• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.4
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• pp.214-223
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• 2003

A reliability analysis is straightforwardly applied to the sloped coastal structures against the random wave overtopping. A reliability function can be directly derived from a empirical formula in which may take into account many variables associated with the random wave overtopping. The probability of failure exceeded the allowable overtopping discharge can be evaluated as a function of dimensionless crest height with some reasonable statistical properties and distribution functions of each random variable. Some differences of probabilities of failure occurred from variations of the slopes of structures as well as types of armour are investigated into quantitatively. Additionally, the effects of the crest width of units placed in front of the concrete cap on the probability of failure may be analyzed. Finally, the sensitivity analyses are carried out with respect to the uncertainties of random variables. It is found that the overall characteristics similar to the known experimental results are correctly represented in this reliability analyses. Also, it should be noted that the probabilities of failure may be quantitatively obtained for several structural and hydraulic conditions, which never assess in the deterministic design method. Thus, it may be possible for determination on the crest height of sloped coastal structures to consider the probability of failure of wave overtopping, by which may be increased the efficiency of practical design.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.326-334
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• 2017

We obtain height of waves overtopping on a porous breakwater using both the one-layer and two-layer Boussinesq equations. The one-layer Boussinesq equations of Lee et al. (2014) are used and the two-layer Boussinesq equations are derived following Cruz et al. (1997). For solitary waves overtopping on a porous breakwater, we find through numerical experiments that the height of waves overtopping on a low-crested breakwater (obtained by the Navier-Stokes equations) are smaller than the height of waves passing through a high-crest breakwater (obtained by the one-layer Boussinesq equations) and larger than the height of waves passing through a submerged breakwater (obtained by the two-layer Boussinesq equations). As the wave nonlinearity becomes smaller or the porous breakwater width becomes narrower, the heights of transmitting waves obtained by the one-layer and two-layer Boussinesq equations become closer to the height of overtopping waves obtained by the Navier-Stokes equations.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.1
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• pp.1-10
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• 2013

In this study, impact vibration tests are applied to analyze the vibration characteristics of caisson-type breakwater, and the results obtained from vibration tests are compared with numerical simulation results considering fluid-soil-structure interaction effects to verify the feasibility of a numerical analysis model. It is found that natural frequencies are reduced as amount of 1.7-4.3% after additional parapet structure is added to increase the height of breakwater, and the same results was observed from the numerical simulation study. Through the comparison, it was verified that the vibration tests and numerical simulation study can be applied to evaluate the vibration characteristics of caisson-type breakwater.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.623-631
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• 2003

A large scale hydrological laboratory model tests for the geotextile tube were conducted to investigate the stability of geotextile tube and the capability of breakwater with variations of significant wave height, percentage of soil filling, and the water level above geotextile tube. The sliding displacement of geotextile tube is measured to check the stability of geotextile tube for given the various significant wane heights. The marked mash was laid out at the bottom of water channel to measure the displacement of geotextile tube. The bench mark was furnished in the upper part of water channel and the initial location was marked every 10cm interval to measure the displacement of geotextile tube. The wane transmit ratios are analyzed with the variations of soil filling of tube and of the top crown height wave above the geotextile tube in order to study the performance of brekwater before and after the installation of geotextile tube.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.2
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• pp.41-49
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• 2019

We approximately obtain heights of cnoidal waves overtopping on a porous breakwater using both the one-layer Boussinesq equations (Vu et al., 2018) and the two-layer Boussinesq equations (Huynh et al., 2017). For cnoidal waves overtopping on a porous breakwater, we find through numerical experiments that the heights of cnoidal waves overtopping on a low-crested breakwater (obtained by the Navier-Stokes equations) are smaller than the heights of waves passing through a high-crested breakwater (obtained by the one-layer Boussinesq equations) and larger than the heights of waves passing through a submerged breakwater (obtained by the two-layer Boussinesq equations). As the cnoidal wave nonlinearity becomes smaller or the porous breakwater width becomes narrower, the heights of transmitting waves obtained by the one-layer and two-layer Boussinesq equations become closer to the height of overtopping waves obtained by the Navier-Stokes equations.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.57-65
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• 2005

Geotextile have been used for the past 30 years for various types of containers, such as small sandbag, 3-D fabric forms and aggregate filled gabion etc. While they are mainly used for flood and water control, they are also used against beach erosion fir shore protection. Especially, large-sized geotextile tube structures are used in various innovative coastal systems involving breakwaters. This paper presents the hydrodynamic behavior of geotextile tubes based on the results of hydraulic model tests. These tube are generally about 1.0 m to 2.0 m in diameter, thou띤 they can be sized for any application. The tubes can be used solely, or stacked to add greater height and usability. Stacked geotextile tubes will be created by adding the height necessary for some breakwaters and embankment, therefore increasing the usability of geotextile tubes. The hydraulic model test was conducted as structural condition and wave conditions. Structural condition is installation direction to the wave (perpendicular and 45$^{circ}$$), and wave condition is varied with the significant wave height ranging from 3.0 m to 6.0 m. Compared with previous test result, the stacked geotextile tube is more stable against wave attack than single tube. Also, the case of none-water depth above crest is more stable than 0.5H of water depth above crest. The incline installed stacked tube is more effective for wave adsorption.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.482-488
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• 2011

Seadike is a coastal structure constructed in the rear region of the foreshore to maximize its usability by preventing direct effect of wave. The expected construction field is determined under the design wave and tidal condition where minor wave overtopping is anticipated. Thus, the location of seadike is generally fixed at the highest site of the surrounding area with seadike crest height controlling the permissible range of wave overtopping volume. But a lot of times, frontal sand beach of the seadike continuously deforms due to incident waves, resulting failure in maintaining its initial slope. The erosion and deposition of the seadike front cause changes in the crest height and volume of wave overtopping and decrease in the setting depth of the seadike, which endangers seadike region as a result. In this study, the relation of local scouring and setting depth of the seadike front in the run-up region is examined by using 2D hydraulic model tests and numerical simulations by modified SBEACH model. As a result, the study learned that if appropriate boundary condition is applied to the modified SBEACH model, it is possible to create practical estimations on the local scouring at the seadike foot when erosive waves flow into the region.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.203-214
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• 2010

This study numerically investigates the wave control of 2-rowed Impermeable Rectangular Submerged Dike(IRSD) with an object of how to control short-period and solitary waves simultaneously based on the Bragg resonance phenomenon that elevates the wave control performance. The boundary integral method using Green formula and the 3-D one-field Model for immiscible TWO-Phase flows (TWOPM-3D) by 3-D numerical wave flume have been used for the numerical predictions for short-period and solitary waves, respectively. These numerical models were verified through the comparisons with the previously published numerical results by other researchers. Through the parametric tests of numerical experiments for short-period waves, an optimum model of 2-rowed IRSD of a lowest transmission coefficient has been found. Furthermore, the performances of 3-D wave control for solitary waves were evaluated for the various free board, crown widths and gap distance between dikes, and have been compared with those of a single-rowed IRSD. Numerical results show that a 2-rowed IRSD with a less cross sectional area than 1-rowed one improves the wave attenuation performances when it is compared to that of single-rowed IRSD. Within the test frequency ranges of the numerical simulations conducted in this study, 2-rowed IRSD with an optimum gap distance shows an outstanding improvement of the wave attenuation up to 58% compared to that of single-rowed IRSD.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.2
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• pp.176-183
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• 2008

In this paper, three classical overtopping models: Owen model, Van der Meer & Janssen model and Hedges & Reis model were used to calculate the failure probability of wave overtopping of seawalls. Among of them, the Hedges & Reis model was regarded as a moderate method to analyze the failure probability of wave overtopping of seawalls and the probabilistic assessments of wave overtopping were carried out for a constructing seawall at Busan in Korea by Level II and Level III reliability methods. Considering the cost of construction, an appropriate crest level was proposed for a certain rate of wave overtopping at a lower failure probability.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.219-219
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• 2022

지구 온난화와 함께 발생하는 해수면 상승은 한반도의 해안지역을 비롯하여 울릉도 등 도서지역 전반에 걸쳐 진행 중이다. 또한 해수면의 온도 상승으로 인한 열대저기압의 생성 시 에너지 공급이 증가하며 연안으로 내습하는 파랑 내습 에너지가 커지게 된다. 경상북도 울릉군에 위치한 남양항은 최근 2019년 태풍 다나스 및 2020년 태풍 마이삭 등에 의해 고파랑 혹은 침수 피해가 발생하여 항 내에서는 물양장과 선박이 파괴되고 방파제가 전도되는 등의 피해가 속출하였다. 동해안의 태풍 내습, 지구 온난화와 저기압 발달에 의한 수위 상승 등과 같은 다양한 해양기후를 고려한 연안 구조물의 파랑 영향을 검토하는 것이 중요할 것으로 판단되었다. 기상청 태풍센터에서 제공하는 1979년부터 2020년까지 한반도 해역에 내습한 태풍 중 울릉도에 영향을 미친 태풍은 18개로 울릉도 인근에 영향을 준 내습 태풍을 10년 단위로 분석해 보면, 1980년대 3개, 1990년대 2개, 2000년대 8개, 2010년대 3개, 2020년 2개로 2000년대에 울릉도 영향권에 들어간 태풍이 가장 많았으며, 심해파 추산 기간 이후 2020년 1년 동안 울릉도 인근으로 마이삭, 하이선과 같은 2개의 태풍이 연속적으로 영향을 주었다. 울릉도에 영향을 미친 18개 태풍을 대상으로 일본 기상청(JMA)에서 제공하는 1시간 바람장을 이용하여 파랑 후측 수치 모의를 수행하였으며, 해양수산부와 기상청 관측 부이를 이용하여 파랑에 대한 정확도를 확보하였다. 고파랑 내습 시 연안에 조우하는 수위 조건은 파랑 에너지의 증가를 결정하게 되며, 항만 구조물의 설계에 적용되고 있는 약최고고조위 이상(4대분조의 최대 조위)의 최극조위 조건에서 해안 구조물에 월파 및 침수 피해를 주는 요인으로 작용할 수 있다. 이를 바탕으로 울릉도 남양항에서 폭풍 시 내습한 최극고조위(0.65m)와 IPCC 5차 보고서에 제시한 최악의 시나리오(RCP 8.5) 조건에서 울릉도에서 확인된 0.79 cm 상승고를 반영하여 범람위험평가를 광역에서의 계산 결과를 입력자료로 하여 준 3차원 비 정수압 파랑 변형 수치 모형인 MIKE 3 Wave를 사용하여 실험하였다. 해수면 상승에 의한 수위 상승고는 연안 파랑 증가에 영향을 주었으며 연안 구조물의 침수 피해에 영향을 줄 것으로 판단되었다. 월파 차단, 파랑 차폐의 목적으로 건설되는 구조물의 규모 및 천단고 등을 설정하는데 설계 수위의 선정은 중요하다. 수치 실험 결과를 바탕으로 방파제 및 호안의 범람 위험 평가를 수행하고 구조물 설계 시 이러한 해수면 상승고가 반영된 설계가 중요하다는 것을 위험 평가를 통해 확인할 수 있다.