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2024 Vol.26, Issue 5

Research Paper

Integrity evaluation of rock bolt installed in rock slope using sound waves

음파를 이용한 암반사면에 설치된 록볼트의 건전도 평가

Jong-Sub Lee1
,
Jung-Doung Yu2*
이 종섭1
,
유 정동2*
1Professor, School of Civil, Environmental and Architectural Engineering, Korea University
2Assistant Professor, Dept. of Civil Engineering, Jeonbuk National University
1정회원, 고려대학교 건축사회환경공학부 교수
2정회원, 전북대학교 토목공학과 조교수
*Corresponding Author
30 September 2024. pp. 385-401
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Abstract

Rock bolts play a crucial role in reinforcing rock slopes. However, a poorly grouted rock bolt occasionally occurs, potentially compromising the stability of a rock slope. The purpose of this study is to evaluate the integrity of a rock bolt using sound waves. In experiments, a total of five rock bolts are prepared, one of which is intact while the other four are poorly grouted. The grouted ratios of four poorly grouted rock bolts are 80%, 70%, 60%, and 50%, respectively, and nongrouted sections are introduced at the upper part of the rock bolts. Rock bolts are installed in a concrete block to simulate rock bolts embedded in a rock slope. Sound waves are generated by impacting the head of the rock bolt and measured using the built-in microphone of a smartphone. Measured sound waves are analyzed in frequency domain through Fourier transform. Results show that the predominant frequency of sound waves decreases as the grouted ratio decreases. This study suggests that the predominant frequency of sound waves can be an effective indicator for evaluating the integrity of the rock bolt.

Keywords
Integrity
Predominant frequency
Rock bolt
Smartphone
Sound waves

록볼트는 암반사면을 보강하는데 중요한 역할을 한다. 하지만, 그라우트 충전 상태가 불량한 록볼트가 발견되는 사례가 종종 발생하고 있으며, 이는 암반사면의 안정성에 악영향을 줄 수 있다. 본 연구는 음파를 이용하여 록볼트의 견전도를 평가하기 위해 수행되었다. 본 연구에서는 총 다섯 개의 록볼트 시험체를 준비하였으며, 이 중 하나는 그라우트로 완전히 충전된 록볼트이며, 네 개는 그라우트 충전 상태가 불량한 록볼트로 준비하였다. 그라우트 충전이 불량한 부분은 록볼트의 두부에 모사하였으며, 그라우트 충전비율은 80%, 70%, 60%, 50%로 준비하였다. 제작한 록볼트 시험체는 콘크리트 블록 내에 설치하여 암반에 근입되어 있는 환경과 유사하게 조성하였다. 록볼트의 두부를 해머로 타격하여 음파를 발생시켰으며, 스마트폰에 내장되어 있는 마이크로 음파를 측정하였다. 측정한 음파는 푸리에 변환을 통해 주파수 영역에서 분석하였다. 그 결과, 록볼트의 그라우트 충전비율이 낮을수록 측정된 음파의 우세주파수가 감소하였다. 본 연구는 스마트폰의 내장 마이크를 이용하여 측정한 음파의 주파수 특성이 록볼트의 건전도를 평가하는 데 있어 유용한 지표가 될 수 있음을 보여준다.

키워드
건전도
우세주파수
록볼트
스마트폰
음파
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Information
  • Publisher :Korean Tunneling and Underground Space Association
  • Publisher(Ko) :한국터널지하공간학회
  • Journal Title :Journal of Korean Tunnelling and Underground Space Association
  • Journal Title(Ko) :한국터널지하공간학회 논문집
  • Volume : 26
  • No :5
  • Pages :385-401
  • Received Date : 2024-04-01
  • Revised Date : 2024-05-20
  • Accepted Date : 2024-05-29
  • DOI :https://doi.org/10.9711/KTAJ.2024.26.5.385
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