• The Journal of the Petrological Society of Korea
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• v.28 no.2
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• pp.53-69
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• 2019

In the Jirisan area of the Yeongnam Massif, Korea, several ductile shear zones are developed within Precambrian gneiss complex (Jirisan metamorphic rock complex). The ductile shear zones have a general NS- and NNE-striking foliation with westward dipping directions. The foliation developed in the shear zones cut the foliation in gneiss complex. The stretching lineations are well developed in the foliated plane of the shear zone, showing ENE-trend with gentle plunging angle to the ESE direction. Within shear zone, several millimetric to centimetric size of porphyroclasts are deformed strongly as a sigmoid form by ductile shearing. The sigmoid patterns of porphyroclasts in the shear zones indicate the dextral shearing. The spatial distribution of ductile shear zone is characterized by the dominant NS- and NNE-striking dextral sense in the central and eastern regions respectively. In the western part, it develops in NE-striking dextral sense which is the general direction of the Honam shear zone. The U-Pb concordant ages obtained from the two samples, the strongly sheared leucocratic gneiss, are $1,868{\pm}3.8Ma$ and $1,867{\pm}4.0Ma$, respectively, which are consistent with the U-Pb ages reported around the study area. We supposed that the ductile shearing in the study area is occurred about 230~220 Ma during late stage of the continental collision around Korea and is preceded by granitic intrusion related to subduction during 260~230 Ma, which are supported by compiling the age data from sheared gneiss, deformed mafic dyke intruded gneiss complex, and non-deformed igneous rocks.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.491-505
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• 2018

As an alternative to deep geological disposal technology, which is considered as a reference concept, the domestic applicability of deep borehole disposal technology for high level radioactive waste, including spent fuel, has been preliminarily evaluated. Usually, the environment of deep borehole disposal, at a depth of 3 to 5 km, has more stable geological and geo-hydrological conditions. For this purpose, the characteristics of rock distribution in the domestic area were analyzed and drilling and investigation technologies for deep boreholes with large diameter were evaluated. Based on the results of these analyses, design criteria and requirements for the deep borehole disposal system were reviewed, and preliminary reference concept for a deep borehole disposal system, including disposal container and sealing system meeting the criteria and requirements, was developed. Subsequently, various performance assessments, including thermal stability analysis of the system and simulation of the disposal process, were performed in a 3D graphic disposal environment. With these analysis results, the preliminary evaluation of the domestic applicability of the deep borehole disposal system was performed from various points of view. In summary, due to disposal depth and simplicity, the deep borehole disposal system should bring many safety and economic benefits. However, to reduce uncertainty and to obtain the assent of the regulatory authority, an in-situ demonstration of this technology should be carried out. The current results can be used as input to establish a national high-level radioactive waste management policy. In addition, they may be provided as basic information necessary for stakeholders interested in deep borehole disposal technology.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.71-78
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• 2011

This paper aims to present the evaluation of engineering characteristics and reusing possibility of waste powders produced in dolomite and limestone nonmetal mining by physical and mechanical experiments on compaction, uniaxial compressive strength, permeability, chemical composition, and so on. Granite soil, 2 types of limestone waste powder, and 1 type of dolomite waste powder were used for main materials, and cement and bentonite were used for admixed materials in this experiments. The findings based on the experimental results are the severe difference of chemical composition of the dolomite & limestone waste powder and the crushed rock waste powder, and the outstanding of engineering characteristics of the dolomite waste powder with high content of MgO compared with the limestone waste powder. The engineering properties on compaction, uniaxial compressive strength, and permeability are enhanced with increase of admixed ratio of waste powder on granite soil. From the experimental results, it can be suggested that the dolomite waste powder admixed with in-situ granite soil is useful as geo-materials with considering of distribution costs.

• Journal of the Korean Geotechnical Society
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• v.37 no.1
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• pp.29-41
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• 2021

Although underground works are essential to use underground spaces in urban areas efficiently, various damages caused by constructions have often occurred, making them major social problems. Since 2018, it is stipulated in the Special Act on Underground Safety Management that appropriate construction methods must be used in the design stage to prevent various damage cases. This Special Act includes establishing an area subject to underground safety impact assessment, analysis of ground and geological status, review of effects caused by changes in groundwater, review of ground safety, and establishment of measures to secure underground safety. This study area consists of various strata in order of landfill, sedimentary silt, sedimentary sand, sedimentary gravel, weathering zone, and foundation rock. Also, the slurry wall, a highly rigid underground continuous wall, was chosen as a construction method to consider high water table distribution and minimize the influence of the surroundings in this area. However, ground subsidence occurred on the road nearby in December 2019 due to the inflow of loosening soil to the construction area. Thus, several types of site investigations were conducted to suggest an appropriate analysis method and to find out loosed ground behavior and its area for the subsided site. As a result, new design soil properties were re-calculated, and the reinforcement measures were proposed through analytical verification.

• The Journal of the Korea Contents Association
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• v.21 no.8
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• pp.49-59
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• 2021

Since ancient times, legends and tales have been handed down with a spirituality, shamanistic meaning, and imagination. Among many tales about people and animal footprints that are handed down in various parts of Korea, Changnyeong's 'Munhojang Footprint' is the first case in which the physical evidence(footprints) that the main character has left was identified as a dinosaur footprint. In this study, we performed a scientific analysis based on the basic data collection, distribution pattern of 'Munhojang Footprint', three-dimensional digital recording and visualization, as well as case analysis and humanitic review of footprints in tales and legends. The Munhojang Footprints has long been known as human footprints left in the natural rock due to its shape and preservation status. A new analysis that the Munhojang footprints (composed of 13 footprints) are dinosaur tracks shows social perceptions of the ancient people, characterized by the fear of supernatural beings and the limits of scientific interpretation. Through this scientific and humanistic exploration of Munhojang Footprint that are passed down from generation to generation as legends, pray for peace and well-being of the village through rituals and rituals every year, and have been preserved and managed as practical evidence, it is expected that traditional culture and natural heritage will be linked and mutual value will be enhanced.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.743-752
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• 2021

The three-dimensional distribution of the fault was evaluated using gravity field interpretation such as curvature analysis and Euler deconvolution in the Seoul-Gyeonggi region where the Chugaryeong fault zone was developed. In addition, earthquakes that occurred after 2000 and the location of faults were compared. In Bouguer anomaly of Chugaryeong faults, the Pocheon Fault is an approximately 100 km fault that is extended from the northern part of Gyeonggi Province to the west coast through the central part of Seoul. Considering the frequency of epicenters is high, there is a possibility of an active fault. The Wangsukcheon Fault is divided into the northeast and southwest parts of Seoul, but it shows that the fault is connected underground in the bouguer anomaly. The magnitude 3.0 earthquake that occurred in Siheung city in 2010 occurred in an anticipated fault (aF) that developed in the north-south direction. In the western region of the Dongducheon Fault (≒5,500 m), the density boundary of the rock mass is deeper than that in the eastern region (≒4,000 m), suggesting that the tectonic movements of the western and eastern regions of the Dongducheon Fault is different. The maximum depth of the fracture zone developed in the Dongducheon Fault is about 6,500 m, and it is the deepest in the research area. It is estimated that the fracture zone extends to a depth of about 6,000 m for the Pocheon Fault, about 5,000 m for the Wangsukcheon Fault, and about 6,000 m for the Gyeonggang Fault.

• Economic and Environmental Geology
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• v.55 no.2
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• pp.197-207
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• 2022

This study investigated spectroscopic exploration of Myeonsan formation, the titanium(Ti) ore hostrock, in Joseon supergroup based on machine learning technique. The mineral composition, Ti concentration, spectral characteristics of Myeonsan and non-Myeonsan formation of Joseon supergroup were analyzed. The Myeonsan formation contains relatively larger quantity of opaque minerals along with quartz and clay minerals. The PXRF analysis revealed that the Ti concentration of Myeosan formation is at least 10 times larger than the other formations with bi-modal distribution. The bi-modal concentration is caused by high Ti concentrated sandy layer and relatively lower Ti concentrated muddy layer. The spectral characteristics of Myeonsan formation is manifested by Fe oxides at near infrared and clay minerals at shortwave infrared bands. The Ti exploration is expected to be more effective on detection of hostrock rather than Ti ore because ilmenite does not have characteristic spectral features. The random-forest machine learning classification detected the Myeonsan fomation at 85% accuracy with overall accuracy of 97%, where spectral features of iron oxides and clay minerals played an important role. It indicates that spectral analysis can detect the Ti host rock effectively, and can contribute for UAV based remote sensing for Ti exploration.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.31-40
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• 2022

This study compares elastic moduli calculated using two stiffness testing methods with different strain ranges to evaluate the stress-settlement characteristics of foundation support layers. Elastic moduli were calculated by the soil stiffness gauge (SSG) in the micro-strain range and the plate load test (PLT) in the medium strain range. To apply the elastic moduli obtained by the two testing methods with different strain ranges to the design and construction of foundation soils, the correlation between each measurement value should be identified in advance. As a result of the comparative analysis of the elastic moduli calculated using the two methods in weathered soil and rock, which are representative support layers in Korea, the calculated elastic moduli differed depending on the types of soil and stress conditions. For various soil types, the static elastic modulus obtained by the PLT was reduced by 56% because of the difference in the strain level of the test compared with the dynamic elastic modulus obtained by the SSG. Therefore, the results show that it is necessary to apply corrections to the stress distribution, stress level, and dynamic effect according to the ground stiffness to effectively use the SSG instead of the PLT.

• Journal of Conservation Science
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• v.37 no.6
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• pp.778-790
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• 2021

The Stone Seated Buddha Triad and Stone Standing Buddha in Bijung-ri are state-designated heritage (treasure) statues having the Buddha style of the Goryeo dynasty from the 6th century. Conservation scientific investigations were conducted to understand the preservation status of these stone Buddha statues and to establish a conservation plan. The Stone Seated Buddha Triad and Stone Standing Buddha are composed of fine-medium grained biotite granite, which is considered to be of the same origin owing to their low magnetic susceptibility distribution of less than 0.2 (×10^-3 SI unit) and similar mineral characteristics. The Stone Seated Buddha Triad has highly homogenous mineral composition and particle size, whole-rock magnetic susceptibility, and geochemical characteristics very similar to those of the nearby outcrop. It was confirmed that a combination of physical, chemical, and biological factors affects the Stone Buddha statues. In particular, both the Stone Seated Buddha Triad and Stone Standing Buddha tend to be chipped off from the front and cracked and scaled from the back. The Stone Standing Buddha located outdoors experiences granularity decomposition and black algae formation, which accelerate the weathering under unfavorable conservation environments. The result of non-destructive physical property diagnosis using ultrasonic velocity showed that both the Stone Seated Buddha Triad and Stone Standing Buddha have been completely weathered (CW), indicating very poor physical properties.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.45-65
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• 2022

In this paper, a diaphragm wall that supports soils and rock was modeled using FLAC, a finite difference analysis program, to evaluate the seismic behavior of temporary retaining structures in a deep excavation. The appropriateness of the numerical model was verified by comparing its results with those of the centrifuge test performed in a similar condition. The bending moment distribution along the diaphragm wall shows a very similar tendency, and the maximum acceleration obtained at the backfill and top of the wall shows a difference within 5%. Based on the developed model, a parametric study was conducted in various input earthquake, ground, and excavation conditions. The maximum structural forces and bending moment under earthquake loading were compared with the maximum values during excavation, from which the critical condition that requires a seismic design was roughly sorted out. The maximum bending moment of a wall that retains soil layers increased 17%. Particularly, the axial force of struts located in loose soils increased 32% under 100 years return period of an earthquake event, which strongly is estimated to require seismic design for structural safety.