• The Journal of Engineering Geology
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• v.24 no.2
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• pp.201-215
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• 2014

This study was performed to investigate the correlation between hydraulic conductivity and the flow rate of an aquifer, with the flow rate calculated from the laterals of the radial collector well using data obtained by the development project of riverbank filtration (Second Phase) in Changwon City. The hydraulic conductivity was empirically calculated from unconsolidated sediments collected from a sandy gravel layer along the middle-to-downstream sections of the Nakdong River. The Beyer equation produced the most suitable hydraulic conductivity from the various empirical formulas employed. The calculated hydraulic conductivity ranged from 0.083 to 0.264 cm/s, with an average value of 0.159 cm/s, suggesting that the aquifer in the study area possesses a high permeability with a good distribution of sandy gravel. The relationship between the calculated hydraulic conductivity in the aquifer and the entrance velocity into the screen, the flow rate was analyzed through the linear regression analysis. From the result of regression analysis, it showed that the hydraulic conductivity and the entrance velocity into the screen and the flow rate have a linear regression equation having about 72% of the high correlation. The result of verification in the measured data between each variable showed a high suitability from being consistent with the approximately 72% in the linear regression analysis. This study demonstrates that the groundwater flow rate can be estimated within the laterals of the radial collector well using a linear regression equation, if the hydraulic conductivity of the aquifer is known. This methodology could thus be applicable to other aquifers with hydraulic conductivity and permeability parameters similar to those in the present study area.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.573-586
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• 2019

A seismic hazard map based on spatial analysis of various sources of geologic seismic information was developed and assessed for regional seismic vulnerability in South Korea. The indicators for assessment were selected in consideration of the geological characteristics affecting the seismic damage. Probabilistic seismic hazard and fault information were used to be associated with the seismic activity hazard and bedrock depth related with the seismic damage hazard was also included. Each indicator was constructed of spatial information using GIS and geostatistical techniques such as ordinary kriging, line density mapping and simple kriging with local varying means. Three spatial information constructed were integrated by assigning weights according to the research purpose, data resolution and accuracy. In the case of probabilistic seismic hazard and fault line density, since the data uncertainty was relatively high, only the trend was intended to be reflected firstly. Finally, the seismic activity hazard was calculated and then integrated with the bedrock depth distribution as seismic damage hazard indicator. As a result, a seismic hazard map was proposed based on the analysis of three spatial data and the southeast and northwest regions of South Korea were assessed as having high seismic hazard. The results of this study are expected to be used as basic data for constructing seismic risk management systems to minimize earthquake disasters.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.107-127
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• 2003

After detailed geological mapping, structural and fracture-density data were collected and analyzed in the vicinity of Cheonseong and Jeongjok Mts., Gyeongsangnam-do. A extensive dextral strike-slip fault (Beopgi Fault) Parallel to Yangsan and Dongrae Faults, a dextral-transtensional-NW fault, and a few intermittent faults have been found in the study area. Based on strike and frequency, fracture system has been divided into three sets such as NNE-trending J1 ($NS-40^{\circ}E$), WNW-trending J2 ($N50^{\circ}-80^{\circ}W$), and ENE-trending J3 ($N60^{\circ}-90^{\circ}E$). According to analysis of fracture density, it is revealed as follows: (a) Jl is the combination of Y-, P-, and R-shear fractures due to the dextral strike-slip of the Beopgi Fault. (b) J2 is the preexisted fracture zone conducting the intrusion of granite. Two tensional fractures dipping to NNE and SSW respectively have been induced by intrusion of granite and followed crustal uplift. (c) J3 is the tensional fracture developed between Yangsan and Dongrae Faults having NNE trend and dextral strike-slip sense. This study aims to reduce environmental impact and insure stability of underground facilities and tunnels.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.940-948
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• 2006

Fluorescence measurements of dissolved organic matter(DOM) have the superior advantages over other analysis tools for applying to water quality management. They are simple and fast and require minimal pretreatment of samples. Fluorescence index($F_{450}/F_{500}$), synchronous spectra, and fluorescence excitation-emission matrices(EEM) of various DOM samples were investigated to discriminate autochthonous/allochthonous composition, protein-like fluorescence, fulvic-like fluorescence, humic-like fluorescence, terestrial humic-like fluorescence by comparing among the real DOM samples of different origins with the help of literature. The samples used included standard purified DOM, lake, river and wastewater treatment effluent. The relative distribution of various DOM composition was derived from the ratios of each fluorescence region. The results were very consistent with those expected from the sample properties. Allochthonous and terrestrial humic-like fluorescence were more prominent in the samples with abundant soil-derived DOM components. In addition, the protein-like fluorescence property was more pronounced in the samples where strong algal or microbial activities were expected. It was also shown that the ratio of protein-like/terrestrial humic-like fluorescence obtained from synchronous spectrum and fluorescence EEM could be used as an indicator for the evaluation of wastewater treatment on the downstream water quality of rivers and for the prediction of the degree of algal/microbial activities in lakes. It is expected that the results of this study will provide the basic information to develop the future water quality management techniques using DOM fluorescence measurements.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.1-11
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• 2001

The geological characteristics of Korea are that we can encounter the rock layer only after 10m of excavation, methods to presume the rock pressure distribution of the rock layer is urgently needed. When using the existing empiric science of Terzaghi-Peck, Tschebotarioff to measure the rock pressure of the rock layer, underestimate the real strength because of the cohesion is ignored. Therefore calculating the horizontal sliding force of wedge block, which includes the dips and shear strength of discontinuities and surcharge load etc., think to be to getting a closer rock stress of the real rock pressure acting upon the earth structure in rock mass. This research use Coulomb soil pressure theory assuming that the backfill soil will yield wedge failure when it has cohesion, applying Prakash-Saran(l963), and then it uses equilibrium of force and shear strength $\tau$=c+$\sigma$tan $\Phi$ of the cliscontinuities. Analyzing shear strength and dips of cliscontinuities using calculated theory according to the status of discontinuities aperture, we were able to find out that because the cohesion and friction angle of the rock layer itself is large enough, how the dip directions and dips facing the excavation face is the only factor deciding whether or not the rock stress is applied. The evaluated theory of this research should be strictly estimated, so that the many parameters such as c, $\Phi$value, types and structures of rock class, excessive lateral pressure, dynamic load, earthquake, needed later when calculating shear strength of discontinuities and especially the ground water effect acting on rock layer should be coumpted with many measuring data achieve at the insite to study the application.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.71-78
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• 2016

This study aimed to evaluate the occurrence of natural radionuclides in Korean groundwater. Groundwater radionuclide data for the period 2000-2011 were obtained from the National Institute of Environmental Research and published literature, classified into five groups according to host rock type, and used to construct detailed concentration maps. Radon, uranium, gross-α, and radium concentrations ranged from 0.4 to 64,688.0 pCi/L (mean: 4,907 pCi/L), 0 to 2,297 μg/L (mean: 27.5 μg/L), 0 to 312 pCi/L (mean: 3.9 pCi/L), and 0 to 17.4 pCi/L (mean: 0.2 pCi/L), respectively. Radon concentrations in 562 of a total 1,501 wells (i.e., 53.5%) exceeded 4,000 pCi/L, which is the acceptable contamination threshold established by the United States Environmental Protection Agency. Uranium, gross-α, and radium concentrations exceeded the respective thresholds of 30 μg/L, 15 pCi/L, and 5 pCi/L in 121 of 1,031 wells (11.9%), 34 of 978 wells (3.5%), and 4 of 89 wells (4.5%), respectively. The mean radionuclide concentration in groundwaters hosted by igneous and metamorphic rocks was higher than that in groundwaters hosted by other rock types, such as volcanics, carbonates, and other sedimentary rocks. The correlations between individual radionuclides were weak or insignificant.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.101-115
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• 2016

We carried out laboratory material tests on two cements (KS-1 ordinary Portland and Class G) with changing W/S (Water/Solid) and the content of fly ash in order to evaluate their physical and mechanical properties. The specimens of KS-1 ordinary Portland cement were prepared with varying W/S (Solid=cement) in weight, while those of Class G cement were prepared with changing the content of fly ash in volume but maintaining W/S (Solid=cement+fly ash). The results of the material tests show that as the W/S in KS-1 ordinary Portland cement and the content of fly ash in Class G cement increase, the properties (density, sonic wave velocity, elastic constants, compressive and tensile strengths, thermal conductivity) decrease, but porosity and specific heat increase. In addition, an increase in confining pressure and in the content of fly ash leads to plastic failure behavior of the cements. The laboratory data were then used in a stability analysis of cement sheath for which an analytical solution for computing the stress distribution induced around a cased, cemented well was employed. The analysis was carried out with varying the injection well parameters such as thickness of casing and cement, injection pressure, dip and dip direction of injection well, and depth of injection well. The analysis results show that cement sheath is stable in the cases of relatively lower injection pressures and inclined and horizontal wells. However, in the other cases, it is damaged by mainly tensile failure.

• Economic and Environmental Geology
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• v.27 no.1
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• pp.65-80
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• 1994

The Tertiary $Ch{\check{o}}ngja$ basin is located in the southeastern coastal area of the Korean Peninsula. It is a lozenge shaped fault-bounded basin with circa $5{\times}5km$ areal extent, isolated from other Tertiary basins by the Cretaceous Ulsan Formation in-between. The northwestern boundary of the basin is a domino/listric type normal fault trending $N30^{\circ}E$, whereas its southwestern boundary is a dextral strike-slip fault (trending $N20^{\circ}W$) with a lateral offset of more than 1 km. The basin is bounded by the East Sea on the eastern margin. Basin-fills consist of extrusive volcanic rock (Tangsa Andesites) of Early Miocene (16~22 Ma in radiometric age), unconsolidated fluviatile conglomerate (Kangdong Formation) and shallow brackish-water sandstone ($Sinhy{\check{o}}n$ Formation). The latter yields abundant Vicarya-Anadara molluscan fossils of early Middle Miocene age. The Tertiary strata become younger toward the northwestern boundary-fault of the basin, showing a zonal distribution pattern parallel to the fault: the younger sedimentary formations occupy a narrow zone of 2 km width along the northwestern boundary-fault, whereas the older Tangsa Andesites underlie them unconformably in the eastern and southeastern portions of the basin. The strata in the basin, including the Tangsa Andesites, are tilted (about $20^{\circ}$) toward the northwestern boundary-fault Sedimentary strata thicken toward the boundary-fault, forming a wedge shaped half-graben structure. A number of small-scale syndepositional normal growth faults and graben structures are observed in the sedimentary strata. These extensional structures have the same trend as the normal northwestern boundary-fault which we interpret as a pull-apart detachment fault. These characteristics imply persistent extension during the basin evolution, caused by a NW-SE directed tensional force. The $Ch{\check{o}}ngja$ basin is, thus, a kind of syndepositional tectonic basin evolved in a strike-slip (pull-apart) regime. The latter was caused by a dextral simple shear associated with the NNW-SSE opening of the East Sea. In view of the fact that the normal growth faults do not cut through the uppermost portion of the youngest $Sinhy{\check{o}}n$ Formation, it is inferred that the tensional force came to be inactive in the early Middle Miocene. This is coincident in timing with the termination of the East Sea opening (15 Ma).

• The Journal of Engineering Geology
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• v.21 no.3
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• pp.259-269
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• 2011

Concentrations of uranium (U) and radon (Rn) were measured in groundwater from 74 wells in the Icheon area, with the aim of determining the range and distribution of concentrations in an area underlain by granite (in this case, the Icheon granite). U concentrations ranged from 0.02 to 1,640.0 ${\mu}g/L$ (median value, 2.03 ${\mu}g/L$) and Rn concentrations ranged from 40 to 23,400 pCi/L (median value, 4,649 pCi/L). U concentrations in 10.8% of the samples exceeded 30 ${\mu}g/L$, which is the maximum contaminant level (MCL) proposed by the US Environmental Protection agency (EPA), based on the chemical toxicity of U. In addition, U concentrations in 59.5% and 13.5% of the samples exceeded 4,000 pCi/L (the Alternative MCL (AMCL) of the US EPA) and 8,100 pCi/L (Finland’s guideline level), respectively. We found no significant correlations between U (Rn) and other constituents, except for U-$HCO_3$ (correlation coefficient of 0.71), U-Ca (0.69), U-Li (0.45), U-Sr (0.43), and U-F (0.42). U and Rn contents in the groundwater are low relative to those in areas in other countries with similar geological settings, possibly due to the inflow of shallow groundwater to the wells in the Icheon area.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.37-48
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• 2010

The purpose of this paper is to evaluate how the rainfall field effect on a runoff simulation using grid radar rainfall data and ground gauge rainfall. The Gwangdeoksan radar and ground-gauge rainfall data were used to estimate a spatial rainfall field, and a hydrologic model was used to evaluate whether the rainfall fields created by each method reproduced a realistically valid spatial and temporal distribution. Pilot basin in this paper was the Naerin stream located in Inje-gun, Gangwondo, 250m grid scale digital elevation data, land cover maps, and soil maps were used to estimate geological parameters for the hydrologic model. For the rainfall input data, quantitative precipitation estimation(QPE), adjusted radar rainfall, and gauge rainfall was used, and then compared with the observed runoff by inputting it into a $Vflo^{TM}$ model. As a result of the simulation, the quantitative precipitation estimation and the ground rainfall were underestimated when compared to the observed runoff, while the adjusted radar rainfall showed a similar runoff simulation with the actual observed runoff. From these results, we suggested that when weather radars and ground rainfall data are combined, they have a greater hydrological usability as input data for a hydrological model than when just radar rainfall or ground rainfall is used separately.