철근콘크리트 터널 라이닝 모형을 활용한 GPR 신호 특성 연구

초록

In the case of cast-in-place concrete linings of tunnels, there is a risk that the design thickness may not be secured or a cavity may occur on the back side. Therefore, in this study, we constructed a test model to propose a GPR analysis technique for evaluating the condition of reinforced concrete linings and back side. We carried out GPR tests and analyses of the test model. The specimen was composed of three sections: double-rebar, single-rebar, and plain(non-reinforced) concrete, considering the case of a specimen that could be encountered in the field. Each section included the same three types of cavities, so that signals for the cavity could be compared for each section condition. In the test, the applicability of each frequency was compared by using antennas with three frequencies: 400MHz, 900MHz, and 1600MHz. Since the cavity may be filled with air or water depending on the field conditions, this can be taken into account in the test model. Although the electromagnetic wave of GPR has the characteristic of being completely reflected from the metal, the reflected wave from the internal cavity could be clearly confirmed even in the reinforcing state. It was also confirmed that the reflected wave characteristics of electromagnetic waves changed depending on water or air. Therefore, the application of GPR to the evaluation of reinforced concrete lining and back side condition is effective, and it is judged that it is possible to propose a quantitative estimation method for the condition of reinforced concrete lining.

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