• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.195-201
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• 2019

Long caisson breakwaters can improve the structural safety of a caisson due to the wave dispersion effect which reduces the average wave force acting on one caisson. However, in order to make long caissons, there are many manufacturing and construction limitations. Recently, interlocking caisson systems, which are to form a long caisson by interlocking individual caissons with adjacent caissons, have been much attention. In the present study, a interlocking caisson system with shear-keys was proposed and the wave dispersion effect according to the shear-key was evaluated analytically. As a result, (1) Because of the asymmetric shape of the interlocking caisson, the structure behavior and the wave dispersion effect of one are also asymmetric. (2) The wave dispersion effect is more influenced by the distribution and characteristics of wave acting on each caisson rather than the shape of the shear-key such as shear angle, height, shear length ratio. (3) The interlocking caisson breakwater is almost the same behavior and wave dispersion effect as a fully integrated breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.121-127
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• 2017

The actual wave is multi-direction irregular wave. In the case of a long structure, a reduction effect of the wave occurs. In this study, in order to grasp the extent to which these influences contribute to the failure probability and compare the existing modular breakwaters to the stability, we used existing modular breakwaters and long caisson breakwaters using wave force reduction parameter to analysis the reliability. As a result, the reliability index of the long caisson breakwater was higher than that of the existing modular caisson breakwater, and it was confirmed that the significant wave height of the design variables had the highest influence. In addition, the reliability analysis was performed according to the change of the mean value of the variables used in the calculation of the wave force reduction parameter. It is confirmed that the relationship between each variable value and the wave force reduction parameter appears in the analysis results.

• Journal of Korea Water Resources Association
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• v.43 no.10
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• pp.843-850
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• 2010

By employing multi-directional random waves, a parameter controlling the force acting on a long caisson breakwater is investigated in detail. Both JONSWAP (Joint North Sea Wave Project) and asymmetric directional spectra are adopted for frequency and directional spectra. It is found that the parameter decreases as the length of caisson and the angle of main direction of incident waves increase. Furthermore, the parameter is much similar to that of regular waves as the maximum spreading parameter $s_{max}$ increases. The parameter, however, decreases as asymmetry parameter ${\mu}$ increases when the main direction of incident waves is oblique to the breakwater.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.27-40
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• 2014

So far, studies on the settlement of breakwater have mainly been conducted through numerical model tests focusing on an analysis or through the laboratory wave tank tests using a scaled model. There has not been a study on the settlement that is measured in an actual breakwater structure. This study analyzed the data of settlement that has been measured in an actual caisson breakwater for a long time and the characteristics and causes of wave-induced settlement in the caisson (including beneath ground), based on qualitative aspect, were examined. The analysis revealed that wave clearly has an effect on the settlement in caisson, especially in the condition of high wave such as typhoon. Caisson settlement is caused by the liquefaction of ground, which is due to the increase of excess pore pressure, the combination of oscillatory excess pore pressure and residual excess pore water pressure, and the solidification process of ground due to dissipation of the accumulated excess pore pressure. The behavior of excess pore pressure in the ground beneath the caisson is entirely governed by the behavior of the caisson. Ground that has gone through solidification is not likely to go through liquefaction in a similar or a smaller wave condition and consequently, the possibility of settlement is reduced.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1258-1270
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• 2009

Recently, the earthquakes activities are more of frequency occurred in the country. In case of nomal or large magnitude earthquakes, which cause a rising number of life loss or widespread loss of property. It must be considered how to cope with the situperty of dpmage in the country ty account of ay earthquake. Consequently, the public works have currently ensured against a lot of risk about seismism not only on large scale structures but also relatively small structures. Therefore, in this study, in order to make the seismic stability safe, it has been evaluated by the seismic performance for caisson-type breakwater. The seismic response analyses have conducted on the caisson-type breaker under long-period, short-period and artificial seismic wave. The liquefaction potential of the foundation, which is caisson-type, is also estimated by using the simplified assessment method. Finally, the result of the numerical analysis by PENTAGON 2D finite element method(FEM) program are presented for 3 cases with time-history seismic analysis under the seismic load.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.77-82
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• 2017

Recently, the possibility of abnormal waves of which height is greater than design wave height have been increased due to the climate change, and therefore it has been urgent to secure the stability for harbor structures. As a countermeasure for improving the stability of conventional caisson breakwaters, a method has been proposed in which adjacent caissons are interlocked with each other to consecutively resist the abnormal wave forces. In order to reflect this research trend, the reduction effect of the maximum wave force resulted from introducing a long caisson has been presented in the revision to the design criteria for ports and fishing harbors and commentary. However, no method has been proposed to evaluate the stability of interlocking caisson breakwater. In this study, we consider the effect of the phase difference of the oblique incidence of the wave based on the linear wave theory and apply the Goda pressure formula for considering design wave pressure distribution in the vertical direction. Sliding stability assessment formula of an interlocking caisson breakwater is proposed for regular, irregular, and multi-directional irregular wave conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.113-127
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• 2007

In this study, a model to calculate the expected total construction cost is developed that simultaneously considers the rehabilitation cost related to the sliding of the caisson, the economic damage cost due to harbor shutdown in the event of excessive caisson sliding, and the economic damage cost due to temporal operational stoppage by excessive wave overtopping. A discount rate is used to convert the damage costs occurred at different times to the present value. The optimal cross-section of a caisson is defined as the cross-section that requires a minimum expected total construction cost within the allowable limit for the expected sliding distance of the caisson during the lifetime of the breakwater. Two values are used for the allowable limit: 0.3 and 0.1 m. It was found that the economic damage cost due to harbor shutdown by excessive caisson sliding is more critical than the rehabilitation cost of the caisson or the economic damage cost by excessive wave overtopping in the decision of the optimal cross-section. In addition, the optimal cross-section of the caisson was shown to be determined by the allowable limit for the expected sliding distance rather than the minimum expected total construction cost as a larger value is used for the threshold sliding distance of the caisson for harbor shutdown.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.66.2-66.2
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• 2010

장대 케이슨 방파제에 작용하는 다방향 불규칙파랑의 파력 평활화 계수를 계산하였다. 다방향 불규칙파랑의 주파수 스펙트럼으로는 Bretschneider-Mitsuyasu 스펙트럼을 사용하였고, 방향 스펙트럼은 Mitsuyasyu 타입의 스펙트럼을 적용하였다. 계산 결과 단일 케이슨의 길이가 길수록, 주파향의 입사각이 클수록 평활화 계수는 감소하였다. 다양한 에 대해서도 계산하였으며, 가 클수록 평활화계수는 규칙파와 비슷한 경향을 보였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.815-826
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• 2009

The paper presents a case study addressing the design and construction aspects for DCM(Deep Cement Mixing) method employed as the foundation of a caisson type breakwater with heavy weight(10,700 ton/EA) and a high design wave height($H_{1/3}$=8.7m). The DCM was designed for the project(Ulsan New Port North Breakwater Phase 1) by optimizing the pattern of DCM columns with a combination of short and long columns (i.e., block type(upper 3m)+wall type(lower)) and considering overlapped section between columns as a critical section against shear force where the coefficient of effective width of treated column($\alpha$) was estimated with caution. It was shown that the value can be 0.9 under the condition with the overlapped width of 30cm. In addition to that, a field trial test was performed after improving conventional DCM equipment (e.g., mixing blades, cement paste supplying pipes, multi auger motor, etc.) to establish a standardized DCM construction cycle (withdrawal rate of mixing blades) which can provide the prescribed strength. The result of the field strength test for cored DCM specimens shows that the averaged strength is larger than the target strength and the distribution of the strength(with a defect rate of 7%) also satisfies with the quality control normal distribution curve which allows defect rate of 15.9%.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.374-386
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• 2010

Recently, the theoretical and experimental research is being made actively in control character of waves of perforated-wall caisson breakwater like the slit caisson. This study showed that the character of reflection coefficient and the wave pressure acting on the front and inner of slit caisson were estimated in two and three dimensional numerical wave flume and compared each other. The numerical experiment was set and conducted by various cases as to a variety of wave steepness under 7 sec, 9 sec, 11sec and 13 sec period condition. In this study using a 2 and 3 dimensional numerical wave flume, it applied the Model for the immiscible two-phase flow based on the Naveir-Stokes Equations. This technique can easily reproduce a complicated physical phenomenon more than others and organize the program simply. According to the results of the experiment, the reflection coefficient was estimated high in short-period waves. However, 2-dimensional numerical experiment and 3-dimensional numerical experiment were the same in case of the long-period waves and high wave steepness. And to conclude in case of short-period waves the pressures were a relatively small difference between the two, but there was a big gap in longperiod waves and high wave steepness.