DOI QR코드

DOI QR Code

Experimental Study on Mechanism Analysis of Headcut Erosion in the Noncohesive Sediment Bed

비점착성 하상에서의 두부침식 메커니즘 분석에 관한 실험 연구

  • Ji, Un (Hydro Science and Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology) ;
  • Jang, Eun-Kyung (Hydro Science and Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology) ;
  • Kang, Jin-Wook (Hydro Science and Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology)
  • 지운 (한국건설기술연구원 수자원.하천연구소) ;
  • 장은경 (한국건설기술연구원 수자원.하천연구소) ;
  • 강진욱 (한국건설기술연구원 수자원.하천연구소)
  • Received : 2014.09.12
  • Accepted : 2015.02.12
  • Published : 2015.02.28

Abstract

The headcut erosion at the confluence section of a mainstream and tributary can migrate up the tributary streams, and rapid degradation can threaten the stability of hydraulic structures installed in the channel. Therefore, quantitative analysis for the development and mechanism of headcut erosion is needed to prevent damage due to the headcut. In this study, hydraulic experiments for headcut erosion in the channel with noncohesive materials were performed and the knickpoint movement and final bed slope change were analyzed based on the different hydraulic conditions. As a result, the knickpoint movement was 1.5 times faster when the difference in velocity between the upstream and downstream sections was 2.5 times greater and the central part of the cross-section was eroded and collapsed earlier than the left and right sides. The movement length of headcut erosion was longer and the final bed slope was milder as the velocity difference between the upstream and downstream sections was increased. This study showed that a correlation between the knickpoint movement and bed slope change by headcut erosion and the water level difference of upstream and downstream sections was not constant compared to the velocity difference.

하천의 본류와 지류가 만나는 합류부 구간에서 시작된 두부침식은 시간에 따라 지류 상류로 전파될 수 있으며, 급격한 하상저하로 인해 지류에 설치된 수리구조물의 안정성을 위협할 수 있다. 이러한 두부침식의 피해를 사전에 방지하기 위해서는 발생원인과 그 메커니즘에 대한 정량적 분석이 반드시 필요하다. 따라서 본 논문에서는 개수로 실험 장치를 이용하여 비점착성 유사로 이루어진 하상에서의 두부침식에 관한 수리실험을 수행하였으며, 수리 조건에 따른 천급점 이동 및 최종 하상경사 변화 등을 분석하였다. 분석 결과, 상하류단의 유속차가 2.5배 큰 조건에서 천급점 이동이 약 1.5배 더 빠르게 진행되는 것으로 나타났으며 좌안과 우안에 비해 중앙의 침식 및 붕괴가 먼저 발생하는 것으로 나타났다. 또한 상 하류단 유속차가 클수록 두부침식 이동길이가 길어지고 더 완만한 하상경사가 나타나는 것을 확인하였으며 본 실험에서는 수위차의 경우 유속차에 비해 상대적으로 두부침식 이동성 및 하상경사에 미치는 상관관계가 일정하지 않는 것으로 나타났다.

Keywords

References

  1. The Kyunghyang Shinmun, "Head cutting of geumdang stream, because 4-river project not flood." August 12, 2011.
  2. N. J. Lee, K. I. Son, K. K. Yu, "Headcutting Fieldstudy of Byeongseongstream, Gamstream, HwangRiver.", Magazine of Korea water resources association, Vol. 44, No. 7, pp. 64-71, 2011.
  3. O. R. Stein, P. Y. Julien, "Criterion Delineating the Mode of Headcut Migration.", Journal of Hydraulic Engineering, Vol. 119, No. 1, pp. 37-50, 1993. DOI:http://dx.doi.org/10.1061/(ASCE)0733-9429(1993) 119:1(37)
  4. L. M. Brush, M. G. Wolman, "Knickpoint behavior in noncohesive material: a laboratory study.", Bulletin of the Geological Society of America, Vol. 71, pp. 59-71, 1960. DOI: http://dx.doi.org/10.1130/0016-7606(1960)71[59:KBINMA]2.0.CO;2
  5. S. J. Bennett, C. V. Alonso, S. N. Prasad, M. J. M. Romkens, "Experiments on headcut growth and migration in concentrated flows typical of upland areas.", Water Resources, Vol. 37, No. 7, pp. 1911-1922, 2000. DOI: http://dx.doi.org/10.1029/2000WR900067
  6. S. M. Bhallamudi, M. H. Chaudhry, "Numerical Modeling of Aggradation and Degradation in Alluvial Channels.", Journal of Hydraulic Engineering, Vol. 117, No. 9, pp. 1145-1164, 1991. DOI: http://dx.doi.org/10.1061/(ASCE)0733-9429(1991)117:9(1145)
  7. C. L. Jang, "2-Dimensional Numerical Simulation of the Behaviors of Knickpoint in the Channel with Noncohesive Materials.", Journal of the Korean Society of Hazard Mitigation, Vol. 12, No. 6, pp. 259-265, 2012. DOI: http://dx.doi.org/10.9798/KOSHAM.2012.12.6.259
  8. H. S. Woo, River Hydraulics, 2001.
  9. V. T. Chow, Open-Channel Hydraulics, Mc-Graw Hill, New York, USA, p. 25, 1959.