• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.85-95
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• 2007

It is difficult for seismic survey to get hold of characteristic of coal shale fractured zone and if coal shale zone did not come into contact with underground water, coal shale zone has characteristic of good strength. But in case coal shale zone is exposed by excavation or blasting to the air, strength of coal shale zone decreases in short term and weathering of coal shale zone progresses rapidly. Therefore, the prediction of tunnel collapse is not easy in the coal shale zone and the great portion of tunnel collapse takes place in a moment. From a view point of strength, after twelve hours form result of point load test strength of coal shale decreases by fifty six percent when coal shale zone come into contact with ground water. The standard reinforcement design of coal shale fractured zone was presented in the paper.

• Tunnel and Underground Space
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• v.10 no.4
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• pp.533-543
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• 2000

Deformation behavior and stability of vertical pipeline subjected to underground excavation have been studied by means of numerical analysis. Vortical ground displacements cause the pipe to be compressed, while horizontal ones cause it to be bent. In that region the vertical pipeline meets with the induced compressive stress and bending stress. In addition horizontal rock stress subjected to underground excavation may press the tube in its radial direction and it finally produces the tangential stress of pipe. In this study active gas well system is considered as an example of vertical pipelines. Factor analysis has been conducted which has great influence on the pipeline behavior. Three case studies are investigated which have the different pillar widths and gas well locations in pillar. For example, where overburden depth is 237.5 m and thickness of coal seam is 2.5 m, chain pillar of 45.8 m width in the 3-entry longwall system is proved to maintain safely the outer casing of gas welt which is made of API-55 steel, 10$\frac{3}{4}$ in. diameter and 0.4 in. thickness. Finally an active gas well which was broken by longwall mining is analyzed, where the induced shear stress turn out to exceed the allowable stress of steel.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.255-265
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• 2007

As the mechanism and effect range of subsidence are altered according to the various conditions (the ground condition, the earth pressure, the geometric condition of underground cavity and the structure load), the analysis and prediction of subsidence in abandoned mining area are very difficult. Also, as the geological characteristics and the mining methods are differed in each mines, the application of the pre-existing reinforcements without improvement has a lot of difficulties and limits. In this study, the various underground investigation such as long-depth core drilling, seismic tomography and BIPS (borehole image processing system) were performed, the distribution of underground cavity and coal seam and rock relaxation condition were analyzed. And we predicted the type of subsidence and estimated the subsidence by theories of mining subsidence. With these results, we analyzed the mechanism of subsidence occurrence in the research object area. Finally, we improved existing methods which were applied to the abandoned mining area and also we established the rational reinforcement for the ground and structure foundation against each subsidence cause.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.59-68
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• 1999

To clarify the geological structure of Yangsan fault around Sangchon-ri in the southern part of Kyungsang Basin the resistivity (dipole-dipole profiling) and VLF surveys carried out on the four profiles, crossing the inferred trace of the fault. The resistivity contrast across the fault is clearly shown on the profiles: higher resistivity and lower resistivity on the east and west, respectively. It is most likely from the uplift of the granitic bedrock on the east park due to the strike-fault raulting with vertical movement. The zero-crossing points of VLF anomalies, associated with near-surface fracture zone, are found to well correlate with the resistivity boundaries from the dipole-dipole profiling. Consequently, southern segment of Yangsan fault (at Sangchon-ri area) is interpreted to be vertically developed strike-slip fault with a difference more than 10m depth of basement rock at both sides.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.141-147
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• 1998

This study was initiated to identify the general groundwater quality and the effects of heavy-metal enrichments in the black shales and coal materials in Dukpyung area. Groundwater quality could be divided into three groups based on the major weathering processes in the groundwater system; Group I of carbonate weathering, Group II of silicate weathering with the probable effects of acidic mine drainage, and Group III of silicate weathering with relatively high concentrations of chloride components in anions. Metal contamination of groundwater was not observed. Locally, however, acidic mine drainage appeared to be produced and recharged into the groundwater system. In addition, contamination by NO$_3$-N ranged 2 to 3 times higher than the drinking water standards, probably due to infiltration of domestic sewage and/or fertilizers into the shallow aquifer.

• Tunnel and Underground Space
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• v.23 no.1
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• pp.31-41
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• 2013

Graphical method has been widely applied to the prediction of subsidence area, and is known to have advantages in analysis of trough subsidence which is common in horizontally seamed mine area. However, it is reported that most of the ore bodies in Korea are geologically inclined from sub-horizontal to steep, and therefore, the sinkhole subsidence is frequent in abandoned mine area. For these reasons, it is not to be desired that graphical method is applied for predicting the subsidence occurrence. This paper describes the results of subsidence zone prediction considering the dip direction and the opposite direction of inclined ore bodies from the case studies on the 163 subsidence occurrence regions. The results show also the assumed angle which can define the range of subsidence in the surface area. In conclusion, the limit of this angle is suggested after taking into account the comparison with graphical method and the application to the case histories.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.171-171
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• 2011

헬륨냉동계통은 연구용 원자로인 하나로에서 냉중성자를 생산할 수 있도록 설치된 수조내기기 내의 감속재인 수소가 정상적으로 열 사이펀을 유지하기 위한 주요 계통이다. 헬륨냉동계통은 헬륨가스를 압축하는 헬륨 압축부분과 헬륨가스를 팽창시켜 저온을 생성시키는 헬륨 팽창부분으로 나누어진다. 헬륨 압축부분은 두 개의 스크류가 맞물려 회전하면서 약 1.05 bar(a)의 헬륨가스를 최대 13 bar(a)까지 압축시키는 압축기가 있으며, 헬륨 팽창부분인 냉동박스의 팽창 터빈은 self-acting gas bearing에 의해 구동되며, 저온모드 운전 시작시 헬륨 압축부분에서 일부의 가스는 팽창 터빈 축(shaft)으로 유입되어 회전속도가 서서히 증가하면서 고속으로 회전하여 극저온의 헬륨가스(14~18 K)를 생성하는 주요 기기이다. 헬륨을 팽창하는 부분인 냉동박스 내로 헬륨 압축가스를 유입하기 전에 압축된 헬륨가스 내 불순물의 순도를 분석하여 냉동박스의 주요 부품인 팽창터빈의 운전에 영향을 미치지 않는 것이 가장 중요하다. 따라서 헬륨 저압측에 헬륨가스 내 불순물 즉, 수소($H_2$), 수분($H_2O$), 질소($N_2$), 탄화수소류(CxHy) 및 오일(Oilaerosol) 등의 함량을 분석하기위해 가스 분석기가 설치되어 있으며, 냉동박스 내로 유입되기 전에 헬륨압축에서 순환되는 가스 내 불순물인 수분, 질소, 탄화수소류 및 오일은 10 vpm 이하이어야 하며, 수소 함량은 0.1 % 이내이어야 한다. 헬륨 압축부분에서 순환되는 가스의 불순물이 요구 조건에 만족하도록 헬륨 고압측과 헬륨 저압측에 cryogenic adsorber를 설치하여 가스 내 불순물을 제거하는 가스순도제어 작업을 수행해야 한다. cryogenic adsorber를 사용하기 위해서는 장치 내의 불순 가스를 공정진공도(1.33 X $10^{-3}$ mbar) 이하로 진공배기하는 작업이 매우 중요하다. 이는 계통의 헬륨가스가 오염되지 않도록 하는 것으로 cryogenic adsorber 내에는 액체질소를 충전하여 액체질소 온도에 노출된 활성탄층을 헬륨가스가 흐르면서 수분, 질소, 탄화수소류 및 오일 등이 제거된다. 이 논문에서는 헬륨냉동계통의 가스 순도 제어 작업을 통해 헬륨가스의 순도가 요구조건 이하로 만족하며, 팽창 터빈의 운전에 영향을 미치지 않음을 기술하고자 한다.

• Korean Journal of Food Science and Technology
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• v.35 no.6
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• pp.1226-1232
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• 2003

Bamboo trees have been used for a long time as folk remedies for treatment of hypertension and stroke symptoms in Oriental regions. These pharmaceutical effects of bamboos look like to be related to its antioxidant capacity and phytochemicals in bamboos. To evaluate the antioxidative effects of bamboo trees, five kinds of bamboo varieties dominant in Korean peninsular were chosen and determined its total antioxidaive activities, free radical scavenging activities and nitrite scavenging activities by TEAC (Trolox Equivalent Antioxidant Capacity) assay, DPPH and Griess reagent assay using in vitro system, respectively. To evaluate the correlation between antioxidative activities and Maillard reaction during hot water extraction, contents of reducing sugar and total nitrogen and brown color intensity at 420 nm were determined. When total antioxidative activities, free radical scavenging activities and nitrite scavenging activities of five kinds of bamboo trees were compared, wang-dae (Phyllostachys bambusoides S. et Z.) showed the strongest effect among samples, although all kinds of extracts showed relatively strong effects against oxidation. The bamboo culms extract showed stronger antioxidative effects than that of bamboo leaves. In each fraction obtained from 70% ethanol extract, antioxidative effect were increased in order of dichloromethane>ethyl acetate>butanol>water>hexane fraction. In reducing sugar analysis of extracts, reducing sugar contents of water extracts were higher than that of 70% ethanol extracts and wang-dae water extract showed the highest level which was 708.92 mg/g. Total nitrogen contents of the extracts were $1.785{\sim}2.605\;mg%$ and contents in water extracts were lower than that in 70% ethanol extracts. Brown color intensity at 420 nm showed similar tendency with results in reducing sugar contents.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.3
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• pp.266-273
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• 1983

In a series of studies on the chemical compositions and properties of organic matter from peats, volcanic ash soils and paddy rice soils, a comparative study on the composition and the fractional distribution of nitrogenous organic matters were undertaken for the elucidation on their characteristics. The results obtained are summerized as follows. 1. Gimpo and Peongtaeg peats showed higher content of organic matter, more than 60%, than Gimje and Yeongdong peats, and there is a great difference between the two groups in total-N, CEC and ash content. 2. The content of Lignin, Hollocellulose and Hemicellulose in organic matter was 12-25%, 15-31% and 7-14% respectively, and Gimpo peats were lots of Lignin content compared to others. 3. Sixty seven to eighty eight percent of the total-N in the soil was hydrolysable by 6 N-HCl and they were decreased in the order of volcanic ash soils (86.4%), mineral paddy soils (77.2%) and peats (72.3%). 4. The fractionations of acid hydrolysable organic-N were ${\alpha}$-amino acid-N(25-45%), unidentified-N (12-50%), amino sugar-N (1-7%) and ammonium-N (12-25%). 5. Almost same pattern in the amino acid composition of the acid hydrolysates of peat and soil organic matter was showed in the thin-layer chromatogram.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.473-490
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• 2007

Strata of the Kachi-1 well, Kunsan Basin, offshore western Korea, were analyzed by using integrated stratigraphy approach. As a result, five distinct unconformity-bounded units are recognized in the well: Triassic, Late Jurassic-Early Cretaceous, Early Cretaceous, Late Cretaceous, and Middle Miocene units. Each unit represents a tectono-stratigraphic unit that provides time-sliced information on basin-forming tectonics, sedimentation, and basin-modifying tectonics of the Kunsan Basin. In the late Late Jurassic, development of second- or third-order wrench faults along the Tan-Lu fault system probably initiated a series of small-scale strike-slip extensional basins. Continued sinistral movement of these wrench faults until the Late Cretaceous caused a mega-shear in the basin, forming a large-scale pull-apart basin. However, in the Early Tertiary, the Indian Plate began to collide with the Eurasian Plate, forming a mega-suture zone. This orogenic event, namely the Himalayan Orogeny, continued by late Eocene and was probably responsible for initiation of right-lateral motion of the Tan-Lu fault system. The right-lateral strike-slip movement of the Tan-Lu fault caused the tectonic inversion of the Kunsan Basin. Thus, the late Eocene to Oligocene was the main period of severe tectonic modification of the basin. After the Oligocene, the Kunsan Basin has maintained thermal subsidence up to the present with short periods of marine transgressions extending into the land part of the present basin.