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

Korean Geo-Environmental Society (한국지반환경공학회)
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Development of Buried Type TDR Module for Leak Detection from Buried Pipe

매설관 주변부 누수 탐지를 위한 매설형 TDR 모듈 개발

  • Hong, Wontaek (Department of Civil & Environmental Engineering, Gachon University)
  • Received : 2021.10.12
  • Accepted : 2021.10.26
  • Published : 2021.11.01
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Abstract

To prevent accidents due to the cavities and loosened layers formed due to water leakage from the deteriorated buried pipes, evaluation of the changes in water contents around the buried pipes is required. As a method to evaluate the water contents of the soils, time domain reflectometry (TDR) system can be adopted. However, slender electrodes used in standard TDR probe may be damaged when buried in the ground. Thus, in this study, buried type TDR module was developed for the evaluation of the water contents with maintaining required shape of the electrodes in the ground. The TDR module is composed of three electrodes connected to the core conductor and outer conductor and a casing to prevent deformation and maintain alignment of the electrodes in the ground. For the verification of TDR waveforms measured using the TDR module, comparative analysis was conducted with the TDR waveforms measured using the standard TDR probe, and the relationship between the volumetric water content of the soils and the travel time of the guided electromagnetic wave was constructed. In addition, a model test was conducted to test the applicability of the buried type TDR module, and the experimental result shows that the TDR module clearly evaluates the changes in volumetric water contents due to the leakage from the modeled buried pipe. Therefore, the buried type TDR module may be effectively used for the health monitoring of the buried pipe and the evaluation of the water contents around the pipes buried in the urban pavements.

매설관으로부터의 누수에 의한 지반 내 공동 및 이완구간 형성에 따른 사고를 사전에 방지하기 위하여 매설관의 파손 및 누수와 동반한 지반 내 함수상태 변화의 평가가 요구된다. 흙의 함수상태 평가를 위한 기법으로써 시계열반사계(TDR)의 적용이 고려될 수 있으나 표준 TDR 프로브의 경우 세장비가 매우 큰 전극을 이용하므로 지반 내 설치 시 전극의 변형 및 파손이 발생할 수 있다. 본 연구에서는 지반 내에서 안정적으로 형태를 유지하며 함수상태를 평가할 수 있는 매립형 TDR 모듈을 개발하였다. 매립형 TDR 모듈은 동축케이블의 내부도체 및 외부도체에 연결되는 세 개의 전극과 지반 내에서 전극의 변형방지 및 평행배열 유지를 위한 MC Nylon 재질의 케이싱으로 구성된다. 매립형 TDR 모듈로부터 획득된 유도전자기파의 신뢰도 검증을 위하여 표준 TDR 프로브로부터 획득한 유도전자기파와 상호비교 하였으며 보정실험을 통하여 체적함수비와 유도전자기파의 전파시간 상관관계가 수립되었다. 매립형 TDR 모듈의 현장적용 적정성을 평가하기 위하여 실내 모형실험이 수행되었으며, 모형 매설관으로부터의 누수에 따른 흙 시료의 체적함수비 변화가 명확히 관찰되었다. 그러므로 본 연구에서 개발된 매립형 TDR 모듈은 도심지 포장 하부에 설치된 매설관의 건전도 평가 및 매설관 주변부 지반의 함수상태 평가에 효과적으로 이용될 수 있을 것이라 판단된다.

Keywords

Acknowledgement

본 연구는 국토교통부/국토교통과학기술진흥원의 지원으로 수행되었음(과제번호 21CTAP-C164270-01).

References

  1. ASTM D6565 (2005), Standard Test Method for Determination of Water (Moisture) Content of Soil by the Time-Domain Reflectometry (TDR) Method, ASTM International, West Conshohocken, PA, 2005.
  2. Benedetto, A. and Pensa, S. (2007), Indirect diagnosis of pavement structural damages using surface GPR reflection techniques, Journal of Applied Geophysics, Vol. 62, pp. 107~123. https://doi.org/10.1016/j.jappgeo.2006.09.001
  3. Brinkmann, R., Parise, M. and Dye, D. (2008), Sinkhole distribution in a rapidly developing urban environment: Hillsborough County, Tampa Bay area, Florida, Engineering Geology, Vol. 99, No. 3, pp. 169~184. https://doi.org/10.1016/j.enggeo.2007.11.020
  4. Diefenderfer, B., Galal, K. and Mokarem, D. W. (2005), Effect of subsurface drainage on the structural capacity of flexible pavement, VTRC 05-R35, Project, Vol. 66818, p. 29.
  5. Hyun, S. Y. (2016), Laboratory experiments of a ground-penetrating radar for detecting subsurface cavities in the vicinity of a buried pipe, The Journal of Korean Institute of Electromagnetic Engineering and Science, Vol. 27 No. 2, pp. 131~137. https://doi.org/10.5515/KJKIEES.2016.27.2.131
  6. Hyun, S. Y. (2017), A Study on characteristics of ground-penetrating radar signals for detection of buried pipes, The Journal of Korean Institute of Electromagnetic Engineering and Science, Vol. 28, No. 1, pp. 42~48. https://doi.org/10.5515/KJKIEES.2017.28.1.42
  7. Jung, J. and Lee, I. (2021), Image-based location tracking and mapping to improve accuracy of underground facility location information, Journal of the Korean Society of Civil Engineers, Vol. 69, No. 8, pp. 27~33.
  8. Kelly, E. J. (1999), Soil moisture effects in pavement systems, M. Sc. thesis, Ohio University, Athens.
  9. Kim, Y., Kim, J. B., Kim, D. and Han, J. G. (2017), Experimental study on generating mechanism of the ground subsidence of due to damaged waterssupply pipe, Journal of Korean Geosynthetics Society, Vol. 16, No. 2, pp. 139~148.
  10. Noborio, K., McInnes, K. J. and Heilman, J. L. (1996), Measurements of soil water content, heat capacity, and thermal conductivity with a single TDR probe, Soil Science, Vol. 161, No. 1, pp. 22~28. https://doi.org/10.1097/00010694-199601000-00004
  11. Subedi, S., Kawamoto, K., Karunarathna, A. K., Moldrup, P., Wollesen de Jonge, L. and Komatsu, T. (2013), Mini tensiometer-time domain reflectometry coil probe for measuring soil water retention properties, Soil Science Society of America Journal, Vol. 77, No. 5, pp. 1517~1528. https://doi.org/10.2136/sssaj2012.0106
  12. Topp, G. C., Davis, J. L. and Annan, A. P. (1980), Electromagnetic determination of soil water content: Measurements in coaxial transmission lines, Water Resources Research, Vol. 16. No. 3, pp. 574~582. https://doi.org/10.1029/WR016i003p00574
  13. Vaz, C. M. P. and Hopmans, J. W. (2001), Simultaneous measurement of soil penetration resistance and water content with a combined penetrometer-TDR moisture probe, Soil Science Society of America Journal, Vol. 65, No. 1, pp. 4~12. https://doi.org/10.2136/sssaj2001.6514
  14. Wang, P., Hu, Z., Zhao, Y. and Li, X. (2016), Experimental study of soil compaction effects on GPR signals, Journal of Applied Geophysics, Vol. 126, pp. 128~137. https://doi.org/10.1016/j.jappgeo.2016.01.019