的變化，實驗變數包括十種掏空尺寸、三種檢測天線頻率，並以1½正弦波模擬電磁波脈波在混凝土與空隙介面及空隙與土壤介面反射訊號疊加結果，結果發現，兩介面反射波疊加時之相位與空隙尺寸的相對關係對訊號鑑別的影響相當明顯，可由此解釋不同頻率天線的掏空訊號。

關鍵字

透地雷達 ； 堤防掏空 ； 潮濕檢測

並列摘要

Abstract
Ground-penetrating radar (GPR) is a non-destructive testing facility. The testing equipments and softwares are updated progressively in recent years. The research aims to develop the technologies using GPR to detect the cavities under the concrete shell of sea or river embankment and to inspect the state of moisture of reinforced concrete plate which may be induced by water pipe leakage.
In this study, the state of moisture can be assessed by the hyperbolic shaped in the B-scan digital images produced by radar wave reflections from the reinforcing bar. The semi-hyperbolic curve fitting with the steel reflecting images can calculate the important parameters such as velocity and dielectric constant of the concrete. These parameters were obtained for the concrete specimens with four water contents. The results showed more the water content, less the velocity and larger the dielectric constant. So the image of steel bar in the ground-penetrating radar map can reveal the moisture condition in concrete. The velocity of concrete obtained from first time arrival of the wave reflected from the top surface of the steel bar divided by twice of the cover thickness and the one calculating from the curvature of the steel- semi-hyperbolic curve is very similar.
The other study discussed the change in response of ground-penetrating radar corresponding to different size of gap between the concrete shell and the earth infill. The experimental variables include the dimension of the gap and the frequency of detecting antenna. Two sets of 1 1/2 sine wave pulses superposed with variant time intervals is used to demonstrate the superposition of radar wave pulses reflected by the concrete-gap and gap-soil interfaces. It was found that the phase difference between the two superimposed reflecting signals corresponding to different gap dimensions plays a crucial part in cavity identification. These results also explained the signals obtained from different antenna frequencies for the embankment excavation problem.

並列關鍵字

Different Moisture Conternt ； Ground Penetration Rader ； Deteriorated Embankmen

參考文獻

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