• The Korea Journal of Herbology
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• v.21 no.4
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• pp.149-158
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• 2006

Objectives : This study was carried out to characterize the 'Kaolinitum' used as mineral medicine before and after physical and chemical manipulation. Methods : The mineralogy of the original raw kaolinitumes with different localities was identified by X-ray diffraction analysis. The concentrations of major, minor and trace elements of samples, furthermore, measured by the X-ray fluorescence spectrometer (XRF) and inductively coupled plasma-mass spectrometer (ICP-MS). In order to understand the variety of kaolinitum after thermal treatment, the differential thermal analysis (DTA) and the thermo-gravimetric analysis (TGA) were carried out. Results : According to the result of X-ray diffraction analysis, the kaolinitumes are composed ofcalcite, alunite and quartz. Si and Al are the major ions and heavy metals such as Cd, Cr, Pb, Zn, As, Ni and Cu are included in the kaolinitumes as trace ions. The concentration of these metals in the samples decreased after physical and chemical manipulation. The weight of kaolinitum was also decreased at $500^{\circ}C$ and about $700^{\circ}C$during experiment of TGA. Conclusion : The results of this study can be used to provide the scientific basis of the medical usage of kaolinitum.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.180-190
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• 2005

The road slope at Hapcheon-Gun, Gyeongsangnam-Do is under construction, but actual rock quality & discontinuities on the cut slope are something different from the primary design. Therefore, object of this study is to analyze whole engineering-geological characteristics for this slope through site investigation and laboratory analyses because small scale landslides have been occurred during this road construction. For this object, various analyses were performed such as surveying, Schimidt Hammer test, discontinuity investigation and laboratory analysis using DIPS far evaluating slope stability. As the result, it is identified that reinforcement work is needed because plane, toppling & wedge failures will be possibly occurred and seepages are concentrated at several points.

• The Journal of the Petrological Society of Korea
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• v.15 no.1 s.43
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• pp.1-9
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• 2006

Sr isotopic compositions are determined from the syenite of Sancheong area, yielding age of $211{\pm}23(2\sigma)$ Ma and $^{87}Sr/^{86}Sr$ initial ratio of $0.70598{\pm}0.00060$. Such result confirms that Sancheong syenite was emplaced during the Mesozoic around the Triassic-Jurassic boundary. Rather low initial $^{87}Sr/^{86}Sr$ ratio suggests insignificant influence of old crustal materials. There are strong contrast in rock types of plutonic associations between Sancheong-Macheon area and adjacent Hamyang-Geochang area to the north, i.e. syenite-diorite-gabbro and granite-granodiorite respectively. $^{87}Sr/^{86}Sr$ initial ratios also show distinction between these areas. Such differences suggest regional contrast in tectonic environments between them.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.581-592
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• 2013

This article provides an overview on the geothermal energy research in Europe and one of the EU funded projects 'GEISER (Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs)' in which the authors were involved. More details are given for description of GEISER, in particular, about aims and discussions and how the project was managed. Emphasis is given to one of the work packages 'Induced Seismicity and Large Magnitude Events (LME)' and results of this work package are summarized. This article intends to summarize the lessons learned in the GEISER project and give recommendations to future geothermal projects by creating Enhanced Geothermal Systems hydraulic stimulation where induced seismicity issues are expected to be a major issue and obstacle.

• The Journal of the Petrological Society of Korea
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• v.14 no.1
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• pp.38-44
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• 2005

Hornblende $^{40}Ar/^{39}Ar$ age of $113.4{\pm}2.4(2{\sigma})$ Ma was determined from the volcanic pebble of the Silla Conglomerate which belongs to the Hayang Group of the Cretaceous Gyeongsang Supergroup. This age corresponds to the top of Aptian. Based on the reported age information, onset and duration of deposition of the constituting formations of the Hayang Group are constrained as follows; deposition of the Jindong Formation started from ca. 96~97 Ma and lasted for about 15 Ma. Therefore, Jindong Formation was deposited since Cenomanian to Santonian and it is likely to be extended to the early Campanian. We propose 81~80 Ma, which is in early Campanian, as the boundary between Hayang and Yucheon Groups. We suggest that the Silla Conglomerate was deposited during the early Albian and the Haman Formation was deposited during the rest of the Albian and also during the Cenomanian. The Chilgok Formation seems to be deposited during the late Aptian.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.421-434
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• 2005

Abstract Based onthe characteristics of Carlin-type gold deposit in Nevada district, a potential in Korea is evaluated to the Yemi area where is structurally controlled by folds and trust fault. The fault of high angles are combined with a more permeable rocks such as the Yemi breccia and laminated silty limestone. The pattern of enrichment factors for Tl, Sb, As, Ag, Pb, Zn, Cu, Mo and W of limestones in the southern area are geochemically similar with those reported from the Carlin-type Bold deposit. Moreover, the oxygen and carbon isotopes show a hydrothermal alteration is widely developed in this area. According to the result of geophysical interpretation, stable isotope, alteration mineralogy, geochemical study, and geological structure, this mineralized zone may be extended to the M direction, so a detailed systematic exploration is required to identify this alteration zone.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1097-1102
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• 2010

Silver coated copper powders were prepared by a chemical reduction method with controlling the deposition process variables such as the feeding rate of the silver ionic solution and concentration of the reductants at room temperature. The characteristics of the products were evaluated by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic absorption spectrophotometer (AA) and a 4 probe resistivity measurement system. The optimum condition of the preparation of Ag coated Cu powders was at 0.05 M of potassium sodium tartrate and 2 ml/min of the feeding rate of the silver ionic solution. Our method successfully produced dense, uniform, and well-dispersed Ag coated Cu powder of $2{\sim}2.5{\mu}m$ witha silver layer of 100~200 nm. Additionally, we found that thespecific resistivity of the 30 wt.% Ag coated Cu powder was similar to that of pure silver, so that the composite powder could be used as an alternative electromagnetic shielding material for silver.

• Geomechanics and Engineering
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• v.19 no.2
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• pp.167-178
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• 2019

Open-pit (OP) and underground (UG) mining are usually used to exploit shallow and deep ore deposits, respectively. When mine deposit starts from shallow subsurface and extends to a great depth, sequential use of OP and UG mining is an efficient and economical way to maintain mining productivity. However, a transition from OP to UG mining could induce significant rock movements that cause the slope instability of the open pit. Based on Yanqianshan Iron Mine, which was in the transition from OP to UG mining, a large-scale two-dimensional (2D) model test was built according to the similar theory. Thereafter, the UG mining was carried out to mimic the process of transition from OP to UG mining to disclose the triggered rock movement as well as to assess the associated slope instability. By jointly using three-dimensional (3D) laser scanning, distributed fiber optics, and digital photogrammetry measurement, the deformations, movements and strains of the rock slope during mining were monitored. The obtained data showed that the transition from OP to UG mining led to significant slope movements and deformations that can trigger catastrophic slope failure. The progressive movement of the slope could be divided into three stages: onset of micro-fracture, propagation of tensile cracks, and the overturning and/or sliding of slopes. The failure mode depended on the orientation of structural joints of the rock mass as well as the formation of tension cracks. This study also proved that these non-contact monitoring technologies were valid methods to acquire the interior strain and external deformation with high precision.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.187-199
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• 2022

Kriging metamodel, as a flexible machine learning method for approximating deterministic analysis models of an engineering system, has been widely used for efficiently estimating slope reliability in recent years. However, the autocorrelation function (ACF), a key input to Kriging that affects the accuracy of reliability estimation, is usually selected based on empiricism. This paper proposes an adaption of the Kriging method, named as Genetic Algorithm optimized Whittle-Matérn Kriging (GAWMK), for addressing this issue. The non-classical two-parameter Whittle-Matérn (WM) function, which can represent different ACFs in the Matérn family by controlling a smoothness parameter, is adopted in GAWMK to avoid subjectively selecting ACFs. The genetic algorithm is used to optimize the WM model to adaptively select the optimal autocorrelation structure of the GAWMK model. Monte Carlo simulation is then performed based on GAWMK for a subsequent slope reliability analysis. Applications to one explicit analytical example and two slope examples are presented to illustrate and validate the proposed method. It is found that reliability results estimated by the Kriging models using randomly chosen ACFs might be biased. The proposed method performs reasonably well in slope reliability estimation.

• Earthquakes and Structures
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• v.24 no.4
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• pp.303-316
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• 2023

Rapid post-earthquake damage estimation of subway stations is particularly necessary to improve short-term crisis management and safety measures of urban subway systems after a destructive earthquake. The conventional Performance-Based Earthquake Engineering (PBEE) framework with constant earthquake occurrence rate is invalid to estimate the aftershock risk because of the time-varying rate of aftershocks and the uncertainty of mainshock-damaged state before the occurrence of aftershocks. This study presents a time-varying probabilistic seismic risk assessment framework for underground structures considering mainshock and aftershock hazards. A discrete non-omogeneous Markov process is adopted to quantify the time-varying nature of aftershock hazard and the uncertainties of structural damage states following mainshock. The time-varying seismic risk of a typical rectangular frame subway station is assessed under mainshock-only (MS) hazard and mainshock-aftershock (MSAS) hazard. The results show that the probabilities of exceeding same limit states over the service life under MSAS hazard are larger than the values under MS hazard. For the same probability of exceedance, the higher response demands are found when aftershocks are considered. As the severity of damage state for the station structure increases, the difference of the probability of exceedance increases when aftershocks are considered. PSDR=1.0% is used as the collapse prevention performance criteria for the subway station is reasonable for both the MS hazard and MSAS hazard. However, if the effect of aftershock hazard is neglected, it can significantly underestimate the response demands and the uncertainties of potential damage states for the subway station over the service life.