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(사)한국터널지하공간학회

ISSN : 2233-8292

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Vol.9 No.4

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Guidedwave-induced rockbolt integrity using Fourier and wavelet transforms

(사)한국터널지하공간학회 / (사)한국터널지하공간학회, (P)2233-8292; (E)2287-4747
2007, v.9 no.4, pp.403-413




& (2007). Guidedwave-induced rockbolt integrity using Fourier and wavelet transforms. (사)한국터널지하공간학회, 9(4), 403-413.

Abstract

rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators for the evaluation of rock bolt integrity.

keywords
Energy velocity, Fourier transform, guided wave, non-destructive test, spectrum, wavelet transform, Energy velocity, Fourier transform, guided wave, non-destructive test, spectrum, wavelet transform, 에너지 속도, 푸리에 변환, 유도파, 비파괴 시험, 스펙트럼, 웨이브렛 변환

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