• Journal of the Korean earth science society
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• v.34 no.2
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• pp.120-135
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• 2013

To investigate the changes in depositional environment around Gangneung Harbor, we analyzed the surface sediment textural parameters and topography data collected five times from February 2007 to February 2009. In the study area, sediments were mainly composed of sand and its sediment size became finer at offshore sites. During summer time, however, the sand grains became coarser than winter season near Namhangjin Beach, inside the harbor, and offshore areas. On the other hand, the grain size of Anmok Beach showed a gradual finer trend with time. Compared with the previous studies conducted before the completion of Gangneung Harbor construction, the mean grain size became finer on Anmok Beach, while it was coarser on Namhangjin Beach. The bathymetric changes observed over a 2-year period showed predominant erosion in the area of 5 to 10 m water depths and deposition in 2 to 5 m water depths. The shallower area less than 2 m water depths showed an alternating trend and yet slightly more dominant erosion process. The sediment textural parameters and the distribution of erosion and deposition have changed continuously. Results imply that such changes show long-term trends as well as seasonal variations in which the trend may have been formed after the completion of Gangneung Harbor construction.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.574-578
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• 2006

Tidal amplification by construction of the sea-dike and sea-walls had been detected not only near Mokpo Harbor but also at Chungkye Bay which is connected with Mokpo Harbor by a narrow channel. This brings about increase of tidal flat area and in particular increase of surge-wave combined runup during storms. The purpose of this study is to examine an efficient operational model that can be used by civil defense agencies for real-time prediction and fast warnings on wind waves and storm surges. Instead of using commercialized wave models such as WAM, SWAN, the wind waves are simulated by using a new concept of wavelength modulation to enhance broader application of the hyperbolic wave model of the mild-slope equation type. Furthermore, The predicting system is composed of easy and economical tools for inputting depth data of complex bathymetry and enormous tidal flats such as Mokpo coastal zone. The method is applied to Chungkye Bay, and possible inundation features at Mokpo Harbor are analyzed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.6 no.1
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• pp.11-22
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• 2000

The paper describes creation methods of background scenes to implement realistic virtual environments in the VRSS (Virtual Reality Ship Simulator). VRSS is next-generation system constructed with virtual tools in a virtual space. Thus, it could have many benefits compared to conventional ship simulators composed with heavy bridge mock-up system and wide visual presentations. In this work, we developed effective 3D object modeling techniques, and constructed virtual harbor scene by using 3D-Webmaster authoring tool. The virtual harbor was built with object-oriented 3D objects modeled to interact with user's action. With the immersion-type VR system, we created virtual harbor environments in a virtual space, and discussed on the naturalness of the scene with test results of SDMPA (Semantic Differential Method for Psychophysical Assessment) by 10 subjects. As the results of subject assessment, all of the participants could felt natural-like harbor. Therefore, we found that the proposed creation methods and procedures of background scene are enabling to fit to the full mission VRSS construction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.53-58
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• 2006

Today, harbor oscillation problems are the most significant factor to consider when designing harbors serving very large ships. In coastal harbors, large vessels moored in the elastic hawsers are often displaced due to the resonance between long period waves and mooring systems. As a result, cargo handling may be interrupted and the hawsers may be broken, especially when the amplification becomes extreme. The most significant harbor confronted with harbor oscillation problem in Korea is Pohang New port. Many cases of problems are being reported by the pilot association and the local office of MOMAF (Ministry of Maritime Affairs and Fisheries). However, it is difficult to prevent the arrival of long waves causing oscillation within this harbor. Moreover, the Korean government has already started a new port plan at the mouth of Yeongil Bay without addressing the problems that have occurred in Pohang New port. This study deals with the variation of harbor oscillation due to the construction of a 4.1 km breakwater at the bay mouth including the arrangement of the new berths. Numerical methods used are in fairly standard form from the extended mile slope equation. The obtained numerical results were compared with field measurement from the previous and this will bring a certain level of discussion and consideration of variation to the future port development.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.299-308
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• 2011

In this study, we develop a pressure observer to measure the cylinder length of a harbor-construction robot. For the robot control, sensors are required to measure the length of a hydraulic cylinder. The cylinder-position sensor is relatively expensive when the operating environment prohibits external approaches for the measurement of the cylinder position. LVDT or linear scales are usually mounted on the outside of the cylinder, which causes poor durability on a construction site. We use a pressure sensor to indirectly estimate the length of the cylinder. The pressure sensor is mounted inside a hydraulic valve box so that it is protected by the box and easy to waterproof for an underwater robot. By treating oil as a compressible fluid, we derive the nonlinear pressure dynamics as a function of the cylinder position, velocity, and pressure. The recursive least squares (RLS) algorithm is applied to identify the dynamic parameters, and the pressure observer estimates the cylinder position through the pressure acting on the head and the rod of the hydraulic cylinder. The position accuracy is relatively low, but it is acceptable for a construction robot that handles large armor stones.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.2
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• pp.38-45
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• 2003

This paper intends to analyze the movement characteristics of the suspended solid(SS) generated in a riprap work which is the most widespread process in harbor construction. The generation and movement behaviors of SS are investigated when 1) basic ripraps (0.001~0.03㎥) are cast for breakwater construction, 2) ripraps are loaded on carrier for riprap casting in the sea-wall construction of dredged material pocket, and 3) ripraps for inner filling are cast. The result of the present study shows that the SS generation is considerable when basic ripraps are cast for breakwater construction and the SS diffusion reaches up to 500m in high tide period. When ripraps are loaded on carrier, the SS is generated by the ripraps running down into sea from carrier, thereby showing a high concentration of SS in the vicinity of carrier. In the surface layer, SS distribution is confined in the vicinity of the carrier due to the prompt sinking of the SS. However the SS in the bottom layer is diffused approximately up to loom and then the SS concentration reaches to the background one. In the riprap (less than 0.03㎥) casting for inner filling using pork crane, SS is diffused approximately up to 300m in the surface layer and more than 300m in the bottom layer. It is quite interesting that the movement of the SS generated in harbor construction is mainly controlled by wind drift in the surface layer and tidal current in the bottom layer, and also the diffusion range of SS in the bottom layer is much larger than that in the surface layer.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.2
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• pp.97-104
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• 1997

A hyperbolic numerical model with multi-directional waves has been used to investigate harbor tranquility in Pohang New Harbor. Comparing numerical results with field data measured at two stations in the harbor, it was found that use of input condition of multi-directional waves is superior to the use of uni-directional waves. Calculations with unidirectional wave input give errors of about 12% at St. P2 and 26% at St. P3, while calculations with multi-directional wave input give errors of 4 % at St. P2 and. 14% at St. P3. Using the input condition of multi-directional waves, we investigate the tranquility of Pohang New Harbor with two layouts : the condition in 1994 when the downtime at the 7th pier was often reported and the condition in 1996 when the 4th disposal site was constructed. The numerical results show that the problem of downtime at the 7th pier cannot be solved by the construction of the 4th disposal site.

• 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.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.230-241
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• 2020

Since the construction of Pohang New Port, the problems of the low harbor tranquility caused by decreasing port operation rate has been continuously reported. In order to improve the harbor tranquility, a detached breakwater (DB) has been constructed outside the outer breakwater of Pohang New Port in 2018~2020. In this study, the effectiveness of the DB was proved by comparing the reduction rates of wave heights that were observed before and after the construction of the DB. First, the observed data were compared with the numerical model results available from a previous study, and the model data showed reasonable agreement with measured data at 3 out of 4 locations inside the port. The discrepancy in one of the locations was because the model could not accurately calculated the effect of wave interference in the inner corner of the port. The observation data showed excellent results that the number of waves that exceeded 0.3 m, the critical value to reach desired harbor tranquility, was significantly reduced after the construction of the DB. In addition, the reduction rate, the ratio of wave heights between outside and inside of the port, was decreased after the DB construction, which proved that properly designed coastal structures such as DB in this study could be effective in improving the port tranquility. The results of this study can be usefully applied for solving problems in similar cases.

• Journal of Environmental Health Sciences
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• v.35 no.4
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• pp.304-314
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• 2009

A new harbor as been constructing in Gadukdo. However, a lot of fugitive dust gas been often generated from construction site reclaiming sea sand, especially when the Northwester is blown strongly. It has resulted insome appeals of residents in Gadukdo. In this study, we estimated the amount of fugitive dust caused by new harbor construction using Fugitive dust formula. Also, the concentration of PM10 for recipient is predicted by AERMOD. The amount of fugitive dust is 26.56 ${\mu}g/sec{\cdot}m^2$ and 11.84 ${\mu}g/sec{\cdot}m^2$ respectively by the Fugitive dust formula. PM10 outlet concentration and the amount of fugitive dust increase according to wind velocity and directions. AERMOD is performed on the basis of weather data and the amount of fugitive dust generated with wind velocity. As a result of AERMOD, the PM10 concentration of Sunchang and Oinul are predicted over 100 ${\mu}g/m^3$. The PM10 concentration of Sunchang and Oinul are predicted over 130 ${\mu}g/m^3$ when wind velocity of northwester in winter is over 11 m/s (Air Quality for Particulate Matter (100 ${\mu}g/m^3$ for 24 hours)). Also, the measured error between AERMOD and actual measurement is lower than 5%.