• Economic and Environmental Geology
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• v.36 no.2
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• pp.123-131
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• 2003

Geophysical surveys(electrical resistivity, self-potential, seismic refraction, GPR) were conducted to investigate the physical properties of the subsurface, and to delineate the flow channel of leachate from a AMD(acid mine drainage), buried rock wastes and tailings, and drainage pipes at an abandoned mine(Kwangyang mine). Especially in rainy season the sites appear to be abundant in AMD leachate, characterized by electrical conductivities of 0.98-1.10 ms/S. Electrical resistivity sections indicate that the leachate flows running in two directions at southern part rise up through the narrow fracture zones at the central part and contaminates the surrounding soil and stream. Such schematic features at the anomalous zone are well correlated with negative peaks in self-potential data, the limited penetration depth in GPR data and low velocity zone in seismic refraction data. Shallow high-resistivity zone is associated with the buried rock wastes which cause the diffractions in GPR image. In addition, the events at depth of approximately 1-1.25 m in GPR sections must be the metal pipes through which AMD is drained off to the inner bay.

• Economic and Environmental Geology
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• v.36 no.2
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• pp.59-74
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• 2003

Prospecting for energy and mineral resources is essential kind of public fundamentals that manage the nation's economy. Most explorations in the past were concentrated in the simple structural traps in relatively shallow depth. Due to their vast exploitation, recent history has shown that the emphasis in explorations has steadily shifted toward the subtle stratigraphic traps in deeper level. Increasing exploration for the subtle stratigraphic traps in deeper level requires precise correlation and assessment of deeply buried strata in the basin. However, the descriptive strati-graphic principles used for evaluation of the simple structural traps are limited to delineate the subtle stratigraphic traps in deeper depth. As this occurs. it is imperative to establish a new stratigraphic paradigm that allows a more sophisticated understanding on the basin stratigraphy. This study provides an exemplary application of integrated stratigraphic approach to defining basin history of the Middle Ordovician Taebacksan Basin, Korea. The integrated stratigraphic approach gives much better insight to unravel the stratigraphic response to tectonic evolution of the basins, which can be utilized fer enhancing the efficiency of resources exploration and development in the basins. Thus, the integrated stratigraphic approach should be emphasized as a new stratigraphic norm that can improve the probability of success in any type of resources exploration and development project.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.189-199
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• 2015

Our country's leading granite weathered soil of the ground slope failures that occur in cutting slope most cases, it does not require in-depth to the shear strength most of the surface layer is affected by weathering (1~2 m) at a shallow depth close to the ground, it is important to identify the reliability. Based on the result obtained in actual field investigation, the field slope type was classified by each type of wedge slope, Infinite slope, finite slope -I and finite slope -II, and the slope stability was examined respectively. In addition, using the numerical analysis results, the relationship between the slope inclination angle and safety factor was analyzed and it tried to offer basic data to which the stability in the field slope was able to be estimated by analyzing the safety factor change of the slope according to the slope type. In this study, classified into four types of natural slope, safety factor estimation method by slope types is proposed through the numerical analysis. However, some limit exists in generalizing in this research because it does not test various case studies. Therefore, the case study of a wide range of various sypes to assess the safety of various types slope can be made, accommodate a wide range of field conditions reasonable risk evaluation criteria may be derived.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.75-87
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• 2007

The recognitions of geometrical characteristics and occurrence conditions are very important to evaluate the land-slides in natural terrains. In this paper, the geometrical characteristics of landslides are analyzed according to a geo-logical condition in three landslides areas. The three landslides areas are classified to the geological condition. The three landslides areas are Jangheung, Sangju and Pohang. The geology of Jangheung area, Sangju area and Pohang area is gneiss, granite, and the tertiary sedimentary rock, respectively. During a heavy rainfall of $150{\sim}588mm$ in these areas, 1,582 landslides have occurred in 1998. The geometrical characteristics according to the geological condition analyzed from the investigation of these landslides. The frequency of landslide is high exceedingly above 90% of a slope attitude, while the frequency is very low below 70%. The frequency of landslide is high exceedingly between $26^{\circ}$ and $30^{\circ}$ of slope angle, while the frequency is very low below $20^{\circ}$. The size of the landslides is ranged from several tens to several hundreds The length is ranged from 5 m to 300 m, and the width is ranged from 3 m to 50 m. Also, the depth is less than 1 m. Therefore, the landslides in these areas have small width, long length and shallow depth. The type of the landslides is changed from transitional slide at the scarp to debris flow at the low part of slope.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.615-624
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• 2016

In this study, two rectangular barges in close proximity were simulated to analyze the characteristics of motion responses due to hydrodynamic interactions. Using a numerical solution from DNV-GL SESAM, coupled stiffness matrix terms for these same FEM models were added to the multiple body modes in the surge direction. Potential theory was used to calculate the first order radiation and diffraction effects on the simulated barge models. In the results, the sheltering effect of the barges was not shown at 1.3 rad/s with hull separation of 20 m in transverse waves. The separation effect between the barges was more clear with longitudinal waves and a shallow water depth. However, sway forces were influenced by hull separation with transverse waves. The peaks for sway and heave motion and sway force occurred at higher frequencies as hull separation narrowed with longitudinal and transverse waves. Given a depth of 10 m, the sway motion on the lee side of a coupled barge made a significant difference in the range of 0.2-0.8 rad/s with transverse and oblique waves. Also, the peaks for sway force were situated at lower frequencies, even when incident waves changed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.4
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• pp.109-119
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• 1998

Recently pipe-framed greenhouses are widely constructed on domestic farm area. These greenhouses are extremely light-weighted structures and so are easily damaged under strong wind due to the lack of uplift resistance of foundation piles. This experiment was carried out by laboratory soil tank to investigate the displacement be haviors of cylindrical pile foundations according to the uplift loads. Tested soils were sampled from two different greenhouse areas. The treatment for each soil type are consisted of 3 different soil moisture conditions, 2 different soil depths, and 3 different soil compaction ratios. Each test was designed to be repeated 2 times and additional tests were carried out when needed. The results are summarized as follows : 1. When the soil moisture content are low and/or pile foundations are buried relatively shallow, ultimate uplift capacity of foundation soil was generated just after begining of uplift displacement. But under the high moisture conditions and/or deeply buried depth, ultimate up-lift capacity of foundation soil was generated before the begining of uplift displacement. 2. For the case of soil S$_1$, the ultimate uplift capacity of piles depending on moisture contents was found to be highest in optimum moisture condition and in the order of air dryed and saturated moisture contents. But for the case of soil S$_2$, the ultimate uplift capacity was found to be highest in optimum moisture condition and in the order of saturated and air dryed moisture contents. 3. Ultimate uplift capacities are varied depending on the pile foundation soil moisture conditions. Under the conditions of optimum soil moisture contents with 60cm soil depth, the ultimate uplift capacity of pile foundation in compaction ratio of 80%, 85%, and 90% for soil 51 are 76kg, 115kg, and 155kg, respectively, and for soil S$_2$are 36kg, 60kg, and 92kg, respectively. But considering that typical greenhouse uplift failure be occurred under saturnted soil moisture content which prevails during high wind storm accompanying heavy rain, pile foundation is required to be designed under the soil condition of saturated moisture content. 4. Approximated safe wind velosities estimated for soil sample S$_1$and S$_2$are 32.92m/s and 26.58m/s respectively under the optimum soil condition of 90% compaction ratio and optimum moisture content. But considering the uplift failure pattern under saturated moisture contents which are typical situations of high wind accompanying heavy rain, the safe wind velosities for soil sample S$_1$and S$_2$are not any higher than 20.33m/s and 22.69m/s respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.211-224
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• 2018

It is important to design tunnel support system considering the various loads acting on the tunnel because they have a direct impact on the stability of tunnels. In Korea, standardized support patterns are defined based on the rock mass classification system depending on the project, and it is stated that it should be modified appropriately considering the behavior of tunnel during construction. In this study, the tunnel support pattern optimization method is suggested based on the convergence-confinement method, earth pressure, axial force of rock bolt, and moment acting on the shotcrete. The length and spacing of the rock bolts and the thickness of the shotcrete were optimized by using the differential evolution algorithm (DEA) and the results were compared to the standard support pattern III for railway tunnel. Rock bolt length can be reduced and the installation interval can be widened for shallow tunnel. As the depth of tunnel increases, the thickness of shotcrete increases linearly. Therefore, the thickness of shotcrete should be thicker than the standard support pattern as the depth of tunnel increases to secure the stability of tunnel.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2002.10a
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• pp.119-136
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• 2002

Contrasts in the style of the gold-silver mineralization in geologic and tectonic settings in Korea, together with radiometric age data, reflect the genetically different nature of hydrothermal activities, coinciding with the emplacement age and depth of Mesozoic magmatic activities. It represents a clear distinction between the plutonic settings of the Jurassic Daebo orogeny and the subvolcanic environments of the Cretaceous Bulgugsa igneous activities. During the Daebo igneous activities (c.a. 200-150 (?) Ma) coincident with orogenic time, gold mineralization took place between c.a. 195 and 135 (127 ?) Ma. The Jurassic Au deposits commonly show several characteristics; prominent association with pegmatites, low Ag/hu ratios in the ore-concentrating parts, massive vein morphology and a distinctively simple mineralogy including Fe-rich sphalerite, galena, chalcopyrite, arsenopyrite, Au-rich electrum, pyrrhotite and/or pyrite. During the Bulgugsa igneous activities $(110\~50Ma)$, the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high AE/AU ratios in the ore concentrates, and diversity of ore minerals including base-metal sulfides, pyrite, arsenopyrite, Ag-rich electrum and native silver nth Ag sulfides, Ag-Sb-As sulfosalts and Ag tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems in Korea. The Jurassic Au-dominant deposits (orogenic type) were formed at the relatively high temperature $(about\;300^{\circ}\;to\;450^{\circ}C)$ and deep-crustal level $(4.0{\pm}1.5\;kb)$ from the hydrothermal fluids containing more amounts of magmatic waters $(\delta\;^{18}O_{H2O}\;5\~10\%_{\circ})$. It can. It can be explained by the dominant ore-depositing mechanisms as $CO_2$ boiling and sulfidation, suggestive of hypo- to mesothermal environments. In contrast, the Cretaceous Au-dominant $(l13\~68\;Ma),\;Au-Ag \;(108\~47\;Ma)$ and Ag-dominant $(103\~45\;Ma)$ deposits, which correspond to volcanic-plutonic-related type, occurred at relatively low temperature $(about\;200^{\circ}\;to\;350^{\circ}C)$ and shallow-crustal level $(1.0\{pm}0.5\;kb)$ from the ore-forming fluids containing more amounts of less-evolved meteoric waters$(\delta\;^{18}O_{H2O}\;-10\~5\%_{\circ})$. These characteristics of the Cretaceous precious-metal deposits can be attributed to the complexities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epi- to mesothermal environments. Therefore, the differences of the emplacement depth between the Daebo and the Bulgugsa igneous activities directly influence the unique temporal and spatial association of the deposit styles.

• Geophysics and Geophysical Exploration
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• v.2 no.2
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• pp.104-111
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• 1999

As a practical developing step of electromagnetic (EM) tomography technique, we quantitatively analyzed the effects of borehole fluid and casing on the borehole EM responses. The EM response turns out to have nothing to do with the property of the borehole fluid except in the close vicinity of the transmitter, which shows the wide perspective of the application of borehole EM. Single-hole responses in the presence of the steel casing throughly reflect those of the casing itself since its extremely high induction number or shallow skin depth. EM responses through steel casing do show the information of the host medium. In the near field region which corresponds to low frequency or the vicinity of the borehole, however, we can not separate the signal containing the information of the host from that of casing. Otherwise, the severe attenuation of energy in the casing at high frequencies renders the signal undetectable. The optimum frequency is, therefore, to be chosen to extract the information of the host considering both the property of the casing and the skin depth of the medium and the practical technique to determine the casing property through single-hole measurements is required.

• The Korean Journal of Ecology
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• v.24 no.2
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• pp.101-109
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• 2001

We created an environmental forest on the basis of ecological design around the incineration plant of Jindo Engineering and Construction Co., Ltd., which is located in Jeongwang-dong, Siheung-si, Kyunggi-do. To get ecological information of this site, physico-chemical properties of soil on salt marsh, which is located close to the syudy site and of forest soil transported from other sites for ecological restoration were analyzed. Texture of salt marsh and transported soils were loam and sandy loam, respectively. pH, organic matter, T-N, available P, and exchangeable K and Na contents of salt marsh and transported forest soils were 6.7 and 5.4, 4.1 and 0.4%, 1.0 and 0.3mg/g, 46.7 and 6.8ppm, 521 and 207ppm, and 3.8 and 0.5mg/g, respectively. Introduced plants were selected among the dominant species of forests and the species composing the potential natural vegetation around the present study site. Those plants were selected again by considering the tolerances to air pollution and to salt, and their availability. Selected trees were Pinus thunbergii, Sophora japonica, Celtis sinensis, Quercus aliena, Q. serrata, Q. dentata, and Q. acutissima. Selected sub-trees were Albizzia julibrissin, Koelreuteria poniculata, and Styrax japonica and shrubs were Rhododendron yedoense var. poukhanense, R. mucronulatum, Callicarpa japonica, Euonymus alatus, E. japonica, and R. schlippenbachii. On the other hand, introduction of herbs was not considered except for Liriope platyphylla, which was ornamentally planted in one site. Planting bed of mound type was adopted to provide the fine drainage system. Mound was designed to furnish litter, A, B, and C layers simuating the profile of forest soil. Slope of mound was mulched by rice straw of 2cm in thickness to prevent for sliding of litter and soil in cases of strong wind or heavy rain. Height of mound was designed to secure more than 1 m by combining A and B layers. Narrow zones, in which mound with stable slope degree cannot be prepared, was designed to equip the standard soil depth with the introduction of stone for supporting. On the other hand, plants with shallow root system were arranged in some zones, in which satisfactory soil depth cannot be ensured. Plants were arranged in the order of tree, sub-tree, and shrub from center to edge on the mound to make a mature forest of a dome shape in the future. Dispersion of plants was designed to be random pattern rather than clumped one. Problems on creation of the environmental forest by such ecological design were found to be management or inspection by non-specialized project operators and inspecting officers, and regulations for construction without ecological background. Alternative plans to solve such problems were suggested.