• The Journal of Engineering Geology
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• v.27 no.1
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• pp.81-90
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• 2017

Preceding displacements in tunnel are difficult to predict since the measurements of displacements after excavation can not be performed immediately. In the present study, The longitudinal displacements which can be measured immediately after excavation are used to predict the crown settlements occurring before excavation only if fault is located at the tunnel crown. Three-dimensional finite element analysis was conducted using 28 numerical models with various fault attitudes to analyze the correlation between the longitudinal displacements on tunnel face and preceding crown settlements. The results, $L_{face}/C$ ratio show 2~12% in the drives with dip models and 2~13% in the drives against dip models individually. In addition, each model has a certain $L_{face}/C$ ratio. The result of the regression analysis show that the coefficient of determination is over 0.8 in most models. Therefore, crown settlements occurring before excavation can be predicted by analyzing the longitudinal displacements occurring on tunnel faces.

• Geophysics and Geophysical Exploration
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• v.4 no.4
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• pp.124-132
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• 2001

Electrical resistivity survey has been conducted for delineating geological fault structure in Kaekok-ri near Kyungju. In general, electrical resistivity survey has an advantage of searching buried faults and its traces compared with other geophysical survey methods. Distribution of electrical conductivity in the ground is influenced by the ratio of pores, groundwater and clay minerals. These properties are evidenced indirectly to explain for weathering condition, faults and fracture Bones. Thus the electrical resistivity survey can be an effective method to find buried faults. We have carried out two dimensional (2-D) interpretation by means of smoothness-constrained least-squares and finite element method. Field data used in this paper was acquired at Kaekok-ri, Wuedong-eup, Kyungju-si, where is Ulsan Fault and is close to the region in which debatable quaternary fault traces were found recently. The dipole-dipole array resistivity survey which could show the 2-D subsurface electrical resistivity structure, was carried out in the area with three lines. The results showed good property of fault, fracture zone and fault traces which we estimated were congruous with the results. Through this study, 2-D electrical resistivity survey interpretation for fault is useful to apply.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5123-5127
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• 2011

Research and development for the technology, that is about maintenance and accidents prevention of underground power distribution line, are demanding. The precise detection of leakage point of underground power line is very important, because it is difficult to detect the exact location of a fault in underground power line and to repair faults. When earth electric potential is measured to detect underground electric leakage point after transmitting AC electric pulse wave to underground power line, it must be measured in a specific half period of AC pulse wave because the distribution of the electric earth potential varies with the polarity of the transmitted wave. In this paper we proposed the measurement of half period modulated earth potential as a method to detect a underground leakage point. And We compared the proposed method with other methods. Through experiments we verified that the proposed method can be implemented and operated properly.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.5
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• pp.383-390
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• 2008

The SCR in Static Transfer Switch (STS) is used for reliability improvement of important load's power supply in industry field. However an average of 2% fault in thyristor(SCR) occurs, so that the attached mechanical switch is paralleled with SCR's both end points and SCR operates only during the $12{\sim}208$[mS] before operation of the mechanical switch. Also, an ISC (Ideal State Conditioning Interlock Device) - STS system that two power supply paths may not be thrown at the same time is developed to remove the overlap section perfectly when a short or earth fault is generated in one system. This method has reduced the fault rate remarkably through the reduction of SCR's fatigue degree by using SCR in conversion operation corresponding to 0.89 times a year. Also, in case of fault generations, it does not affect to supply power to the load, therefore it contributes to the promotion of reliability in the power supply.

• Fire Science and Engineering
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• v.27 no.2
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• pp.1-5
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• 2013

This paper studies on an arc fault interruption control circuit (AFICC) of fault voltage sensing type. The proposed voltage sensing type AFICC (VST_AFICC) is an electrical fire prevention apparatus that operates the existing circuit breaker with sensing the instantaneous voltage drop of line voltage when occurs electrical faults. The existing Earth Leakage Circuit Breaker (ELB), Molded_case Circuit Breaker (MCCB), and Residual Current Protective Devices (RCDs) used in low voltage distributing system don't have protective capability from electric arc faults to be a major factor of electrical fire. In this paper to improve such problems, a new VST_AFICC using the distortion of voltage waveform when occurs electrical faults is proposed to prevent electrical fire. There is characteristic that the control method of proposed apparatus is different from previous current sensing type. The proposed AFICC has merit that is manufactured by small size and light weight. The practicality of a new VST_AFICC is also verified through various operation analysis.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.181-188
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• 2012

The 1M and $2M_1$ stacking sequences are the most frequently encountered in the illite species among the possible 6 polytypes. The $1M_d$, derived from the 1M polytype which exhibits a variable degree of disorder in the stacking sequence, is also observed in illite samples. In this paper, the author introduces and reviews the theoretical background of the quantitative analysis method of illite polytypes, and considers the possibility to determine the fault age and its reactivation age using K/Ar age-dating based on the quantification of illite polytypes in the fault system. For the increase of the accuracy and precision of the illite age analysis method, the occurrence, identification, and mineralogical characterization of illite polytypes should be defined in detail. The broadening effect of (hkl) reflections, due to disordering of 1M polytype and the presence of I/S minerals with expandability, are also considered as the main parameters controlling the quantification of illite polytypes using the WILDFIRE(C)simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2267-2273
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• 2009

In this paper, in order to monitor and manage an electrical risk factor like as leakage current, load current, and arc-fault, a real time monitoring and management system being operated in the ubiquitous environment was developed, and a plan of construction of an electrical safety grid using the system was proposed. For confirmation of usefulness and reliability of the proposed safety system and grid, the developed intelligent panels were applied to 28 Korean traditional houses in Jeonjoo city, and the grid including the panels was operated. If the proposed National Electrical Safety Grid is completely constructed in the houses of general electrical users, the Grid will have an effect on that a main manager on electrical safety transfers from management system by general people to real-time management system by expert. As a result, the electrical fires caused by an over-load, an arc-fault, and an earth-fault will be prevented.

• Journal of the Korean earth science society
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• v.32 no.2
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• pp.161-169
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• 2011

Focal mechanism solutions in the central and western areas of the Korean Peninsula (36-37.8$^{\circ}N$, 126-128$^{\circ}E$) were obtained from the analysis of the recent seventeen earthquakes (M${\geq}$2.2) which occurred from January, 2005 to May, 2010. The spatial differences between the epicenters recalculated by this study and those announced by the Korea Meteorological Administration are less than $0.03^{\circ}$, indicating a small deviation. Focal mechanism solutions were obtained from the analysis of P wave polarities, SH wave polarities and SH/P amplitude ratios. The focal mechanism solutions show dominant strike-slip faulting or oblique slip faulting with strike-slip components. The P-axes trends are mainly ENE-WSW or E-W directions. The direction of fault plane and auxillary fault plane with NNE-SSW and WNW-ESE are almost parallel to the general trends of lineaments in the study area. The results also show that focal mechanism solutions and the main axis of stress field in the Kyonggi massif and Okchon belt are almost same.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.548-559
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• 2011

3-D Multi-geophysical surveys were carried out around the Hwasan caldera at the Euisung Sub-basin. To overcome the limitations of resolutions in previous studies, dense gravity data and magnetotelluric (MT) data were obtained and analyzed. In this study, the independent inversion models from gravity and MT data were integrated using correlation and classification approaches for 3-D imaging of the geologic structures. A Structure Index (SI) method was proposed and applied to the integration and classification analyses. This method consists of Type Angle (TA) and Type Intensity (TI) values, which are estimated by the spatial correlation and abnormality of the physical properties. The SI method allowed the classification analysis to be effectively performed. Major findings are as follows: 1) pyroclastic rocks around the central area of the Hwasan caldera with lower density and resistivity than those of neighboring regions extended to a depth of around 1 km, 2) intrusive igneous rocks with high resistivity and density were imaged around the ring fault boundary, and 3) a basement structure with low resistivity and high density, at a depth of 3-5 km, was inferred by the SI analysis.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.1-12
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• 2024

South Korea's mining industry was actively developed until 1980, but subsequent declining profitability forced many mines to close. Most of the abandoned mines are susceptible to persistent subsidence because of the length of time since mining ceased. Accurate prediction of the locations and times of subsidence is difficult; therefore, this study aims to apply continuum analysis to past cases of subsidence to establish a method of predicting the location and magnitude of future subsidence. The study area is an area of ○○ mining located between the Yangsan fault zone and the Moryang fault zone, in which three subsidence events occurred between 2005 and 2009. Drilling surveys and electrical resistivity surveys were performed at subsidence sites determined the distribution of strata, and through laboratory tests obtained the physico-mechanical properties of the rock. Numerical analysis of the results found that the plastic status area includes the areas of actual subsidence and that continuum analysis can also be used to predict the location and magnitude of subsidence caused by mine goaf.