Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Effect of Wave-Induced Seepage on the Stability of the Rubble Mound Breakwater

동적 파랑에 의한 침투류가 사석경사식 방파구조물의 안정성에 미치는 영향

  • Hwang, Woong-Ki (Dept. of Civil Engrg., Korea Maritime and Ocean Univ.) ;
  • Kim, Tae-Hyung (Dept. of Civil Engrg., Korea Maritime and Ocean Univ.) ;
  • Kim, Do-Sam (Dept. of Civil Engrg., Korea Maritime and Ocean Univ.) ;
  • Oh, Myounghak (Coastal Disaster Prevention Research Center, Korea Institution of Ocean Science & Technology) ;
  • Park, Jun-Young (Dept. of Geotechnical Engrg., Hyein Engineering & Construction)
  • 황웅기 (한국해양대학교 건설공학과) ;
  • 김태형 (한국해양대학교 건설공학과) ;
  • 김도삼 (한국해양대학교 건설공학과) ;
  • 오명학 (한국해양과학기술원 연안방재연구센터) ;
  • 박준영 ((주)혜인이엔씨 지반부)
  • Received : 2017.11.06
  • Accepted : 2018.02.25
  • Published : 2018.03.31
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Abstract

To study how stable the rubble mound breakwaters are, one can look to the research of wave induced seepage flow through the pores of the rubble mound. Seepage flow is generally generated by the difference between the water level around the breakwater during a typhoon. The existing stability analysis method of the rubble mound is the static analysis which simply considers the force equilibrium taking into account the horizontal force acting on the concrete block induced by a wave (calculated by Goda equation) and the vertical force induced by the weight inclusive of the concrete block, quarry run, filter, and armor layer above the slipping plane. However, this static method does not consider the wave-induced seepage flow in the rubble mound. Such seepage may decrease the stability of the rubble mound. The stability of a rubble mound breakwater under the action of seepage was studied based on the results of CFD software (OpenFOAM) and Limit Equilibrium Method (GeoStudio). The numerical analysis result showed that the seepage flow decreased the stability of the rubble mound breakwaters. The results of the numerical analyses also revealed the stability of the rubble mound was varied with time. Especially, the most critical state happened at the condition of overtopping the concrete block, acting strong uplift pressure raising along side and underneath the concrete block, and generating high pore pressure inside rubble mound due to seepage flow. Therefore, it may be necessary to conduct a dynamic analysis considering the effect of wave-induce seepage flow together with the static analysis.

사석경사식 방파제의 안정성에 있어 파랑에 의한 사석마운드내의 침투흐름의 영향이 연구되었다. 침투흐름은 일반적으로 태풍시 방파제 주변 수위차에 의해 발생된다. 기존 사석마운드의 안정해석법은 정적해석으로 활동면 상의자중(콘크리트블록, 사석, 필터, 보호층)에 의한 수직력과 콘크리트 블록에 작용하는 파압에 의한 수평력(Goda 식으로 산정)의 힘의 평형조건으로 결정된다. 그러나 이 정적방법은 사석마운드 내의 파랑에 의한 침투흐름을 고려할 수 없다. 이런 침투흐름은 사석마운드의 안정성을 감소시킬 수 있다. 본 연구에서는 침투 작용시 사석경사식 방파제의 안정성에 대해 CFD 프로그램(OpenFOAM)과 한계평형해석법(GeoStudio)을 이용하여 검토하였다. 수치해석결과 침투로 인해 사석경사식 방파제의 안정성이 감소하는 것으로 나타났다. 또한 수치해석 결과는 사석마운드의 안정성이 시간에 따라 변하는 것을 보여주었다. 특히 파가 방파제를 월류하고 침투류에 의해 상치콘크리트 측면과 하부에 강한 양압력과 사석마운드 내부에 간극수압이 크게 발생하는 시점에 가장 불안정 상태를 보이는 것으로 나타났다. 따라서 동적 파랑에 의한 침투류의 영향을 고려한 동적해석도 정적해석과 함께 검토할 필요가 있다.

Keywords

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