Journal of Korean Tunnelling and Underground Space Association (한국터널지하공간학회 논문집)

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
권호 표지
DOI QR코드

DOI QR Code

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

음파를 이용한 암반사면에 설치된 록볼트의 건전도 평가

  • Jong-Sub Lee (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Jung-Doung Yu (Dept. of Civil Engineering, Jeonbuk National University)
  • 이종섭 (고려대학교 건축사회환경공학부) ;
  • 유정동 (전북대학교 토목공학과)
  • Received : 2024.04.01
  • Accepted : 2024.05.29
  • Published : 2024.09.30
Download PDF
⟨ Previous Next ⟩

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.

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.

Keywords

Acknowledgement

본 연구는 정부(과학기술정보통신부)의 재원으로 한국연구재단의 지원을 받아 수행되었습니다. 이에 감사드립니다(NRF-2021R1A5A1032433 & NRF-2021R1C1C2005687).

References

  1. Bacic, M., Gavin, K., Kovacevic, M.S. (2019), "Trends in non-destructive testing of rock bolts", Gradevinar, Vol. 71, No. 10, pp. 823-831.
  2. Bacic, M., Kovacevic, M.S., Juric Kacunic, D. (2020), "Non-destructive evaluation of rock bolt grouting quality by analysis of its natural frequencies", Materials, Vol. 13, No. 2, 282.
  3. Bennett, W.R. (2018), The Science of Musical Sound, Springer, New York, p. 440.
  4. Fahy, F., Thompson, D. (2015), Fundamentals of Sound and Vibration, CRC Press, London, p. 516.
  5. Fletcher, N.H., Rossing, T.D. (1998), The Physics of Musical Instruments, Springer-Verlag, New York, p. 756.
  6. Giurgiutiu, V. (2014), Structural Health Monitoring with Piezoelectric Wafer Active Sensors, Elsevier, Amsterdam, p. 1024.
  7. Godfrey, D.E., Kuchar, N.R. (1977), Method of testing the integrity of installed rock bolts, U.S. Patent No. 4,062,229, U.S. Patent and Trademark Office, pp. 1-7.
  8. Hartman, W., Lecinq, B., Higgs, J., Tongue, D. (2010), "Non destructive integrity testing of rock reinforcement elements in Australian mines", Proceedings of the Underground Coal Operators' Conference, University of Wollongong, Australia, pp. 161-170.
  9. Holland, D.C. (1993), The behaviour of resin bonded rock bolts and other anchorages, subjected to close proximity blasting, Doctoral Dissertation, University of Aberdeen, p. 224.
  10. Ivanovic, A., Neilson, R.D. (2008), "Influence of geometry and material properties on the axial vibration of a rock bolt", International Journal of Rock Mechanics and Mining Sciences, Vol. 45, No. 6, pp. 941-951. https://doi.org/10.1016/j.ijrmms.2007.10.003
  11. Ivanovic, A., Neilson, R.D. (2013), "Non-destructive testing of rock bolts for estimating total bolt length", International Journal of Rock Mechanics and Mining Sciences, Vol. 64, pp. 36-43. https://doi.org/10.1016/j.ijrmms.2013.08.017
  12. Ivanovic, A., Neilson, R.D., Rodger, A.A. (2001), "Lumped parameter modelling of single-tendon ground anchorage systems", Geotechnical Engineering: Proceedings of the Institution of Civil Engineers, Vol. 149, No. 2, pp. 103-113. https://doi.org/10.1680/geng.2001.149.2.103
  13. Kelly, A.M., Jager, A.J. (1996), Critically evaluate techniques for the in situ testing of steel tendon grouting effectiveness as a basis for reducing fall of ground injuries and fatalities, Safety in Mines Research Advisory Committee, GAP 205, p. 65.
  14. Kim, T.G., Lee, S.W., Jang, S.H. (2009), "Design and construction of support system: rock bolt and cable bolt", Magazine of Korean Tunnelling and Underground Space Association, Vol. 11, No. 1, pp. 9-29.
  15. Kinsler, L.E., Frey, A.R., Coppens, A.B., Sanders, J.V. (2000), Fundamentals of Acoustics, John Wiley & Sons, New Jersey, p. 548.
  16. Lee, J.S., Yu, J.D. (2024), "Nondestructive evaluation of grout defect in rock bolt using electromagnetic waves", Developments in the Built Environment, Vol. 17, 100365.
  17. Madenga, V., Zou, D.H., Zhang, C. (2006), "Effects of curing time and frequency on ultrasonic wave velocity in grouted rock bolts", Journal of Applied Geophysics, Vol. 59, No. 1, pp. 79-87. https://doi.org/10.1016/j.jappgeo.2005.08.001
  18. Masoudi, R., Sharifzadeh, M., Ghorbani, M. (2019), "Partially decoupling and collar bonding of the encapsulated rebar rockbolts to improve their performance in seismic prone deep underground excavations", International Journal of Mining Science and Technology, Vol. 29, No. 3, pp. 409-418. https://doi.org/10.1016/j.ijmst.2018.09.001
  19. Milne, G.D. (1999), Condition monitoring & integrity assessment of rock anchorages, Doctoral Dissertation, University of Aberdeen, p. 239.
  20. Photinos, P. (2017), Musical Sound, Instruments, and Equipment, Morgan & Claypool Publishers, San rafael, CA, p. 166.
  21. Raichel, D.R. (2006), The Science and Applications of Acoustics, Springer, New York, p. 660.
  22. Rao, S.S. (2011), Mechanical Vibrations, Prentice Hall, New Jersey, p. 1084.
  23. Rao, S.S. (2019), Vibration of Continuous Systems, Wiley, New Jersey, p. 816.
  24. Rossing, T.D., Moore, R.F., Wheeler, P.A. (2013), The Science of Sound, Pearson, London, p. 776.
  25. Sundholm, S. (1987), "The quality control of rock bolts", Proceedings of the 6th ISRM Congress, Montreal, pp. 1255-1264.
  26. Thurner, H. (1996), Rock bolting - Reference bank, Report No. AMFO 84-0847, Translated by the Council for Scientific and Industrial Research (CSIR), Courtesy of Sweden, Geodynamik AB, Stockholm, p. 33.
  27. Thurner, H.F. (1988), "Boltometer - Instrument for non-destructive testing of grouted rock bolts", Proceedings of the 2nd International Symposium on Field Measurements in Geomechanics, Kobe, pp. 135-143.
  28. White, H.E., White, D.H. (2014), Physics and Music: The Science of Musical Sound, Courier Corporation, North Chelmsford, MA, p. 448.
  29. Wu, R., Xu, J., Li, C., Zhou, B., Ma, Q., Wang, Z. (2012), "Stress wave propagation in supporting bolts: a test for bolt support quality", International Journal of Mining Science and Technology, Vol. 22, No. 4, pp. 567-571. https://doi.org/10.1016/j.ijmst.2012.01.021
  30. Wyllie, D.C. (2017), Rock Slope Engineering: Civil Applications, CRC Press, Boca Raton, FL, p. 620.
  31. Yu, J.D., Bae, M.H., Lee, I.M., Lee, J.S. (2013), "Nongrouted ratio evaluation of rock bolts by reflection of guided ultrasonic waves", Journal of Geotechnical and Geoenvironmental Engineering, Vol. 139, No. 2, pp. 298-307. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000767
  32. Yu, J.D., Byun, Y.H., Lee, J.S. (2019), "Experimental and numerical studies on group velocity of ultrasonic guided waves in rock bolts with different grouted ratios", Computers and Geotechnics, Vol. 114, 103130.
  33. Yu, J.D., Lee, J.S. (2020), "Smart sensing using electromagnetic waves for inspection of defects in rock bolts", Sensors, Vol. 20, No. 10, 2821.
  34. Zima, B., Rucka, M. (2017), "Non-destructive inspection of ground anchors using guided wave propagation", International Journal of Rock Mechanics and Mining Sciences, Vol. 94, pp. 90-102. https://doi.org/10.1016/j.ijrmms.2017.03.005
  35. Zou, D.H., Cui, Y., Madenga, V., Zhang, C. (2007), "Effects of frequency and grouted length on the behavior of guided ultrasonic waves in rock bolts", International Journal of Rock Mechanics and Mining Sciences, Vol. 44, No. 6, pp. 813-819. https://doi.org/10.1016/j.ijrmms.2006.12.002
  36. Zou, D.H.S. (2004), "Analysis of in situ rock bolt loading status", International Journal of Rock Mechanics and Mining Sciences, Vol. 41, No. Supplement 1, pp. 762-767. https://doi.org/10.1016/j.ijrmms.2004.03.132