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2025 Vol.30, Issue 2

Article

Development of Tidal-Induced Local Scour Around Offshore Structure: A Case Study in Shinan Area

조석에 의한 해상 구조물 주변 국지세굴 발달 양상: 신안해역 사례

JI HEE OH1
,
BYEONG JIN JEON12
,
SEONG WOON JEONG1
,
JAE HYEOK SHIN1
,
INSUNG JEON3
,
HO KYUNG HA4*
오 지희1
,
전 병진12
,
정 성운1
,
신 재혁1
,
전 인성3
,
하 호경4*
1Graduate Student, Department of Ocean Sciences, Inha University, Incheon 22212, Korea
2Associate, Korea Hydrography and Research Association, Seoul 08590, Korea
3Principal Researcher, Korea Electric Power Research Institute, Daejeon 34056, Korea
4Professor, Department of Ocean Sciences, Inha University, Incheon 22212, Korea
1인하대학교 해양과학과 대학원생
2한국해양조사협회 사원
3한국전력공사 전력연구원 책임연구원
4인하대학교 해양과학과 교수
*Corresponding Author
31 May 2025. pp. 81-92
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Abstract

Local scour is a geomorphological process around offshore structures and directly affects their structural stability. In tidal-dominated regions, in particular, the tidal asymmetry can induce directional bias in the development of local scour. In order to investigate the development characteristics of local scour under tidal forcings, a rotary sonar profiler was installed on a jacket-type offshore platform located within the Shinan Offshore Wind Farm, Jeollanam-do for 22 days from April 18 to May 9, 2024. The in-situ mooring observations revealed the formation of an asymmetric local scour with deeper scour depth in the ebb direction because of an ebb-dominant tidal asymmetry. On average, the scour depth in the ebb direction (1.83 m) was approximately 31.6% deeper than that in the flood direction (1.39 m). The maximum scour depth reached 3.11 and 3.03 m during the spring and neap tides, respectively. Although the maximum scour depth varied during the mooring period, it remained consistently around 2.85 m, indicating the local scour had generally reached a stabilization state, despite short-term fluctuations by tidal variations. The scour slopes in the ebb (<26°) and flood (<16°), referenced to the local seabed, were both lower than the typical angle of repose (~32°) commonly observed in tide-dominant environments. It is speculated that the repetitive cycles of erosion and redeposition contributed to the development of a relatively gentle and stable scour slope. Sediments eroded during the scour process were transported by tidal currents, and subsequently redeposited as a 0.5 m-high mound on the northwestern side of the structure. This study quantitatively elucidated the influence of tidal asymmetry on the local scour morphology and the structural stability around an offshore platform. Furthermore, the results could serve as baseline data for predicting and managing benthic morphological changes around offshore platforms.

Keywords
Local scour
Rotary sonar profiler
Offshore structure
Tidal asymmetry

국지세굴은 해상 구조물 주변에서 발생하는 해저 지형 변화로, 구조물의 안정성에 직접적인 영향을 미치는 중요한 현상이다. 특히, 조석 흐름이 지배적인 해역에서는 조류의 비대칭성으로 인해 세굴의 깊이와 형태가 특정 방향으로 발달하는 경향이 있다. 본 연구에서는 조석 주기에 따른 국지세굴의 발달 양상을 파악하기 위해, 전라남도 신안 해상풍력단지 내 자켓형 해상 플랫폼에 회전식 소나 프로파일러(rotary sonar profiler)를 설치하고, 2024년 4월 18일부터 5월 9일까지 총 22일간 현장 관측을 수행하였다. 관측 결과, 조석 방향을 따라 비대칭적인 국지세굴이 관측되었으며, 연구지역의 낙조 우세 비대칭형 조석으로 인해 낙조 방향에서 더 깊은 세굴 깊이가 확인되었다. 평균 세굴 깊이는 창조(1.39 m)보다 낙조(1.83 m) 방향에서 약 31.6% 더 깊었다. 최대 세굴 깊이는 대조기와 소조기에서 각각 3.11과 3.03 m까지 도달하였다. 최대 세굴 깊이는 지속적으로 증감하였으나, 평균적으로 2.85 m에서 안정적으로 유지되었다. 이는 국지세굴이 초기 및 발달 단계를 지나 점차 안정화되었으며, 조석에 기인한 단기적 변동이 존재함에도 불구하고 전체적으로는 안정화 상태에 도달했음을 시사한다. 세굴 경사는 바닥면을 기준으로 낙조(<26°)와 창조(<16°) 방향 모두에서 왕복성 조류가 지배적인 환경에서 일반적으로 관측되는 안식각(~32°)보다 작았으며, 이는 반복되는 퇴적물 침식과 재퇴적 과정으로 인해 경사면이 완만하게 유지된 것으로 해석된다. 세굴 과정에서 침식된 퇴적물은 구조물 주변의 조석에 의해 북서 방향 외곽에 약 0.5 m 높이로 재퇴적되었다. 본 연구는 조석의 비대칭성이 해상 플랫폼 주변의 국지세굴 형태와 구조물의 안정성에 미치는 영향을 정량적으로 규명하였다. 현장 관측 결과는 향후 해상 플랫폼 주변 해저 지형 변화를 예측하고 관리하는 데 유용한 기초자료로 활용될 수 있다.

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Information
  • Publisher :The Korean Society of Oceanography
  • Publisher(Ko) :한국해양학회
  • Journal Title :The Sea Journal of the Korean Society of Oceanography
  • Journal Title(Ko) :한국해양학회지 바다
  • Volume : 30
  • No :2
  • Pages :81-92
  • Received Date : 2025-04-17
  • Revised Date : 2025-05-20
  • Accepted Date : 2025-05-20
  • DOI :https://doi.org/10.7850/jkso.2025.30.2.081
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