• Ocean and Polar Research
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• v.29 no.4
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• pp.411-418
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• 2007

We studied the bottom morphology and sedimentary environments of the Masan Bay using high-resolution Chirp seismic profiles and sediments data. According to deep-drilled core samples (up to 20 m thick) penetrated into the weathered rock basement, the sediments consist largely of three sediment types: the lower sandy gravel facies (Unit I) of 1-4 m in thickness, the middle sandy mud and/or muddy sand facies(Unit II) of 1-2 m thick and the upper mudfacies (Unit III) of over 10 m in thickness. The sedimentary column above the acoustic basement can be divided into two major sequences by a relatively strong mid-reflector, which show the lower sedimentary sequenc e(T) with parallel to subparallel internal reflectors and the upper sedimentary sequence(H) with free acoustic patterns. Acoustic basement, the lower sedimentary sequence (T), and the upper sequence (H) are well correlated with poorly sorted massive sandy gravels (Unit I), the sand/mud-mixed sediment (Unit II), and the muddy facies(Unit III), respectively. The acoustic facies and sediment data suggest that the Masan bay is one of the most typical semi-enclosed coastal embayments developed during the Holocene sea-level changes. The area of the Masan Bay reduced from about $19\;km^2$ in 1964 to about $13\;km^2$ in 2005 by reclamation, and its bottom morphology changed as a result of dredging of about $2{\times}10^7\;m^3$.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.100-109
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• 2004

Is this study, results of static pile load tests of in-situ cast piles in weak or uncemented sedimentary rock layers have been analyzed and presented. Consdierations on the characteristics of soils sedimentary rocks have been made. From the measurements of strain gauges and extensometers the relationship of unit skim friction versus displacement and that of unit end bearing versus displacement have been obatined to verity the characteristics of bearing capacity of this uncemented sedimentary rock layers. Also, a comparison has been made between ultimate skin friction in compression and tension.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.6
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• pp.683-694
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• 2009

High-resolution (Chirp and Sparker system) seismic profiles were analyzed to investigate the sedimentary sequence and distribution pattern of the late Holocene deposits in Gyunggi Bay, the Yellow Sea. The bay is located in the western part of Korea, east of the Yellow Sea. The sedimentary sequence divided into three units bounded by erosional bounding surface: (1) acoustically parallel to subparallel reflectors with cross bedding structures (Unit 1); (2) confused inner reflectors and top of unit exposed partially at the seafloor (Unit 2); and (3) approximately parallel reflections and regressive to transgressive incision-fills (Unit 3). On the basis of seafloor morphology, surface bedforms, and subbotom acoustic characters, echo types in the study area were identified following the schemes of Chough et al. (2002); (1) flat seafloor with sharp bottom echoes (echo types 1-1, 1-2 and 1-3; transgressive sediment sheets or relict sands), (2) mounded seafloor with either smooth surface or superposed bedforms (echo types 2-1 and 2-2; tidal ridges), and (3) various-scale eroded seafloor (echo types 3-1 and 3-2; channels). Suspect features of acoustic turbid zones which is related to gas charged sediment are reported.

• Journal of the Korean earth science society
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• v.33 no.1
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• pp.1-10
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• 2012

Analysis on high-resolution seismic and core data reveals that the sedimentary strata in Gyeonggi Bay consists of four sedimentary units (Unit I-IV, from top to bottom) formed during the late Quaternary period. Unit I is interpreted as sediments of tidal flat and channel-fill deposits, formed during the Holocene transgression. Unit II is divided into shallow-marine facies unit in offshore area and channelized fluvial to estuarine facies unit in nearshore sand ridge and tidal flat. Unit III is considered as tidal flat deposits with the uppermost severely weathered and oxydized layers. This unit is composed of shallow marine sedimentary successions formed during the MIS-5 highstand. The lowermost Unit IV rests on Mesozoic basement rocks, considered as the shallow marine and shelf deposits formed before the MIS-5 lowstand.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.882-887
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• 2006

Sedimentological, geochemical, geophysical and micropaleontological analyses of 10 borehole cores were carried out to understand depositional environment and sequence stratigraphy of late Quaternary sedimentation in the estuary of the Nakdong River. Holocene Formation in study area is classified into five sedimentary units. Early Holocene freshwater lower pebbly sandy deposit(Unit I), lower muddy deposit(Unit II), middle thin sandy deposit(Unit III), upper muddy deposit(Unit VI), and upper sandy deposit(Unit V), in ascending order contolled by global sea-level change since interglacial period(about 15,000 yrs B.P.). Unit I deposited in erosional environments before marine trangression. Unit II and Unit VI composed of clay were deposited in cold and worm currents for marine trangression., respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.138-150
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• 1997

The late Quaternary stratigraphy of the tidal deposits in the Hampyung Bay, southwestern coast of Korea comprises 1) Unit III (nonmarine fluvial coarse-grained sediments), 2) Unit II (late Pleistocene tidal deposits), and 3) Unit I (late Holocene fine-grained tidal deposits) in ascending order. The basements of the Hampyung Bay is composed of granitic rocks and basic dyke rocks. These three units are of unconformally bounded sedimentary sequences. The sequence boundary between Unit I and Unit II, in particular, seems to be significant suggesting erosional surface and exposed to the air under the cold climate during the LGM. The uppermost stratigraphic sequence (Unit I) is a common tidal deposit formed under the transgression to highstand sea-level during the middle to late Holocene.

• Journal of the Korean earth science society
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• v.24 no.8
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• pp.657-667
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• 2003

Deep-drilled core sampling and high-resolution seismic survey were carried out to identify a Holocene-late Pleistocene boundary in Gyeonggi Bay, western coast of Korea. Analysis of core sections revealed the existence of an oxidized and semi-consolidated sediment layer, Iying immediately below a Holocene horizon (Unit I) and being developed at the top of a late Pleistocene deposit (Unit II). The oxidized sedimentary layer (uppermost part of Unit II) is characterized by semi-consolidated, yellowish sediments showing signs of desiccation and alteration such as high N value, low water content, periglacial cryogenic structure, depletion of smectite, and high geochemical weathering index (Ba/Sr ratio). This feature, together with radiocarbon ages, suggests that the layer has formed as a result of prolonged subaerial exposure of Unit II sediments during the late Wisconsin sea-level lowstand, producing a regional unconformity. Such unconformitic-bounding surface corresponds to a prominent near-surface reflector (R), which is observed in seismic profiles obtained across the drilled-core sections in the study area. Consequently, the buried oxidized-sedimentary layer associated with the seismic reflector possibly plays a key horizon for the understanding of late Quaternary environmental changes as well as evidence of the emergence of the Yellow Sea shelf during the late Wisconsin sea-level lowstand.

• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.51-59
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• 2009

This study is based on field data obtained from rock grouting such as RQD value, Unit cement grout volume, Lugeon value(Lu), and Maximum grout pressure in four different dam sites. The relationship were analyzed and compared as follow. The cut-off effect after rock grouting in dam-foundation which are mostly consist of metamorphic rock is better than that of Sedimentary rock. And the impermeable effect after consolidation grouting is more efficiency than the impermeable effect after curtain grouting. The unit cement grout volume are increased as RQD value is higher in rock mass. But there is no relationship between RQD value and Lugeon value. In the sedimentary rock, which is more permeable than metamorphic rock, Lugeon value (Lu) is a linear function (Lu=0.22Vc) of unit cement grout volume (Vc). Cut-off effect of curtain grouting is less influential at each near holes which are already grouted than that of consolidation grouting. And the behavior characteristics of Lugeon value vs. the unit cement grout volume as the order of installations are almost the same.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.13-14
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• 2003

It is generally well known that Quaternary is characteristic geologically in terms of glacial and interglacial repeats and their associated unconformity formation. This paper deals with the first finding of the characteristic and significant meaningful unconformity between Holocene and late Pleistocene, which implies submergence and emergence of the tidal sedimentary basin along the western coastal zone of Korea during interglacial stage(IOS-5e) and glacial time(IOS-2). The stratigraphy of intertidal deposits in the Haenam Bay, western coast of Korea shows two depositional sequence units (Unit I of Holocene and Unit II of late Pleistocene) bounded by an erosional surface of disconformity. The disconformity is related to the latest Pleistocene sea-level lowstands (probably during the LGM). The Unit II is interpreted as intertidal deposit showing tidal sedimentary structures and crab burrow ichnology and has two parts (the upper part and the lower part) showing different lithology and character. The upper part of Unit II shows characteristic subaerial exposure features (emergence) and its related lithology. Such subaerially exposed upper part (more or less 4m to 5m in thickness) is characterized by yellow-brownish sediment color, cryoturbat-ed structure, crab burrow ichnofacies and high value of shear strength. Geochemical and clay mineral analyses of the upper part sediments also indicate subaerial exposure and weathering. In particular, very high value of magnetic susceptibility of the upper part in comparison to that of the lower part is interpreted as pedogenetic weathering during the subaerial exposure period.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.55-68
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• 2012

The west seacoast has approximately 83% of tidal flat in Korea. Gyeonggi-do and Inchon has 35.1%. This study was carried out to understand depositional environment and properties of tidal deposits that distributed in the Gyeonggi bay. On the basis of observation and description on mineralogical, geochemical, physical properties, detailed sedimentary unit has been respectively distinguished Based on. stratigraphic position, facies and unconformity, the intertidal zones are classified into four sedimentary units, and bedrock over the units has been developed in the order of Unit 4${\rightarrow}$Unit 3${\rightarrow}$Unit 2${\rightarrow}$Unit 1. The intertidal sediment deposits of Gyeonggi Bay were compared with those of west coast. In Cheongra area all strata of Unit 4-Unit 3-Unit 2-Unit 1 appear. In Yeongjong-do Unit 2-Unit 1, in Incheon Bridge and Songdo area Unit 4-Unit 3-Unit 1 are observed. In Daesan area Unit 4-Unit 3-Unit 1 are observed. Average clay mineral content ratio is 8.2% in Cheongra area, 2.9% in Yeongjong Island, 18.4% in Incheon Bridge, 24.6% in Songdo area.