Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
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New Gain Function Based on Attenuation Characteristics of Ballast Track for GPR Analysis

GPR 분석을 위한 자갈궤도 자갈의 감쇄특성을 이용한 이득함수 개발

  • Received : 2017.02.02
  • Accepted : 2017.03.24
  • Published : 2017.04.01
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Abstract

Ballasted track has been used as track system for more than 100 years. Ballasted track has advantages of low construction cost, flexible maintenance, low noise and vibration, and so on. However, ballasted track leads to continuous settlement which causes maintenance. Recently, increase in speed, traffic volume, and weight of train requires more frequent maintenance. Fouling, well-known phenomenon of accumulation of fine materials due to intrusion of subgrade and breakage of ballast materials, expedites the settlement (i.e., irregular settlement) of track. Ground Penetrating Radar (GPR) can be one of non-destructive tools that can evaluate fouling level of ballast. In this paper, a gain function based on the attenuation characteristics of ballast material is suggested in conjunction with Hilbert transform. Lab box tests and full-scale tests indicate that the suggested method reasonably classifies clean, fouled layers, and subgrade. However, additional study to eliminate effect of sleeper and to include the scattering features of the electromagnetic wave in ballast voids should be required in order to enhance the accuracy.

자갈궤도는 100여년 이상 전세계적으로 널리 사용되는 궤도구조로 저렴한 초기 건설비용, 유연한 유지보수와 진동 및 소음의 저감효과가 있지만, 열차운행에 따라서 지속적인 침하가 발생하는 단점이 있다. 이로 인해 지속적인 유지보수가 필요하며, 최근 열차의 속도, 용량, 중량의 증가로 유지보수비용이 증가하고 있는 실정이다. 파울링(fouling)은 노반 세립분이나 자갈입자가 파쇄되면서 발생한 세립분이 자갈 사이의 공극을 메우는 현상으로 배수가 나빠지고, 자갈궤도의 침하를 가속화시키는 등 자갈도상의 열화의 주원인으로 지목되고 있다. 본 논문에서는 GPR(Ground Penetrating Radar)을 이용하여, 도상의 상태를 평가 할 수 있는 분석방법을 제안하였다. 경험에 의존하는 기존의 분석기법을 대신하여, 고속선에 사용되는 자갈의 감쇠 특성을 반영한 이득함수(gain function)를 제안하였다. 실내 박스 실험과 실모형 실험을 통해 제안한 이득함수로 증폭한 GPR신호에 힐버트 변환을 추가로 적용하여 자갈층과 노반층에서 반사된 신호의 세기변화를 깊이에 따라 계산하였다. 이로부터 신호의 세기가 비교적 크게 변화하는 곳을 파울링층과 노반층의 경계로 구분할 수 있었다. 다만 현장적용을 위해서는 침목의 영향을 분리하고 전자기파 분산특성 등에 대한 추가 연구가 필요할 것으로 사료된다.

Keywords

References

  1. Al-Qadi, I. L., Xie, W. and Roberts, R. (2008), Scattering analysis of ground-penetrating radar data to quantify railroad ballast contamination, NDT&E International, Vol. 41, No. 6, pp. 441-447. https://doi.org/10.1016/j.ndteint.2008.03.004
  2. Clark, M. R., Gillespie, R., Kemp, T., McCann, D. M. and Forde, M. C. (2001), Electromagnetic properties of railway ballast, NDT&E International, Vol. 34, No. 5., pp. 305-311. https://doi.org/10.1016/S0963-8695(00)00006-2
  3. Davis, J. L. and Annan, A. P. (1989), Ground-penetrating radar for high-resolution mapping of soil and rock stratigraphy, Geophysical Prospecting, Vol. 37, No. 5.
  4. GSSI SIR-30 (2015), http://www.geophysical.com/sir30.htm
  5. Hyslip, J., Smith, S., Olhoeft, G. and Selig, E. T. (2003), Assessment of railway track substructure condition using ground penetrating radar, Proceedings of the 2003 Annual Conference of AREMA, Chicago, Illinois, USA, Expanded Abstracts.
  6. Jeong, J. D., Lee, J. H., Choi, M. J., Lee, J. S. and Jung, J. J. (2015), Survey of the Road Cave-in using Ground Coupled GPR, KSCE 2015 CONVENTION 2015 CIVIL EXPO & CONFERNCE, 2015.10, pp. 115-116.
  7. Jol, H. M. (2009), Ground penetrating radar theory and applications, Elsevier, pp. 141-147, ISBN 978-0-444-53348-7.
  8. Kim, D. S., Kwon, S. S., Lee, S. H., Hwang, S. K. and Park, T. S. (2008), Study on the appropriateness of track maintenance works through the evaluation of trackbed conditions, Journal of the Korean Society for Railway, Vol. 11, No. 3, pp. 334-341 (in Korean).
  9. Kim, Y. E. (2000), Structural condition assessment of reinforced concrete structures using GPR, KCI concrete journal, Vol. 12, Vol. 3, pp. 78-84.
  10. KORAIL (2015), http://info.korail.com/mbs/www/jsp/board/list.jsp?boardId=9863289&id=www_060702000000
  11. Leng, Z. and Al-Qadi, I. L. (2010), Railroad ballast evaluation using ground-penetrating radar, Transportation Research Record : Journal of the Transportation Research Board, Vol. 2159, No. 1, pp. 110-117. https://doi.org/10.3141/2159-14
  12. Leucci, G. (2008), Ground Penetrating Radar: The Electromagnetic Signal Attenuation and Maximun Penetrating Depth, Scholarly Research Exchange, Vol. 2008, doi:10.3814/2008/926091.
  13. Olhoeft, G. R. (2000) Maximizing the information return from ground penetrating radar, Journal of Applied Geophysics, Vol. 43, No. 2, pp. 175-187. https://doi.org/10.1016/S0926-9851(99)00057-9
  14. Roberts, R., Al-Qadi I., Tutumluer E., Boyle J. and Rudy J. (2006), Railroad Ballast Fouling Detection Using Ground Penetrating Radar - A New Approach Based on Scattering from Voids, ECNDT 2006, September 25-29, Berlin, Germany, pp. 8.
  15. Yoo, K. C., Han, Y, S. and Kee, J. S. (2015), A study on the technology quality of GPR for underground cavern exploration, KSCE 2015 CONVENTION 2015 CIVIL EXPO & CONFERNCE, 2015.10, pp. 39-40.
  16. Selig, E. T. and Waters J. M. (1994), Track geotechnology and substructure management, Thomas Telford, London.
  17. Zhang, Y., Venkatachalam, S. A., Xie, Y., Wang, G. and Xia, T. (2014), Data analysis technique to leverage ground penetrating radar ballast inspection performance, IEEE National Radar Conference paper, doi:10.1109/RADAR.2014.6875636.