• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.177-186
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• 2005

World widely, the occurrences of earthquakes have been increased recently including to nations which earthquake often happen to like Japan. Taking into account that the earthquake acceleration at design was 0.154 g at the contigency level earthuake (CLE) with its geological condition, it resulted that this method must be the most efficient condition against the earthquake vibration to two lane cut-and cover tunnel. The correlations between the result of the shaking table test and its numerical analysis showed that the test data of the bending stress due to the earthquake vibration have been underestimated about 5 percents in case of the cut slope 1 : 0.6 and about 10 percent in case of the cut slope 1 : 1.2. However, on average, the results showed a similar tendency that the higher the height of the backfill of the EPS block was, the less the bending stress was.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.267-272
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• 2005

Geophysical surveys were performed in three abandoned mines: Jangpoong, Kwangyang, Imchon. The main objectives of the researches include delineating the pathways of leachate from acid mine drainage(AMD), mapping buried rock wastes and tailings, detecting drainage pipes, and investigating the gallery and membrane, if they exist, Geophysical responses were well correlated with the results from water sample data(i.e., pH, EC, heavy metal contents, $SO_4^{-2}$). Main pathways of the leachate were successfully detected in electrical resistivity sections and self-potential(SP) profiles, whereas waste rocks, drainage pipes, and membranes were effectively located by incorporating seismic refraction, electrical resistivity and GPR methods.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.197-202
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• 2005

The electromagnetic signals associated with the seismic activity in the south-east offshore of Kii peninsula, Japan, were clearly recorded at the MT sites in Jeju island, Korea. In this research, we have identified the co-seismic electromagnetic signals associated with the seismic activity and have analyzed the characteristics of significant electromagnetic variations. The analysis of phase velocity, power spectral density, MT impedance and polarization direction shows that the significant earthquake signals have the frequency band of about 0.05 to 0.5 Hz and that the sources of electromagnetic field are local effects of passing seismic waves. The simple approximation using electrokinetic effect successfully explains the co-seismic EM signals coincides with measured data but cannot explain the localities of electromagnetic variations.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.117-127
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• 2011

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.155-162
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• 2014

We performed MCNP modeling for density log, and examined its reliability and validity comparing the correction curves from physical borehole model. Based on the constructed numerical model, numerical modelings of density sonde in three-inch borehole were carried out under the various conditions such as the existence and type of casing or fluid, and also the stand-off between the sonde and borehole wall. These results of numerical modeling quantitatively reflect effects of casing and fluid in borehole, and moreover, demonstrate constant patterns with interval change from borehole wall. From this study, numerical modeling using MCNP shows a good applicability for well logging, and therefore, can be efficiently used for the calibration of well logging data under the various borehole conditions.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.147-154
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• 2014

For analyzing the distribution of chromite, magnetic survey was carried out on the chromium mineralized belt in Bophi Vum area, northwestern Myanmar. As a result, the magnetic susceptibility of chromite is lower than those of dunite and harzburgite, which are background rocks of chromite. Also, the locations of low magnetic anomaly zone and low magnetic susceptibility models of 3D magnetic inversion result are spatially well matched with those of chromite occurrences confirmed by the surface geological survey and trench survey. Some of low magnetic effects are expanded to the periphery area of chromite occurrences. Considering the magnetic susceptibility characteristics of various rocks in this area, the expanded low magnetic anomaly zones are estimated as the high potential areas bearing chromite. For confirming the potential area of chromite pointed by coarse magnetic survey, the additional detail exploration need to be carried out in future.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.713-725
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• 2005

The objective of this study is to evaluate the applicability and simulation capability of PRMS, developed by U.S. Geological Survey, over the seven multi-purpose dam watersheds in Korea. The basic concepts of model components and their parameters are investigated for the evaluation of model applicability and the possibility of model parameter estimation is suggested based on the data availibility. For model parameter estimation, some parameters are directly estimated from measurable basin characteristics, but the others are estimated by Rosenbrock's automatic optimization scheme. The results show that the simulated flows from the model were very close to the observed ones. Although the default values for snowmelt model parameter are used, the results from snowmelt simulation is also acceptable. The model shows that the simulation capability is not sensitive to the basin size, however, according to increasing basin area, simulation characteristics are close to those for lumped model rather than semi-distributed model.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.3 s.33
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• pp.53-57
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• 2005

The moors ecosystem is sensitive environment change and weak in artificial interference. These nature property are very important to people. It is necessary to preservation and protection the moors with a countermeasure. We really need to Environment-GIS(E-GIS) using Geographical Information System(GIS) and digital map including range, correct position and attribute data of moors. In this study, we take priority of making a database of moors management. Taking effect an environment assesment, we concentrate on a standard method of digital map production and a preservation of moors in our research using GIS. Especially, we have to preserve our important national heritage using GIS when Environment Assesment is conducting under construction. We suggest to pre-estimated model of hidden moors as analysing terrain, geological feature, a geographical distribution of plants and animals using GIS.

• Geophysics and Geophysical Exploration
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• v.8 no.2
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• pp.119-128
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• 2005

The assessment of erosional and depositional patterns near bridge piers is essential to understand the fluvial scour process. Geophysical surveys are particularly effective in determining the riverbed variations in a river and may also be of value for obtaining the previous scour history below the riverbed profile. In this study, GPR (Ground Penetrating Radar), as a non-destructive geophysical technique, was used to assess the existence and depth of existing and infilled scour thickness, streambed materials, and pre- and post- scour surfaces at the bridge piers in Han River, June 2002 and October 2002. The GPR acquisition system used for obtaining profiles of the shallow subsurface deposits was a portable GSSI SIR 2000 system with 100 and 400 MHz antennas. The GPR data obtained along the 24 bridge piers in the flow direction of the river and in the surroundings of 5 bridge piers were compared and presented in this study. It is concluded that GPR surveys can be effective in determining both the water depth and sub-bottom geological structure near the bridge piers and abutments provided that the appropriate instrumentation and operational procedures are applied.

• Geophysics and Geophysical Exploration
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• v.4 no.4
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• pp.110-114
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• 2001

In order to obtain the geological information of the shallow subsurface and the characteristics of resistivity curves to the lateral extent of the gold bearing gravel layer underlaid by a thick layer, electrical resistivity surveys had been carried out in the northern area of Takaoi village, Kalimantan, Indonesia from September 30th to October 27th in 1999. The Dipole-Dipole (Dp-Dp) resistivity survey was carried out with a electrode spacing of A=3m, 5m and electrode separation index n=10, and the vertical electrical sounding (VES) of the Schlumberger type was performed at 6 sites. The interpretation of the Dp-Dp data and VES curves by computer modeling indicates 5 classified layers as the horizontal structure. And the characteristics of VES curves shows us KH type.