Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
권호 표지
DOI QR코드

DOI QR Code

Experimental analysis on the channel adjustment processes by weir removal

실내실험에 의한 기능을 상실한 보 철거로 인한 하도의 적응과정 분석

  • Jang, Chang-Lae (Department of Civil Engineering, Korea National University of Transportation) ;
  • Lee, Kyung Su (National Disaster Management Institute, Ministry of the Interior and Safety)
  • 장창래 (한국교통대학교 토목공학과) ;
  • 이경수 (행정안전부 국립재난안전연구원)
  • Received : 2020.04.27
  • Accepted : 2020.09.13
  • Published : 2020.11.30
Download PDF
⟨ Previous Next ⟩

Abstract

This study investigates the adjustment processes of the rivers after weir removal through laboratory experiments. Delta upstream eroded rapidly by flow at the initial stage of the experiments and the knickpoint migrates upward. Moreover, the knickpoint moves fast upward on the condition of alternate bars. The head cutting in the bed is developed fast at the initial stage. However, the erosion speed in the bed decreases with time. The well developed alternate bars migrates with keeping their shape downstream, and the bars affect the channel downstream to adjust new environments after weir removal. Maximum scouring depth downstream and the migration speed decrease over time after removing the weir. The scouring depth in the channel without alternate bars migrates with speed. However, the depth in the channel with alternate bars migrates slow downstream. The channel with alternate bars, in turn, is adjusted well to the new equilibrium states. The maximum scouring depth migrates downstream with time, and the scouring depth and its migration speed decreases with time. The dimensionless maximum scouring depth decreases with the migration speed of dimensionless maximum scouring depth because the deeply scoured places capture the sediments from upstream and the migration speed is slow as the places are filled with them. The dimensionless maximum scouring depth is shallow as the dimensionless backfilling speed is high. The dimensionless maximum scouring depth decreases rapidly less than 5 of dimensionless backfilling speed. However, the depth decreases slow more than 5 of it.

본 연구에서는 실내실험을 통하여 기능을 상실한 보 철거로 인하여, 급경사가 형성된 짧은 구간에서 두부침식과 천급점 변화, 그리고 교호사주의 거동을 고려한 하도의 적응과정을 정량적으로 분석하였다. 보 상류에서 두부침식이 발생하여 천급점은 상류로 이동하였다. 실험초기에 빠르게 이동하지만, 시간이 증가하면서 이동속도가 감소하였다. 교호사주가 발달한 조건에서 이동속도는 사주가 발생하지 않은 조건에서보다 빨랐다. 세굴심은 교호사주가 발생하지 않는 조건에서 보다 발생하는 조건에서 더 깊었다. 시간이 증가할수록 최대세굴심은 하류로 이동하며, 최대세굴심의 깊이와 이동속도는 감소하였다. 무차원 최대세굴심은 상류에서 유입되는 유사가 포착되고 되메우기가 진행되면서 이동속도가 감소하였다. 무차원 되메우기 속도가 증가할수록 무차원 최대세굴심은 감소하였다. 초기에 최대세굴심이 깊은 곳에서 되메우기가 빠르게 진행되며, 최대세굴심이 얕은 곳에서는 되메우기가 느리게 진행되었다. 특히, 무차원 되메우기 속도가 5이하에서는 무차원 최대세굴심이 급격하게 감소하며, 그 이후에서는 완만하게 감소하였다.

Keywords

References

  1. Bhallamudi, S.M., and Chaudhry, M.H. (1991). "Numerical modeling of aggradation and degradation in alluvial channels." Journal of Hydraulic Engineering, ASCE, Vol. 117, No. 9, pp. 1145-1164. https://doi.org/10.1061/(ASCE)0733-9429(1991)117:9(1145)
  2. Brush, L., and Wolman, M. (1960). "Knickpoint behavior in noncohesive material: A laboratory study." Bulletin of the Geological Society of America, Vol. 71, pp. 59-71. https://doi.org/10.1130/0016-7606(1960)71[59:KBINMA]2.0.CO;2
  3. Cantelli, A., Paola, C., and Parker, G. (2004). "Experiments on upstream-migrating erosional narrowing and widenging of an incisional channel caused by dam removal." Water Resources Research, Vol. 40, W03304, doi:10.1029/2003WR002940.
  4. Cui, Y., Braudrick, C., Dietrich, W., Cluer, B., and Parker, G. (2006b). "Dam removal express assessment models (DREAM). Part 2: Sample runs/sensitivity tests." Journal of Hydraulic Research, Vol. 44, No. 3. pp. 308-323. https://doi.org/10.1080/00221686.2006.9521684
  5. Cui, Y., Parker, G., Braudrick, C., Dietrich, W., and Cluer, B. (2006a). "Dam removal express assessment models (DREAM). Part 1: Model development and validation." Journal of Hydraulic Research, Vol. 44, No. 3. pp. 291-307. https://doi.org/10.1080/00221686.2006.9521683
  6. Cui, Y., and Wilcox, A. (2008). "Development and application of numerical models of sediment transport associated with dam removal." Sedimentation engineering: Theory, measurements, modeling, and practice, ASCE manual 110, Edited by Garcia, M.H., 995-1020, ASCE, Reston, VA, U.S.
  7. Jang, C.-L. (2012). "2-Dimensional numerical simulation of the behaviors of knickpoint in the channel with noncohesive materials." Journal of Korean Society of Hazard Mitigation, Vol. 12, No. 6, pp. 259-265 (in Korean). https://doi.org/10.9798/KOSHAM.2012.12.6.259
  8. Jang, C.-L., and Jung, K.S. (2010). "Experimental study on the ad justment processes of minning pit in the dredged channels." Journal of Korea Water Resources Association, KWRA, Vol. 43, No.7, pp. 657-666, doi: 10.3741/JKWRA.2010.43.7.657 (in Korean).
  9. Jang, C.-L., and Shimizu, Y. (2010). "Numerical simulation of sand bars downstream of Andong Dam." Journal of The Korean Society of Civil Engineers, Vol. 30, No. 4B, pp. 379-388.
  10. Korea Institute of Construction Technology (KICT) (2008). The stream eco-corridor restoration and water quality improvement by weir removal with its function lost.
  11. Lee, K.S., Jang, C.-L., and Kim, G.J. (2019). "Experimental analysis of geomorphic changes in weir downstream by behavior of alternate bar upstream." Journal of Korea Water Resources Association, KWRA, Vol. 52, No. S-2, pp. 801-810.