• The Journal of the Petrological Society of Korea
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• v.1 no.2
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• pp.104-123
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• 1992

We present petrography, mineral chemistry of amphibole and plagioclase, and major and trace element chemistry for the Ogcheon metabasites occurring in the Poun and Mungyong areas to understand metamorphism, and to define chemical characteristics of parental rocks and their implication for tectonic environment. The Ogcheon metabasites often preserve relict igneous textures, although no primary phases are observed. They are mainly composed of amphibole (actinolite+hornblende)+plagioclase+epidote+chlorite+sphene+opaque oxides, indicating epidote amphibolite facies metamorphism. Coarse-grained amphiboles frequently have actinolitic composition in the core, and hornblende along the margin and cleavage, which can be interpreted either as miscibility gap or as result of polymetamorphism. Although presumed polymetamorphic events in the Ogcheon supergroup favor the latter possibility, further metamorphic studies are necessary to solve the problem. Amphibole and plagioclase chemistries suggest greenschist (epidote-amphibolite, if miscibility gap is present) to amphibolite facies metamorphism of possibly medium pressure. The major and trace element data of whole rocks indicate that the Ogcheon metabasites are transitional to tholeiitic basalts belonging to within-plate environment. Absence of evidences indicating deep sea environment suggests that the Ogcheon metabasites emplaced in an intra-cratonic, possibly rift environment which failed to proceed to an oceanic rift. Chemical variation of the metabasites toward a granitic pluton indicates K loss closer to the pluton, suggesting that caution should be taken when K is involved in a discussion.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.599-615
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• 2022

In order to excavate underground tunnel most safely such as Han river, the slurry shield TBM method is applied to cope with face of high water pressure for many metro projects. In downtown subway project most of excavated soil is discharged externally whereas in road construction excavated soil is used as filling materials so it becomes important factor for success of the project. After excavated soil, weathered rock and soft rock are discharged with bentonite through discharge pipe to slurry treatment plant then those soils are separated in separation plant according to those size. Fine grained soil has been discarded together with filter cake but it is not toxic and can be mixed with coarse aggregate in proper ratio so this study is performed to find use of qualified filling material to meet quality standard. Therefore, in this study, legal standards and quality standards for the utilization of excavated soil of the slurry shield TBM method were examined and test was conducted to derive recycling way for filter cake and aggregate. And a plan for using it as a filling material for road construction was derived. Because bentonite is a clay composed of montmorillonite, and the excavated soil in the tunnel is also non-toxic, disposal of this material can waste social cost so it is expected to be helpful in the underground space development project that carries out the TBM project by recycling it as a valuable resource.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.595-603
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• 2021

Sand layer distribution, which is the main target of river and land aggregate resources, mainly belongs to alluvial and river sedimentary environments among the Quaternary sedimentary environments. The distribution of aggregate resources in the area of Geumsan-gun, Chungcheongnam-do is characteristically developed around a sedimentation environment in which intrusive meandering river dominate. Although the area around Bonhwangcheon Stream and the area near the confluence of small streams are small, the river floodplain develops and corresponds to the aggregate distribution area. The sedimentary layer formed in the sedimentary environment such as colluvial deposits or alluvial fan deposits has a relatively low distribution rate of aggregate resources. The vertical distribution of the Quaternary sedimentary layers in the Geumsan-gun region ranges from about 5 to 12 m and has an average Quaternary sedimentary thickness of 8 m. The aggregate-bearing section has an average thickness of 3.6 m, and the average grain size is about 21% clay-silt, 67% sand, and 12% gravel. The main characteristics of the aggregate-bearing section are that coarse-grained sand predominates, and gravel is sub-angular or sub-rounded, and the sorting is generally poor and has a massive form of deposits, and the soil colour ranges from dark grey to yellowish-brown. In Geumsan-gun, the most likely distribution area for aggregate development is the alluvial sedimentary and river sedimentary layers distributed along the current and former riverbeds of the main Geumgang River, Bonhwangcheon and small River tributaries.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.4
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• pp.179-191
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• 2018

In order to determine the distribution characteristics of the heavy metals in surface sediments of the eastern Yellow Sea, heavy metal concentrations (Cu, Pb, Zn, Cd, Cr, Mn, As, Ni, Co, Li, Fe and Al) together with grain size and total organic carbon (TOC), were analyzed. The concentrations of all heavy metals, with the exception of Pb, Mn and As in some stations, were relatively high in the central area of the Yellow Sea and tended to decrease toward the Korean coast. A significant relationship between grain size and concentrations of heavy metals suggested that they were mostly controlled by quartz dilution effect. However, at some stations, Pb, Mn and As exhibited different distribution patterns. For Pb, the differences were caused by petrogenetic influences (feldspar) in coarse-grained sediments. In the case of Mn, biogenetic influences ($CaCO_3$) affected distribution patterns. As was distributed differently because of the existence of a heavy mineral (pyrite). A comparison with previous data (collected in 2000) shows that the heavy metal concentration in the eastern Yellow Sea has not increased over the past fifteen years. The sedimentary environment of dumping sites in the Yellow Sea has not been significantly improved during this period. The results of the pollution assessment revealed that the concentrations of heavy metals in the study area were lower than lower criteria (TEL, MSQ-1) in Korean and Chinese sediment quality guidelines. The enrichment factor (EF), geo-accumulation index ($I_{geo}$) and ecological risk index (ERI) of Cu, Pb, Zn and Cr were higher in the central area of the Yellow Sea.

• Economic and Environmental Geology
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• v.52 no.3
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• pp.213-221
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• 2019

The Wugang banded iron formation (BIF) is located within the Taihua complex at the southern margin of the North China Craton (NCC). In this study, we analyzed major elements and rare-earth elements in iron ores from the Wugang BIF, to study the type of BIFs and their formation mechanism in combination with previously-published data from the literature. We found that the iron ores from the Wugang BIF display two types of banding textures, which can be described as weak banding or no banding. The samples are composed of coarse-grained magnetite, quartz, pyroxene, and amphibole. Based on our geochemical results, mixing of a hydrothermal fluid with sea water led to the precipitation of the Wugang BIF, and there is evidence of crustal contamination. These results, combined with previous literature data, almost all of the iron ores lack Ce anomalies, though some samples show negative Ce anomalies. Our results indicate that the Wugang BIF was formed in a dominantly reducing environment, although the surfaces were relatively oxidized. Geochemical evidence suggests that the Wugang BIF iron ores were formed in a near-shore continental-shelf environment or in a back-arc basin. The BIF is known as interbedded with migmatite, amphibole gneiss, minor quartz and marble, which indicating lack of volcanic materials input. This study, combined with previous results on geochemical interpretation of related wall rock of Wugang BIF, demonstrated that Wugang BIF belongs to Superior-type BIF.

• Journal of the Korean earth science society
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• v.42 no.2
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• pp.164-174
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• 2021

The study examines the shearing and crushing characteristics of land-derived subaqueous granular materials in a gravel-bed river. A series of large-sized ring shear tests were performed to examine the effect of shear time and shear velocity on the shear stress characteristics of aquarium gravels with a 6-mm mean grain size. Three different shear velocities (i.e., 0.01, 0.1, and 1 mm/sec) were applied to measure the shear stress under the drained (long-term shearing) and undrained (short-term shearing) conditions. Different initial shear velocities, i.e., 0.01→0.1→1 mm/sec and 0.1→0.01→1 mm/sec, were considered in this study. The test results show that the grain crushing effect is significant regardless of drainage conditions. The shear stress of coarse-grained materials is influenced by initial shear velocities, regardless of the drainage conditions. In particular, particle breakage increases as grain size increases. The shearing time and initial shear velocity are the primary influencing factors determining the shear stress of gravels. The granular materials may be broken easily into particles through frictional resistance, such as abrasion, interlocking and fracture due to the particle-particle interaction, resulting in the high mobility of granular materials in a subaqueous environment.

• Korean Journal of Ecology and Environment
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• v.55 no.2
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• pp.145-155
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• 2022

Koreoleptoxis nodifila (Martens, 1886) is an endangered species only living in the central and north streams of South Korea. However, there is a lack of information on physical habitat characteristics of K. nodifila. We aimed to determine preference ranges for water depth, current velocity, streambed substrate of K. nodifila. The weibull model was used to estimate the habitat suitability based on distribution of individual abundance by physical factors. Optimal depth preferences ranged from 0.53~17.17 cm, current preferences ranged from 48.40~81.03 cm s^-1 and substrate (𝜱_m) preferences ranged from -4.36~ -2.26. Median values of central tendency were determined as follows: water depth 16.73 cm, current velocity 65.23 cm s^-1, substrate -3.51. Mean values of central tendency were determined as follows: water depth 21.32 cm, current velocity 65.65 cm s^-1, substrate -3.63. Mode values of central tendency were determined as follows: water depth 5.17 cm, current velocity 64.77 cm s^-1, substrate -3.24. Based on the habitat suitability analysis, the microhabitat types of K. nodifila were determined as riffle and coarse-grained streambed.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.5-18
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• 2023

The construction timeline for earthworks can be significantly reduced by substituting the conventional layer-by-layer compaction using a vibratory roller with single-layer compaction through the rapid impact compaction (RIC) method. Dynamic load compaction is well-suited for coarse-grained soils like sand. However, as the supply of sand, the primary reclamation material, becomes scarcer, the utilization of soil with fines is on the rise. To implement the dynamic load compaction, such as RIC, with reclaimed materials containing fines, it's imperative to determine the effective improvement depth. In this study, we assess the impact of the RIC method on the effective improvement depth for clean sand and public fill with fines, comparing field test results before and after RIC application. Our focus is on the cone resistance (q_c) as it pertains to compaction quality control criteria. In conclusion, it becomes evident that standardizing the cone resistance is vital for the quality control of various reclaimed soils with fines. We have evaluated the compaction quality control criteria corresponding to a relative density (Dr) of 70% for clean sand as Q_tn,cs = 110. As a result of this analysis, we propose new quality control criteria for q_c, taking into account the fines content of reclaimed soils, which can be applied to RIC quality control.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.837-844
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• 2023

Small and medium-sized mountain rivers that flow through steep, confined valleys carry large amounts of coarse-grained sediment and woody debris during floods. It causes an increase in flood water level by aggrading the riverbed and the cross-section blockage due to driftwood accumulation during flooding. However, the existing flood level calculation in the river basic plan does not consider these changes. In this study, using the Typhoon Hinnamnor flood in September 2022 as an example, we performed numerical simulations using the HEC-RAS model, taking into account the blockage of a cross-section at the bridge and changes in riverbed elevation that occurred during floods, and analyzed the flood level to predict flood risk. This study's results show that flooding occurs if more than 30% of the cross-section is blocked. The rise of flood water levels corresponds to that of the riverbed due to sediment deposition. These results can be used as basic data to prevent and effectively manage flood damage and contribute to establishing flood defense measures that consider actual phenomena.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.81-92
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• 2001

According to analyses of high-resolution seismic profiles (air gun, sparker, and SBP) and a deep-drill core(YSDP 105) in the mid-eastern Yellow Sea, stratigraphic and geoacoustic models have been established and seismo-acoustic modeling has been fulfilled using ray tracing of finite element method. Stratigraphic model reflects seismo-, litho-, and chrono-stratigraphic sequences formed under a significant influence of Quaternary glacio-eustatic sea-level fluctuations. Each sequence consists of terrestrial to very-shallow-marine coarse-grained lowstand systems tract and tidal fine-grained transgressive to highstand systems tract. Based on mean grain-size data (121 samples) of the drill core, bulk density and P-wave velocity of depositional units have been inferred and extrapolated down to a depth of the recovery using the Hamilton's regression equations. As goo-acoustic parameters, the 121 pairs of bulk density and P-wave velocity have been averaged on each unit of the stratigraphic model. As a result of computer ray-tracing simulation of the subsurface strata, we have found that there are complex ray paths and many acoustic-shadow zones owing to the presence of irregular layer boundaries and low-velocity layers.