• Water for future
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• v.16 no.3
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• pp.171-179
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• 1983

In the Jeon Cheon Basin, unconsolidated alluvium and marine clay beds overlying Tertiary conglomerate and impermeable mudstone, and Cambro-Ordovician sedimentary rocks composed of mainly cavernous limestones, and age-unknowned crystalline rocks are occured. Most productive rock is Cambro-Ordovician limestones containing a lot of solution openings and secondary porosities and shows its transmissivity of 1836$m^2$/day and storativity of 1.47 $\times$ $10^{-3}$. The storage of deep seated groundwater in linestone aquifer is estimated about 1059 $\times$ $10^6$ metric tons, being equivalent to 6 years total precipitation of the basin. The safe yield of the groundwater to be abstracted from the aquifer is about 126,000 tons/day. To pump at least 100,000 tons/day of groundwater from the said aquifer, a well field comprising 34 deep wells ranging in depth from 80 to 100 meter and penetrating the cavernous limestone aquifer shall be established at middle and down stream area.

• Journal of the Mineralogical Society of Korea
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• v.32 no.4
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• pp.313-321
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• 2019

Diatomite is a silicic porous sedimentary rock composed of diatom frustules, used for filtration aid, filler, absorbent, abrasive, carrier, insulator, and fertilizer. During the calcination of diatomite to improve physical properties for filtration-aid application, amorphous silica is transformed to cristobalite. X-ray diffraction and scanning electron microscopy studies were carried out for 17 diatomite samples, showing that 16 diatomite samples contain cristobalite in the range of 6~100 %. Concentration of respirable cristobalite in air is regulated as harmful substances, but the residual cristobalite in food is treated as generally safe substance. The determination procedure of cristobalite content in food was established for managing food safety. Calibration curve of cristobalite filtered on silver membrane were obtained by X-ray diffraction. The lower limit of quantification was evaluated as 2.7 mg. The cristobalite was not detected in the analyses of selected food samples using the established procedure.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.119-122
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• 1998

Chemical analysis, measurement of pumping rates of 60 production wells and depth to water tables of 57 monitoring wells were carried to protect depletion of water resources and deterioration of water quality for the commercial portable ground-water. Borehole depth of production well averages 149m(31 boreholes), casing depth is 28m(29 boreholes), production rate is 70 $m^3$/day and depth to water table of monitoring well is 23.26m, respectively. The geology of 60 wells can be divided into Daebo granite(20), Okchun metarmorphic complex(18), Precambrian granitic gneiss(15), Bulguksa granite(4), Cheju volcanics(2), Cretaceous sedimentary rock(1). Average electrical conductivity and pH are 152$\mu$S/cm, and 7.35, respectively. The contents of major cation and anion predominantly $Ca^{2+}$>N $a^{+}$>M $g^{2+}$> $K^{+}$ and HC $O_{3}$$^{－}$ >S $O_{4}$$^{2-}$>Cl￣>F￣. Water type is predominantly $Ca^{2+}$-HC $O_{3}$$^{－}$(81.7%). It's possible that water chemistry of some wells were affected not only by the geology of boreholes penetrated but by inflows of surface water or shallow ground-water. Therefore, it is strongly necessary to steadily monitor the water quality and hydrogeologic conditins of production wells.ells.ls.ells.

• The Journal of the Petrological Society of Korea
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• v.22 no.4
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• pp.263-272
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• 2013

We investigated the lithology and petrography of granites and metasedimentary rocks in Deokjeok Island at the western margin of the Gyeonggi massif. The major lithology comprises the biotite granite that intrudes all other types of rocks. A minor amount of mylonitized porphyritic granite crops out along the southeastern coast. Metasedimentary rocks in the north are further divided into: (1) sheared quartzite-schist to the northeast; and (2) relatively less-deformed, low-grade metasedimentary rocks to the northwest. The former contains quartz grains showing undulatory extinction and subgrain aggregates as well as minor amount of primary chlorite and biotite in the muscovite-rich matrix. Metamorphic condition belongs to the greenschist facies or the biotite zone. On the other hand, the latter unit consists of meta-conglomerate, meta-sandstone, meta-pelite, and black slate. Regardless of the lithology, the intensity of deformation apparently increases eastward to develop the flow banding of quartz in the shear zone.

• Economic and Environmental Geology
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• v.29 no.5
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• pp.561-573
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• 1996

The igneous rocks in the Goseong area, the southwestern part of the Gyeongsang basin, are composed of the volcanic rocks, Bulgugsa granites and intrusive andesites. The volcanic rocks are andesitic lapilli tuff, dacite and rhyolite. The granites are mainly of hornblende-biotite granite and intruded into the sedimentary basement and the volcanic rocks. The intrusion of andesitic dyke is thought to be the latest igneous activity in the area. In the variation diagrams of the major oxides, the three igneous rock types show different variational trends, indicating that they were from the different magmatic pulses. K-Ar radiometric ages suggest that the igneous activity in the Goseong area had occurred during late Cretaceous period. The ages of the volcanic rocks seem likely to have become younger due to the thermal effect by the granitic intrusion. The major element compositoinal variation of the granites from the Goseong area are compared with those from the Jindong, Geoje and Masan areas. By the comparison, it is easily understood that the Jindong granites are fairly different from the other three granites. On the other hand, the Goseong, Geoje and Masan granites generally show similar variational trends with each other, suggesting that they are of similar genetic origin. Combining the similarity of the geochemical features and the difference of the intruding ages between the Goseong and Masan granites, it seems like that the magma generation from the same source materials had occurred at a temporal interval.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.263-270
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• 2007

Tunnel behavior measured by monitoring during construction is a main item for safety evaluation and it depends widely upon local geological characteristics. To assess in this study how much the geological factors influence on tunnel behavior for each RMR factor, a quantification analysis was carried out using tunnel face maps and measurements as explanatory variables and dependent variables, respectively. The results showed that average significance of the influence of RMR factors - R1, R2, R3, R4 and R5, on tunnel displacements are 17.0%, 20.4%, 20.4%, 11.6% and 30.6%, respectively, and this probably indicates that the groundwater condition played a significant role for the tunnel displacement.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.325-330
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• 2016

The second phase of low- and intermediate-level waste (LILW) disposal facility is under planned on the sedimentary rock in unsaturated zone. In this study, we created two meshes which were a matrix continuum mesh and a fracture continuum mesh to carry out 2 dimensional numerical modeling for groundwater flow in the unsaturated zone containing fractures focused on the second phase of LILW disposal facility. Two continuum meshes were developed using MINC in meshmaker module of TOUGH2 code. A fracture continuum mesh was included the k-field distribution of the permeability derived from the Discrete Fractured Network (DFN) modeling. To apply the unsaturated zone for the modeling, the gridding steps to generate mesh were developed. Each step to generate a mesh consisted of definition of materials, setting the initial conditions and creating grids using MINC. The methodology development of meshes in this study will be applied for more precise modeling of groundwater flow and mass transport.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.98-104
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• 2007

A survey was performed to evaluate the distribution of radon concentrations in groundwater of South Korea. Groundwaters of 615 wells were sampled for this study during the four years from 1999 to 2002. The results showed radon values ranging from 4 pCi/L to 40,010 pCi/L with a mean and a median of 1,862 pCi/L and 920 pCi/L, respectively. The samples were classified into five groups according to the rock types; granite, sedimentary rocks, metamorphic rocks, Ogcheon metamorphic rocks, and Cheju volcanics. Mean radon concentrations were highest (2,595 pCi/L) in granites and lowest (238 pCi/L) in Cheju volcanic rocks. The groundwaters generally showed the highest radon content (2,298 pCi/L) in the weathered and the fractured bedrock complex and the lowest level (672 pCi/L) in the alluvium. The results showed that the radon concentrations in South Korea are low relative to those reported from other countries. But further investigations are suggested to confirm our results.

• Journal of the Korean earth science society
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• v.26 no.6
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• pp.584-596
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• 2005

Morphology, surface sediments, sedimentation rates and sea-cliff erosion have been monitored, for one year to investigate the shoreline changes and tidal beach characteristics in Cheonsu Bay along the west coast of Korea. The seacliff of the bay consists of intensively weathered sedimentary rocks and soft soil, showing an erosion range of $-58.9\~73.3cm/yr$ by a weak wave forcing. Active sea-cliff erosions are recognized by peculiar geomorphic features, including saw teeth-shaped coastline, gravels, relict weathered basement-rock and 'Island Stack' exposed on the high-tide beach surface. The beach sediments show low compositional maturity at the south and north headlands and gradually high towards the central part. This observation seems to be caused by the fact that beach sediments are to originate from the both headlands in the study area and then transported by long-shore current associated with a wave action.

• Journal of the Korean earth science society
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• v.23 no.6
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• pp.507-513
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• 2002

To delineate the relationship between dynamic elastic modulus and lithologies, suspension PS logging was applied to Yuseong granite, Paldang banded gneiss, and Sabuk sedimentary rock. P and S wave velocities were also measured for these lithologies. In addition, uniaxial strength and Poisson’s ratio were measured in a laboratory for Yuseong granite and Paldang banded gneiss. In laboratory measurements, P and S wave velocities in Paldang banded gneiss were higher than those in Yuseong granite whereas Poisson’s ratio in Paldang banded gneiss was lower than that in Yuseong granite. This implies that P and S wave velocities correlate reversely with Poisson’s ratio. The dynamic Young modulus obtained from suspension PS logging was high compared to the dynamic bulk modulus and the dynamic shear modulus.