• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.705-713
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• 2016

For the soft ground construction, the factors not considered in the design stage occurs in the construction stage so that they cause the increase of the construction cost due to the structural stability and the design change. The subject of the study is the construction section of the industrial complex access road made in the Ochang region of Chungcheongbuk-do. The study is concerned with selecting the soft ground handling method such as the replacement method using rock debris and the surcharge reflecting the service load as the soft ground handling measure and analyzing the effect of reducing the construction cost with the stability of structures and the reduction of the construction period. The soft ground in the study section consists of sandy and cohesive soil and is 2.4m to 5.5m deep. It is distributed unevenly between the 1.5m to 5.9m stratums under the ground surface. Settlement is not serious, but the future uneven settlement and difference are expected so that the future settlement behavior is estimated by analyzing the site measurement results after the soft ground treatment. Moreover, in consideration of the regional characteristics and economic efficiency, soil with good quality is replaced with rock debris as the replacement material so that 29% of the construction cost is reduced due to the increase of stability and the reduction of duration. If the estimation of the dispersion of the pore water pressure within the dam body and the change of the underground water level and the relation of the actually measured soft ground with consolidation is studied further on the basis of the study, it is expected that the behavior of the soft ground will be correctly estimated in various site conditions.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.2
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• pp.78-84
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• 1995

In 1983, 83 Wenner vertical electrical sounding(VES)s and 22 pumping tests had been carried out by Korea Agricultural Development Corporation(KADC) in Guam Myun, Yeoju Gun, Kyounggi Province. Also, 10 boreholes had been constructed in the area. Using these data electrical and hydraulic properties of aquifer in the Ganam area are investigated in this study. Assuming that the underground is 1-D, VES data are analyzed. Data analysis shows that the subsurface of study area can be interpreted as 4-layer structure and the 3rd layer which is regarded as aquifer has mean thickness of 10 m and mean resistivity of 506 ohm-m and rests on resistive bedrock. Under the circumstances, as most part of electric current flows parallel to the bedding, longitudinal unit conductance is an important parameter controlling VES curves and very closely correlates with transmissivity of aquifer in the study area. Thus, relation between longitudinal unit conductance and transmissivity is investigated in this study. Since resistivity and thickness of each layer are obtained from interpretation of VES data, the relations between transmissivity and resistivity, and between hydraulic conductivity and resistivity are also studied. Studies of such relations show that longitudinal conductance is proportional to transmissivity, and resistivity is inversely proportional to transmissivity and hydraulic conductivity.

• Archives of design research
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• v.19 no.5 s.67
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• pp.351-362
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• 2006

Currently, finding one's way in the underground spaces associated with subway stations in large cities is becoming a serious problem, and an environment that facilitates wayfinding is becoming more important. This study investigated interior treatments that function as visual cues in the subway stations of Seoul, Tokyo, and Taipei in order to develop design guidelines that would improve the place-cognition environment. A theoretical study has shown that there are three categories of visual cue for place cognition: marked trails, regional differentiation, and landmarks. The case study showed that marked trails involve treatments like vertical markers, confrontational positioning, and subway color codes. Regional differentiation involves patterns on the floors and walls, and accent colors on the walls and columns. Landmarks include treatments such as super graphics, symbolic features, artistic decoration and special lights. In the cases of Seoul, marked trails and regional differentiation were predominant. In addition, the Olympic symbol 'Hodori' and the ancient Korean character "Hunminjungeum" were used as landmarks. In the cases of Tokyo, regional differentiation predominated over marked trails because of the complexity of the spatial structure and subway line connection system. In the cases of Taipei, simple, unified images predominated, and there was minimal dependence on marked trails and landmarks. The need for regional differentiation was weak, because the stations studied have open structures that guarantee an open field of view. The results of this research could be used as design guidelines, after further experimental verification, that would help to improve the public environment in terms of wayfinding.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.6
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• pp.1-19
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• 2017

This study set out to identify problems with amphibian habitation by the wetland types and improve their habitation environment in urban forest wetlands, thus creating a habitat for amphibians. Study site include forest swamps in Jatjul Park as well as Yeoji neighborhood Park in Guro-gu, and in Choansan neighborhood Park in Dobong-gu. The forest swamp in Jatjul Park gets its water from Mt. Maebong and it is a former escalated farmland-turned wetland. The swamp area is $2,500m^2$, a forest zone and a landscape planting site are 83.27% and 6.70% each. Target species Seoul pond frogs are inseparable from rice fields because they live in a short radius of and lay eggs in or near paddy fields, and Rana nigromaculata have similarities with Rana plancyi chosenica in choosing their habitats. There was need for paths that would lead to other paths so amphibians would spread to other parts of the forest and for measures to secure open water. Modifying a variety of routes for water, human and animals along with building a buffer to keep the core habitation zones were required. The forest swamp in Yeonji neighborhood Park used to be a water reservoir on the foot of Mt. Gunji. The swamp area is $1,980m^2$, a forest zone and farmland account for 80.61% and 4.88% each. Non-point pollutants from upstream along run into the subject forest marsh, bare ground on the around swamp and steep stone embankments obstructed amphibians. Target species was Bufo gargarizans that live in forests and edges of hills and spawn in deep water. The forest swamp in Choansan neighborhood Park gets its water from Mt. Choan and it is close to its water source that it is a mountain stream forest wetland. The basin and the swamp are $35,240m^2$ and $250m^2$ in size respectively. A forest zone accounts for 90.20%, high stone embankments laid in refurbishing the valley obstruct amphibians and there is water shortage in times of droughts. Target species were Rana coreana, Rana dybowskii and Hynobius leechii that live in mountain valleys, streams and wetlands and lay eggs in forest marshes and rocks in valleys. Looking into the three swamps of amphibian habitation, I came to conclusions that those wetlands were suitable for their amphibians but man-made facilities blocked their corridors leading to other corridors and even killed off target species in some parts of those swamps by destroying those parts. Amphibians live in water, on ground and underground at different stages of life. Hence, we should take this fact into consideration when planning their habitats and design core habitation zones, buffers zone and use zones accordingly. Buffer zones ought to be between core habitation zones and surrounding trees. Aiming at protecting core habitation zones, buffers should be in harmony with habitation zones. Use zones should be minimized in size and not in direct contact with core habitation zones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.680-687
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• 2018

Borehole radar is a radar used for underground resources and geological exploration purposes. It needs a high-speed sampler to transmit electromagnetic waves with a pulse width of several ns and to receive reflected waves of several tens to several hundreds of MHz reflected from the object to be surveyed. ETS (Equivalent-Time Sampling), which can achieve sampling performance of several GHz with a sampling frequency of several tens of MHz, is suitable for use as a sampler of a borehole radar receiver. In this paper, we propose a method to control the sampling clock delay, which is the most important factor in ETS sampler design, using four clocks with phase difference of $90^{\circ}$ for one clock source. The proposed method can reduce the time required to acquire the data within the set interval by 1/25 than the conventional method using the delay generator. When the implemented sampler is applied to the receiver of existing borehole radar, it is possible to accumulate 58 additional times due to the shortened sampling time. In addition, by using one delay control logic compared with the conventional method using several sampling clock delay control logic in order to satisfy the target sampling range, it is possible to omit the correction process which was necessary in the past. As a result, the structure of the system can be simplified and a uniform sampler can be realized.

• Journal of the Korean Geophysical Society
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• v.6 no.3
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• pp.139-153
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• 2003

Subsurface information is one of the most important factors in the archaeological excavation. To obtain the information on the underground, geophysical prospecting is becoming a popular method. This study is on the small rocky islands located 200m away from the shoreline of Gampo, Gyeongju city, Korea. According to the historical records and field surveys, it was revealed as the tomb of King Munmu of Shilla Dynasty. However, the questions and debates, such as whether it is really the tomb of King Moonmu or not, and whether it is a buried place or not, are still remains, in addition to the incompletion of precise surveying and scientific studies. The scope of this study contains the researches on the above problems and debates using the geophysical and geological methods and techniques. The rocky islands around the submerged Tomb of King Moonmu is composed of granite, and sag exists inside of the islands. Sea water enters through the east groove by wave and is drained to the west slot by hydraulic gradient, since west slot is 15cm lower than the east. Sag inside of the islands is believed to be extended and widened from pre-existed sinkage by applying tools like chisel in the joints and cracks. It is concluded that the submerged megalith inside of sag was from the rock block which was developed by joints. Geophysical surveys reveal that there is no artificial structure or stone/china/steel chest, under the m egalith and rocky island. Researches show that the tomb of King Moonmu was constructed in the small rocky island artificially. However, the evidences show that planners and constructors of the tomb made every possible effort to preserve the natural environment and condition. It is strongly believed that the megalith was sort of alter to sprinkle bone-ash rather than buried place.

• Journal of Korea Water Resources Association
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• v.53 no.4
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• pp.303-312
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• 2020

An underground deep tunnel system is a facility in form of a reverse siphon for an under flood defense structure. In this study, the 'Shinwol rainwater storage and drainage system', which is under construction for the first time in South Korea, in order to confirm the effects of undular bore and pressurized air on the hydraulic stability of the facility in various flood scenarios a hydraulic model experiment was performed. As a result of this study, it was analyzed that the undular bore generated downstream pushed the pressurized air collected in the facility while moving upstream, and the pressure inside the pipe increased at this time. It was analyzed that the pressure during the passage of the undular bore was greater than the sum of the static pressure and dynamic pressure at the time and overflow occurred when the cross-sectional size of the pressurized air was more than 40% of the cross sectional area of the tunnel. It is determined that this is correlated with the volume of pressurized air collected in the facility, and it is determined that it is necessary to study the relationship between velocity of undular bore and the volume of pressurized air in the future.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.441-450
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• 2006

The on-land seismic survey in Korea was begun in mid-1960s. Kim et al.(1967) of Korea Geological Survey reported on the result of gravity and seismic reflection surveys conducted in the Pohang area for the period of 1963-64 to assess its possibility of oil entrapment. Hyun and Kim (1966) carried out a refraction survey on the tunnel wall. Since then, the KGS geophysicists had conducted seismic surveys on Kyungsang sedimentary basin as a main project for several years. In 1970s, on-land seismic surveys had been conducted for various purposes such as site investigation for the nuclear power plants and industrial complex, exploration for ground water, mineral resources and underground tunnel. The first reflection survey with CMP acquisition was attempted in 1978 by using a digital recording system. But most of on-land seismic surveys had employed the refraction method until 1980s. In 1990s, high resolution reflection and various borehole seismic surveys such as tomography, uphole, downhole, cross-hole methods have been attempted by universities and engineering companies. The applications of on-land seismic surveys have been enlarged for both academic and industrial purposes such as investigation of geologic structure of the fault and tidal flat area, construction of highway, railroad and dam, geothermal energy and mineral resource exploration, environmental assessment for waste disposal sites and archaeological investigations. In 2002, the first crustal seismic survey was carried out on the profile of 294km length across the whole peninsular. It is expected that the advanced technology and experience acquired through offshore seismic surveys, which have been conducted in continental shelf of Korea and foreign oil fields, will stimulate the more active on-land seismic explorations.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.346-353
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• 2012

Multi-specimen uniaxial compression test has been carried out in order to find the method to determine the five independent elastic constants from a single standard specimen of a transversely isotropic rock. Total 35 specimens of 7 different angles from a large block of rhyolite presenting the flow structure obviously are used in tests. This second report is to focus on the statistical evaluation of measured strains and analyzed elastic constants. And the determination of their true or near-true values is discussed. As the result of RSD analysis, it turns out that the reliability of measured strains is sufficiently obtained and Saint-Venant approximation is well applicable except 15 degree angled specimen in tests. RSD is decreasing on the increase of the angle of anisotropy. This tendency may be caused not only by the decreasing of the deviation of measured strains, but also by the better applicability of Saint-Venant approximation on the increase of angle. It can be concluded that the analyzed values are considered the near-true ones of five independent constants on the high reliability. But the variation of the apparent Young's modulus expected by these values is not proved to match the measured tendency. It is inferred that the factor to decrease the apparent Young's modulus and/or to increase the shear strain, is present in the test or in the nature of the anisotropy in consideration of this inconsistency.

• Tunnel and Underground Space
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• v.30 no.5
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• pp.462-472
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• 2020

Rock classification is fundamental discipline of exploring geological and geotechnical features in a site, which, however, may not be easy works because of high diversity of rock shape and color according to its origin, geological history and so on. With the great success of convolutional neural networks (CNN) in many different image-based classification tasks, there has been increasing interest in taking advantage of CNN to classify geological material. In this study, a feasibility of the deep CNN is investigated for automatically and accurately identifying rock types, focusing on the condition of various shapes and colors even in the same rock type. It can be further developed to a mobile application for assisting geologist in classifying rocks in fieldwork. The structure of CNN model used in this study is based on a deep residual neural network (ResNet), which is an ultra-deep CNN using in object detection and classification. The proposed CNN was trained on 10 typical rock types with an overall accuracy of 84% on the test set. The result demonstrates that the proposed approach is not only able to classify rock type using images, but also represents an improvement as taking highly diverse rock image dataset as input.