• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.131-137
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• 2016

In this paper, a feasibility on a ground-penetrating radar for detecting subsurface cavities near buried pipes has been investigated. The experimental setup was implemented by employing an impulse ground-penetrating radar system, a xy Cartesian coordinate robot, an underground material filled tank, a metal pipe and a simulated cavity model. In particular, the simulated cavity model was constructed by packing Styrofoam chips and balls, which have both similar electrical properties to an air-filled cavity and a solid shape. Through typical three experiments, B-scan data of the radar have been acquired and displayed as 2-D gray-scale images. According to the comparison of B-scan images, we show that the subsurface cavities near the buried pipes can be detected by using the radar survey.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.581-586
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• 2011

This study describes a hydrogen embrittlement evaluation of the subsurface zone in 590DP steel by micro-Vickers hardness measurement. The 590DP steel was designed to use in high-strength thin steel sheets as automotive materials. The test specimens were fabricated to 5 series varying the chemical composition through the process of casting and rolling. Electrochemical hydrogen charging was conducted on each specimen with varying current densities and charging times. The relationship between the embrittlement and hydrogen charging conditions was established by investigating the metallography. The micro-Vickers hardness was measured to evaluate the hydrogen embrittlement of the subsurface zone in addition to the microscopic investigation. The micro-Vickers hardness increased with the charging time at the surface. However, the changing ratio and maximum variation of hardness with depth were nearly the same value for each test specimen under the current density of 150 mA/$cm^2$ and charging time of 50 hours. Consequently, it appears that hydrogen embrittlement in 590DP steel can be evaluated by micro-Vickers hardness measurement.

• Journal of the Korean GEO-environmental Society
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• v.23 no.10
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• pp.21-31
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• 2022

Prospecting ice on Moon requires drilling systems to obtain subsurface samples and measure composition of ice deposits. Landers and rovers need to be equipped with drilling equipment in order to analyze the ice and subsurface resources located at the poles of Moon. These devices must be small, lightweight, low-power, highly efficient and high-performance units in order to function properly under the extreme conditions of the lunar environment. Researchers have developed a prototype drilling apparatus that is able to operate in atmospheric and cold environments. Newly developed drilling system in Korea, which is capable of performing not only sampling but also subsurface investigation, is introduced.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.3
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• pp.214-220
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• 2007

The effects of soil percolation rate on $CH_4$ and $N_2O$ emissions were investigated from paddy fields with different drainage systems. Subsurface tile drainage plot of soil percolation rate $11.9mm\;d^{-1}$ and non-subsurface drainage plots of soil percolation rate $7.4mm\;d^{-1}$ and $6.9mm\;d^{-1}$ were designed. The effects of rice straw application were measured at each drainage plots. The subsurface tile drainage plot of soil percolation rate $11.9mm\;d^{-1}$ showed the lower emission amount both of $CH_4$ and $N_2O$ among treatments. In the subsurface tile drainage plot of $11.9mm\;d^{-1}$ percolation rate, 46% of $CH_4$ and 33% of $N_2O$ emission amounts were reduced in comparison of non-subsurface drainage plot of $6.9mm\;d^{-1}$ percolation rate. With rice straw application, the $CH_4$ emission amount was 2.1 times to that from no-applied plot, the $N_2O$ emission amount was not affected by rice straw application.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.4
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• pp.170-180
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• 2010

With development of the earth's subsurface space, the need for a reliable subsurface spatial model such as a cross-section, boring log is increasing. However, the ground mass was essentially uncertain. To generate model was uncertain because of the shortage of data and the absence of geotechnical interpretation standard(non-statistical uncertainty) as well as field environment variables(statistical uncertainty). Therefore, the current interpretation of the data and the generation of the model were accomplished by a highly trained experts. In this study, a geotechnical ontology model was developed using the current expert experience and knowledge, and the information content was calculated in the ontology hierarchy. After the relative distance between the information contents in the ontology model was combined with the distance between cluster centers, a cluster analysis that considered the geotechnical semantics was performed. In a comparative test of the proposed method, k-means method, and expert's interpretation, the proposed method is most similar to expert's interpretation, and can be 3D-GIS visualization through easily handling massive data. We expect that the proposed method is able to generate the more reasonable subsurface spatial information model without geotechnical experts' help.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.51-56
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• 2005

To understand the chemical changes in the streamwater and contribution of subsurface discharge during the storm event, we analyzed electric conductivity (EC), anions, and cations in Gwangneung deciduous and coniferous forest catchment. The stream water samples were collected three times in 2004 by using an auto-sampler: September 7-9 (E040907-D and -C; where D and C indicate deciduous and coniferous forest catchment, respectively), September 11-13 (E040911-D and -C), and September 16-18 (E040916-D and -C). We found a negative relationship between discharge intensity and EC in streamwater. The E040911 and E040916 showed slack change of stream discharge in comparison to E040907 due to contribution of base flow recharged by much precipitation. Moreover, NO/sub 3//sup -/ concentrations in E040911-C were highest, which may have resulted from forest management such as thinning in 2004. The relationship between pH and alkalinity in stream water showed that much of stream water have been recharged through subsurface. We conclude that subsurface discharge highly influences streamwater quality in a forested catchment, and the seperation of stream water discharge is therefore necessary to sustainable water management.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.219-228
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• 2006

In urban areas, tunnelling induced ground deformations, particularly ground settlements should be considered in order to minimize the damage of adjacent structures. Therefore, an appropriate monitoring system for the tunnel construction should be setup at the planning or design stage. A number of studies on ground settlements due to tunnelling in soft ground have been carried out so far. However, most studies have focused on clay soil rather than sand soil. In particular, a few studies on behaviour of subsurface deformations in granular material have been reported. In this study, two-dimensional laboratory model test with aluminium rods regarded as continuum granular material and close range photogrammetric technique, and numerical analysis were carried out in order to identify the behaviour of subsurface deformations due to shallow tunnelling. Direction and magnitude of displacement vectors from the model test was identical to the numerical analysis. In particular, the vector direction was appeared to be toward a point below the tunnel invert level. A narrow 'chimney or tulip like' pattern of vertical displacement was confirmed by both the model test and numerical analysis. This is consistent with the field data. In addition to the qualitative comparison, the quantitative comparison of subsurface settlements according to 2D volume loss showed good agreement between the model test and numerical analysis. Therefore, close range photogrammetric technique applied in the model test may be used to validate the result from the continuum numerical analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1150-1156
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• 2007

In this paper, two novel subsurface antennas for remote management of underground facilities using PCS and cellular wireless network are proposed. The proposed subsurface antenna is a dual band circular patch which is inserted and molded for the protection of the antenna into a metal such as a manhole cover. The antenna is designed considering the resonant frequency shift of the antenna due to the insertion and molding. The measured return loss and receiving power of the fabricated antenna comparison with a dipole shows that two proposed subsurface antenna can be used for remote management of underground facilities using PCS and cellular systems.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.393-398
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• 2007

Seismic traveltime tomography technique was conducted at a site composed of black shale. It is well known that black shale has strong anisotropic property. Therefore, the anisotropic property of black shale has to be considered to obtain the appropriate subsurface velocity model by an inversion process. To estimate the anisotropic constant of the velocity of the black shale in the survey area, the relation between the velocity, which is calculated by the straight ray path and the first arrival time, and the angle of the ray propagation was examined. The elliptically shaped relation was found and it reveals that the black shale contains the anisotropic property of velocity. It was also noticed that the horizontal velocity is faster than the vertical velocity. When the estimated anisotropic constant was applied in the process of the velocity inversion for three sets of field data, we could obtain the appropriate velocity structures of the site that is consistent with the result of the geological survey.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.59-63
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• 2008

The surface runoff is one of the important components for the surface water balance. However, most Land Surface Models(LSMs), coupled to climate models at a large scale for the prediction and prevention of disasters caused by climate changes, simplistically estimate surface runoff from the soil water budget. Ignoring the role of surface flow depth on the infiltration rate causes errors in both surface and subsurface flow calculations. Therefore, for the comprehensive terrestrial water and energy cycle predictions in LSMs, a conjunctive surface-subsurface flow model at a large scale is developed by coupling a 1-D diffusion wave model for surface flow with the 3-D Volume Averaged Soil-moisture Transport(VAST) model for subsurface flow. This paper describes the new conjunctive surface-subsurface flow formulation developed for improvement of the prediction of surface runoff and spatial distribution of soil water by topography, along with basic schemes related to the terrestrial hydrologic system in Common Land Model(CLM), one of the state-of-the-art LSMs.