• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.47-63
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• 2014

In this study theories of earth pressure such as Rankine, Coulomb, Trial Wedge, Improved Trial Wedge, used in the design for onshore and offshore structures, are analyzed and the characteristics of loaded pressure to virtual back (wall, plane) and wall surface in accordance with the structure type are suggested. To investigate characteristics of earth pressure, gravity retaining wall with inclined angle and cantilever wall with inclined ground are movilized for onshore structures and caisson and block type quay wall are mobilized for offshore structures. Based on various theories, the earth pressure applied angle(wall friction angle) and sliding angle toward the wall, which is influenced by the heel length, are calculated and compared. In the case of long heel, the pressure by Rankine's method in virtual plane and the mobilized angle are most reasonably estimated by the ground slope, and in the case of short heel, the pressure by Coulomb's method and the mobilized angle by the angle of wall friction. In addition, the sliding angle toward the wall estimated by the improved trial wedge method is large than the value of Rankine's method. Finally, in this study the reasonable method for calculating the pressure and the mobilized angle that can be applied to the routine design of port structures is proposed. The proposed method can decide the earth pressure with length of a heel and a self weight of retaining wall according to sliding angle toward the wall.

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.827-837
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• 2018

The stabilities of sliding and overturning of caisson and bearing capacity of mound against eccentric and inclined loads, which possibly happen to a composite caisson breakwaters, have been analyzed by using the technique of multiple failure modes. In deterministic approach, mathematical functions have been first derived from the ultimate limit state equations. Using those functions, the minimum cross section of caisson can straightforwardly be evaluated. By taking a look into some various deterministic analyses, it has been found that the conflict between failure modes can be occurred, such that the stability of bearing capacity of mound decreased as the stability of sliding increased. Therefore, the multiple failure modes for the composite caisson breakwaters should be taken into account simultaneously even in the process of deterministically evaluating the design cross section of caisson. Meanwhile, the reliability analyses on multiple failure modes have been implemented to the cross section determined by the sliding failure mode. It has been shown that the system failure probabilities of the composite breakwater are very behaved differently according to the variation of incident waves. The failure probabilities of system tend also to increase as the crest freeboards of caisson are heightening. The similar behaviors are taken place in cases that the water depths above mound are deepening. Finally, the results of the first-order modal are quite coincided with those of the second-order modal in all conditions of numerical tests performed in this paper. However, the second-order modal have had higher accuracy than the first-order modal. This is mainly due to that some correlations between failure modes can be properly incorporated in the second-order modal. Nevertheless, the first-order modal can also be easily used only when one of failure probabilities among multiple failure modes is extremely larger than others.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.53-53
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• 2011

최근에 세계화, 무역자유화에 따른 컨테이너 물동량이 증가하고 있다. 그에 발맞추어 초대형 컨테이너선이 등장하게 되고 신개념, 고효율의 항만인프라의 도입이 요구되고 있다. 이런 배경에 따라 최근에 국내외에서 부유식 안벽에 관한 기술 개발 및 연구가 더욱 필요한 상황이다. 부유식 안벽은 이동가능한 부유식 구조로 기존 항만의 확장 또는 신규 항만 건설시 환경문제를 최소화하고 기항, 선박수 및 선박의 크기에 따른 안벽 배열을 최적화 할 수 있어 항만 기능을 고도화함으로써 녹색항만을 구현하는데 많은 기여를 하게 될 것이다. 특히 컨테이너선의 양현하역과 환적이 가능하게 되어 컨테이너 터미널의 화물처리능력을 확대할 수 있을 뿐 아니라 기항선박의 체류시간을 최소화 할 수 있는 장점이 있다. 또한, 우리나라는 삼면이 바다로 크고 작은 항만들이 해안선을 따라 위치하고 있다. 이러한 항만들을 안전하게 보호하기 위한 방파제는 항만 기본시설인 외곽시설 중의 가장 중요한 구조물이다. 국내에 설치된 방파제는 대부분 사석이나 케이슨을 이용한 중력식 방파제로써 해저에 고정되어 해수면상으로 건설되므로 항내 외 해수교환을 차단하여 항내 수질악화를 초래할 뿐만 아니라 수심에 따라 막대한 건설비용이 소요된다. 따라서 친환경적이고 경제적인 새로운 형식의 방파제에 대한 연구 및 개발이 필요한 실정이다. 그 중 하나의 대안인 부유식 방파제는 공사기간이 짧고 비교적 수심에 대한 제약이 없는 것이 특징이다. 또한 해수의 원활한 흐름이 가능하기 때문에 중력식 방파제에 비해 경제적이며, 환경적 측면에서 큰 장점이 있다. 하지만 아직까지 부유식 방파제에 대한 국내 및 해외에서의 연구는 이론적인 해석을 중심으로 이루어져 부유식 방파제 실용화를 위한 많은 연구가 수행되어야 할 것으로 판단된다. 본 연구에서는 부유식 안벽 내에서 정온도를 효과적으로 유지하기 위하여 부유식 방파제를 설치하고 소파성능과 부유식 안벽내의 영향성을 수리모형실험을 통해 분석하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.716-716
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• 2012

최근 항만구조물을 설계함에 있어 대수심 및 고파랑 지역에 설치되는 외곽시설의 상당수는 직립식 케이슨 혼성제 단면을 채택하고 있다. 이는 상대적으로 수심이 깊고, 설계파와 같은 외력 조건이 크기 때문에 경사제에 비하여 경제성 및 시공성이 유리하기 때문으로 판단된다. 그렇지만 아직까지 소규모 항만 및 어항시설에 있어 경사제를 채택하고 있다. 본 연구에서는 이와 같은 경사식 구조물을 설계함에 있어 월파에 의한 방파제 배후 경사면에 피복된 피복재의 안정성을 검토하며, 실험사례를 통하여 최적 설계안 및 설계방향을 제시하고자 한다. 경사식 구조물 배후 사면 피복재의 안정 중량에 대해서는 우리나라의 항만 구조물의 설계기준(항만 및 어항설계기준, 2005) 뿐만 아니라 국외의 설계기준(CEM, Coastal engineering manual, 2005 등)에서도 아직까지 설계법을 제시하고 있지 않고 있다. 본 연구에서 수행한 단면 수리모형실험에서는 1/50의 실험축척을 적용하여 대상 외곽 구조물에 대하여 수리특성과 안정성을 검토하였다. 특히 경사제 배후의 안정성 확보를 위하려 동일 구간에 대하여 설계파 조건 등을 중심으로 총 9개의 실험안을 설정하여 안정성을 검토하였다. 아래 그림은 이중 초기 설계안과 최종적으로 제안된 제시안에 대한 완성모형, 실험장면 및 결과이다. 일반적으로 접안시설과 외곽시설이 어느 정도 이격되어 있어 적정량의 월파를 허용할 수 있는 경우 상치콘크리트의 형상 및 마루높이을 변경하여 월파의 낙하 및 도달거리를 배후면의 안정성을 확보할 수 있을 정도로 유도함으로써 안정적인 구조물 설계가 가능할 것으로 판단된다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.1
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• pp.54-62
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• 2009

The present study investigates the behaviour of overtopping flows falling on the leeside of a caisson breakwater with dissipating blocks through laboratory measurements. The falling overtopping flows in the leeside are expected to directly affect the leeside stability of the breakwater. This study focuses on not the resultant stability but the characteristic pattern of the overtopping flows depending on wave conditions through examining front velocity and plunging distance in the leeside. Regular waves were used to investigate the dependence of the overtopping flow pattern on wave conditions and a modified image velocimetry combining the shadowgraphy and cross-correlation method was employed for measurements of image and velocity. From the measurements, it is shown that the plunging distance and front velocity of the overtopping flow in the breakwater leeside increase as the wave period or height increases. From non-dimensional relationships between the variables, empirical formula for the velocity and overtopping distance are suggested.

• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.447-455
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction cf 9 new ports and renovation cf the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built cf steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions cf structures and increased underwater construction period. For the purpose cf cutting down the expense cf government budget, it is necessary to extend the life cycle of the existing structures. Therefore, we developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction of maintenance expenses and time for anti-corrosion work but also better protection This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.163-170
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction of 9 new ports and renovation of the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built of steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions of structures and increased underwater construction period. For the purpose of cutting down the expense of government budget, it is necessary to extend the life cycle of the existing structures. Therefore, we developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction maintenance expenses and time for anti-corrosion work but also better protection. This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.287-292
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• 2021

Load and resistance factor design is an efficient design approach that provides a system of consistent design solutions. This study aims to determine the load and resistance factors needed for the design of breakwater foundations within a probabilistic framework. In the study, four typical types of Korean breakwaters, namely, rubble mound breakwaters, vertical composite caisson breakwaters, perforated caisson breakwaters, and horizontal composite breakwaters, are investigated. The bearing capacity of breakwater foundations under wave loading conditions is thoroughly examined. Two levels of the target reliability index (RI) of 2.5 and 3.0 are selected to implement the load and resistance factors calibration using Monte Carlo simulations with 100,000 cycles. The normalized resistance factors are found to be lower for the higher target RI as expected. Their ranges are from 0.668 to 0.687 for the target RI of 2.5 and from 0.576 to 0.634 for the target RI of 3.0.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.3
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• pp.82-92
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• 2022

In recent years, coastal and port structures have attempted to prevent wave-overtopping or provide waterfront areas by installing superstructures on the structural crowns. In general, in the design stage, the Goda formula acting on the front the structure is applied to calculate the wave pressure acting on the superstructure in consideration of the wave-runup of the design wave. However, the wave pressure exceeding the Goda wave pressure could generate depending on the installation location of the superstructure where the wave-overtopping occurs. This study analyzed the applicability of the Goda formula to the wave pressure calculation for the superstructure of the vertical structures through hydraulic model experiments and numerical simulations. Furthermore, this study investigated the magnitude of the wave pressure acting on the superstructure based on detailed numerical results. As a result, the wave pressure acting on the superstructure was up to 120% higher than the maximum wave pressure on the still water surface. In addition, the wave pressure increases exponentially with the Froude number computed by the overtopping water depth at the crown of the structure, and we proposed an empirical formula for predicting the wave pressure based on the Froude number.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.183-186
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• 2011

해양구조물은 다양한 외력으로부터 지속적인 영향을 받으며 특히, 파력은 구조물의 설계에 결정적인 인자로 간주된다. 해양구조물 파장과 구조물의 크기와의 상대적인 관계로부터 크게 소형구조물, 대형구조물, 대상구조물로 대별될 수 있다. 전통적으로 소형구조물은 회절파의 발생이 없는 것으로 가정하여 Morison식으로부터 파력을 산정하고, 대형구조물은 회절파의 작용에 따른 관성력만을 고려하며, 대상구조물은 단면 2차원적인 파압만을 고려하여 Goda파압공식류로부터 작용파압을 추정하고 있다. 이러한 평가는 단주기파랑의 작용에 근거를 두고 있고, 또 대형 및 대상구조물의 경우에는 유체의 점성력을 고려하고 있지 않으며, 특히 지진해일파의 작용에 대한 평가는 전혀 이루어지지 않는 것이 현재의 상태이다. 본 연구는 대형구조물인 슬리트케이슨과 소형 구조물인 자켓구조물을 대상구조물로 선정하여 구조해석을 토대로 파랑의 변화에 따른 구조물의 거동특성을 연구하였다.