• Korean Journal of Remote Sensing
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• v.40 no.1
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• pp.19-31
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• 2024

Ports are vital social infrastructures that significantly influence both people's lives and a country's economy. In South Korea, the aging of port infrastructure combined with the increased frequency of various natural disasters underscores the necessity of displacement monitoring for safety management of the port. In this study, the time-series displacements of Yeongilman Port and surrounding areas in Pohang, South Korea, were measured by applying Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) to Sentinel-1 SAR images collected from the satellite's ascending (February 2017-July 2023) and descending (February 2017-December 2021) nodes, and the displacement associated with the 2017 Pohang earthquake in the port was analyzed. The southern (except the southernmost) and central parts of Yeongilman Port showed large displacements attributed to construction activities for about 10 months at the beginning of the observation period, and the coseismic displacement caused by the Pohang earthquake was up to 1.6 cm of the westward horizontal motion and 0.5 cm of subsidence. However, little coseismic displacement was observed in the southernmost part of the port, where reclamation was completed last, and in the northern part of the oldest port. This represents that the weaker the consolidation of the reclaimed soil in the port, the more vulnerable it is to earthquakes, and that if the soil is very weakly consolidated due to ongoing reclamation, it would not be significantly affected by earthquakes. Summer subsidence and winter uplift of about 1 cm have been repeatedly observed every year in the entire area of Yeongilman Port, which is attributed to volume changes in the reclaimed soil due to temperature changes. The ground of the 1st and 2nd General Industrial Complexes adjacent to Yeongilman Port subsided during the observation period, and the rate of subsidence was faster in the 1st Industrial Complex. The 1st Industrial Complex was observed to have a westward horizontal displacement of 3 mm and a subsidence of 6 mm as the coseismic displacement of the Pohang earthquake, while the 2nd Industrial Complex was analyzed to have been little affected by the earthquake. The results of this study allowed us to identify the time-series displacement characteristics of Yeongilman Port and understand the impact of earthquakes on the stability of a port built by coastal reclamation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.679-687
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• 2019

This paper presents the autonomous swimming technology developed for an Autonomous Underwater Vehicle (AUV) operating in the underwater jacket structure environment. To prevent the position divergence of the inertial navigation system constructed for the primary navigation solution for the vehicle, we've developed kinds of marker-recognition based underwater localization methods using both of optical and acoustic cameras. However, these two methods all require the artificial markers to be located near to the cameras mounted on the vehicle. Therefore, in the case of the vehicle far away from the structure where the markers are usually mounted on, we may need alternative position-aiding solution to guarantee the navigation accuracy. For this purpose, we develop a sonar image processing based underwater localization method using a Forward Looking Sonar (FLS) mounted in front of the vehicle. The primary purpose of this FLS is to detect the obstacles in front of the vehicle. According to the detected obstacle(s), we apply an Occupancy Grid Map (OGM) based path planning algorithm to derive an obstacle collision-free reference path. Experimental studies are carried out in the water tank and also in the Pohang Yeongilman port sea environment to demonstrate the effectiveness of the proposed autonomous swimming technology.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.300-311
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• 2019

An ROV trencher is a type of heavy-duty work class ROV equipped with high-pressure water jet tools for cutting into the sea floor and burying cables. This kind of trencher is mostly used for PLIB operations. This paper introduces the development of this kind of ROV trencher, which has a 698 kW power system, with a 250 kW hydraulic system and two 224 kW water jet systems. The project was launched in January 2014. After four years of design, manufacturing, and system integration, we carried out two sea trials near the Yeongilman port (about 20-30 m in depth) in Pohang to evaluate the system performance in November 2017 and August 2018. Through tests, we found that most of specifications were satisfied, including a maximum bury depth of 3 m, maximum bury speed of 2 km/h, and maximum forward speed of 1.54 m/s.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.386-394
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• 2019

In this study, according to drainage condition (undrained and drained) in ground, the settlement and horizontal displacement of caisson quay wall and apron in Yeongilman port due to excess pore water pressure in ground induced by the magnitude 5.4 earthquake in Pohang on November 15, 2017. In general, seismic response analysis was carried out under undrained drainage condition, but in this study, drain drainage analysis was conducted to estimate displacement during earthquake as well as an additional displacement due to dissipation of excess pore water pressure after earthquake. The result of after earthquake can not be known under undrained drainage condition. Results cleary showed that the behavior of structure and ground was dependent on drainage condition in ground. Especially, based on the drained drainage condition, the additional displacement was clearly detected due to dissipation of excess pore water pressure after earthquake. Which indicates that both results are different to drainage condition in ground, and therefore, drainage condition analysis is necessary to accurately estimate the behavior of ground and structure in seismic response analysis.