• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.54-60
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• 2006

This study discusses characteristic of spatiotemporal changes of the sand barrier in the Nakdong estuarine for the last century, focusing on geomarphologic evolution and mobility of sand barriers in the view of coastal engineering. The Nakdong estuarine, the research subject, has a complexly changing natural environment by interaction between ground and marine elements such as ocean wave, tidal current, sediment, etc. Moreover, recently, unnatural geomorphologic changes (e.g., seaside reclamation, new harbor construction, etc.) has been radically increased in this area with increasing desire for coastal development. Because of this, its sand barrier has developed quite unstable condition. Therefore, to identify the development process of geomorphologic changes in this area, required is a close examination on historical characteristics of spatiotemporal changes of the sand barrier in relation to surrounding seaside reclamation and physical environmental changes. This study, based on the marine charts published in between 1927 and 1995 year, analyzes the length and area of the sand barrier for the last hundred years, and investigates the cause of the changes by looking into the change of water depth for the last two years and doing ocean-physical site observations. In conclusion, the sand barrier of the Nakdong estuarine expands toward the open sea by $7.4{\sim}26m$ in annual average, maintaining a fixed distance of $1,241{\sim}1.279m$, and its area is expected to increase about $2.8km^2$ annually. This is characterized by the wocean wave from the open sea and the discharge of Nakdong River.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.87-94
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• 1999

Sand drain as a vertical drainage is widely used in soft ground improvement. Recently, sand, the principal source of sand drain, is running out. A laboratory model test was carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. D is the diameter of the column. The transient process of pore water pressure with loading and the characteristics of consolidation were studied with the data gained from the measuring instrument place on the surface of the container. The parameter study was performed for the marine clayey soil before and after the test in order to check the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. According to the test, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. As a result, it is assumed that gravel is relatively acceptable as a drainage material.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.83-89
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• 2004

The analysis about consolidation characteristic in soft clay has been depending one-dimension consolidation analysis. but, drain and undrain zone are explicated as homogeneous by consolidation behavior following consoli- dated settlementsoft in soft clay. 1) Established sand drain in soft clay in many types, and measured water content, unconfined compression strength, vertical stress, horizontal stress, vertical settlement, pore water pressure. 2) Arranged the result from the test and numerically explicated effective stress, total stress, and effective stress path at the drain and undrain zone. 3) We also analyzed and comparied elastic and elastic-plastic in soft clay using measured data. The result analyzed does not approach to a special theory, but, it is well in accord with the result of other investigator's study in the same condition.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.329-336
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• 1998

Sandmats are used to dissipate trapped water rapidly from the embankment built on marine soft ground. At present, however, it becomes difficult to obtain qualified sands since natural resources such as river sand are to exhausted. Also, low permeability of sand may cause low degree of consolidation and instability of embankment. In this study, design and construction methods was discussed. Drainage capacities of prefabricated horizontal drains which were installed in highway construction site are investigated in order to find possible substitution for river sands as drainage materials. On the basis of measurement data at the construction site, it was concluded that use of the prefabricated horizontal drains shows satisfactory drainage capacity without instability of embankment.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.96-106
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• 2004

A total of 116 surface sediment samples were obtained on the Yellow Sea and analyzed for grain size and geochemical elements in order to interpret the present sediment transportation. Thirty-nine cores and 3,070 line-km shallow seismic profiles are analyzed for sedimentary records of Yellow Sea in the past. Results show that the boundary of sediment transport between Korean side and Chinese side is about between $123^{\circ}E$ and $124^{\circ}E$. The similar result is produced from Shi et al. (in this publication). Two cyclonic patterns of surface sediments are recognized in the northeastern and southwestern Yellow Sea, while the strong front zone of the mud patch and sandy sediments are found in the southeastern Yellow Sea (the southwestern part of Korean coasts). The formation of fine-particle sediment packages, called for Northwest Mudbelt Deposit (NWMD), Hucksan Mudbelt Deposit (HSMD) and Jeju Mudbelt Deposit (JJMD), are resulted from eddies (gyres) of water circulations in the Yellow Sea. NWMD has been formed by cyclonic (anticlockwise) eddy. NWMD is composed of thick, homogeneous, relatively semi-consolidated gray clay-dominated deposit. On the other hand, HSMD and JJMD are formed by anticyclonic (clockwise) eddies. They are thick, homogeneous, organic-rich gray, silt-dominated deposit. Both core and surface sediments show that the middle zone across Chinese and Korean side contains bimodal frequency of grain-size distribution, indicating that two different transport mechanisms exist. These mud packages are surrounded by sand deposits from both Korea and China seas, indicating that Yellow Sea, which is the shallow sea and epicontinental shelf, is formed mostly by sand deposits including relict sands. The seismic profiles show such as small erosional/non-depositional channels, sand-ridges and sand-waves, Pleistocene-channelfilled deposits, a series of channels in the N-S major channel system, and thick Holocene sediment package, indicating that more complex sedimentary history exists in the Yellow Sea.

• Journal of Aquaculture
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• v.22 no.1
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• pp.118-121
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• 2009

This experiment was conducted to evaluate the effects of different substrates in rearing tank on growth and body composition of juvenile sea cucumber Apostichophus japonicus. Sea cucumber (average weight 3.6) were randomly distributed at a density of 10 juvenile per tank into nine tanks providing three different substrates including free-substrates, sand and wave-shaped plastic sheet as (shelter). Juveniles were fed with a commercial feed once in every 2 days for 8 weeks. At the end of the experiment, survival of sea cucumber was not affected by the presence of substrates (P>0.05). Weight gain and specific growth rate of sea cucumber reared in the tanks with sand were significantly higher than those of sea cucumber reared in the tanks with shelter and without substrate (P<0.05). Crude protein and crude lipid of whole body in sea cucumber reared in free-substrate tanks were significantly higher than those of juvenile reared in the tanks with other substrates (P<0.05). Higher ash content was obtained in sea cucumber reared in the tanks with sand compared to that of juvenile reared in the tanks with other substrates (P<0.05). The results of this study suggest that growth and proximate composition of whole body of sea cucumber was significantly affected by substrates. Among materials tested, sand may be a proper substrate for sea cucumber culture.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.143-156
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• 2014

We reviewed investigation status on turbidity plume in the statement of marine environmental survey(2008 to 2012) associated with marine sand extraction projects. The survey statement from seven marine sand extraction sites (extraction area of Southern EEZ, extraction area of Western EEZ, relocation zone in the Western EEZ, sea area under jurisdiction of Taean-gun, sea area under jurisdiction of Ansan City, and two discrete sea areas under jurisdiction of Ongjin-gun) in the nearshore and offshore of Korea showed that in situ observations were carried out for the dispersion and transport of suspended sediments on two areas (One is a extraction area in the EEZs, the other is an area of coastal sites). However, sampling station and range have not been selected considering physical, geographical factors (tide, wave, stratification, water depth, etc.) and weather conditions (wind direction and velocity, fetch, duration, etc). Especially turbidity plumes originating from three sources, which include suspended sediments in overflow(or overspill) discharged from spillways and reject chutes of dredging vessel, and resuspended sediments from draghead at the seabed, may be transported to a far greater distance outside the boundary of the extraction site and have undesirable impacts on the marine environment and ecosystem. We address that behaviour of environmental pollutants such as suspended solids, nutrients, and metals should be extensively monitored and diagnosed during the dispersion and transport of the plume. Finally we suggest the necessity to supplement the current system of the sea area utilization consultation and establish the combined guidelines on marine sand extraction to collect basic data, to monitor cumulative effects, and to minimize environmental damages incurred by the aftermath of sand extraction.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.106-106
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• 2017

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.32-41
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• 2000

Sand drain as a vertical drainage is widely used in soft ground improvement Recently, sand, the principal source of sand drain, is running out. The laboratory model tests were carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. The characteristics of consolidation were studied with data obtained from the measuring instrument place on the surface of the container. The parameter study was performed on the marine clayey soil before and after the test in order to verify the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. In-situ tests area was divided into two areas by material used. One is Sand Drain(SD) and Sand Compaction Pile(SCP) area, the other is Gravel Drain(GD) and Gravel Compaction Pile(GCP) area. Both areas were monitored to obtain the information on settlement, pore water pressure and bearing capacity by measuring instruments for stage loading caused by embankment. The results of measurements were analyzed. According to the test results, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. It is assumed that gravel is relatively acceptable as a drainage material. Gravel is considered to be a better material than sand for bearing capacity, and it is found that bearing capacity is larger when gravel is used as a gravel compaction pile than as a gravel drain.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.165-171
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• 2014

This study aims to examine whether Marine sand mining business is Maritime Traffic Safety Audit and priority between Maritime Traffic Safety Audit and Sea Area Utilization Impact Assessment because development and action to use in the ocean is ambiguous, it is overlapped with system of environmental aspect, and priority is not designated. Therefore, the way to improve to settle the overlapping problem etc. between Maritime traffic Safety Audit and Sea Area Utilization Impact Assessment was suggested and legal ground for sand mining is suggested. Because management department for Maritime Safety Act and Marine Environment Management Act is Ministry of Oceans and Fisheries, the solution for this is both embodying co-experts on each committee for determinant of system with maintaining contact and radical revise of law. If revised, the possibility of accident in ocean is decreased, and it can be a way to protect marine environment.